canvas.js

/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */
/* Copyright 2012 Mozilla Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/* globals error, PDFJS, assert, info, shadow, TextRenderingMode,
           FONT_IDENTITY_MATRIX, Uint32ArrayView, IDENTITY_MATRIX, ImageData,
           ImageKind, isArray, isNum, TilingPattern, OPS, Promise, Util, warn,
           getShadingPatternFromIR, WebGLUtils */

'use strict';

// <canvas> contexts store most of the state we need natively.
// However, PDF needs a bit more state, which we store here.

// Minimal font size that would be used during canvas fillText operations.
var MIN_FONT_SIZE = 16;
var MAX_GROUP_SIZE = 4096;

var COMPILE_TYPE3_GLYPHS = true;

function createScratchCanvas(width, height) {
  var canvas = document.createElement('canvas');
  canvas.width = width;
  canvas.height = height;
  return canvas;
}

function addContextCurrentTransform(ctx) {
  // If the context doesn't expose a `mozCurrentTransform`, add a JS based on.
  if (!ctx.mozCurrentTransform) {
    // Store the original context
    ctx._scaleX = ctx._scaleX || 1.0;
    ctx._scaleY = ctx._scaleY || 1.0;
    ctx._originalSave = ctx.save;
    ctx._originalRestore = ctx.restore;
    ctx._originalRotate = ctx.rotate;
    ctx._originalScale = ctx.scale;
    ctx._originalTranslate = ctx.translate;
    ctx._originalTransform = ctx.transform;
    ctx._originalSetTransform = ctx.setTransform;

    ctx._transformMatrix = [ctx._scaleX, 0, 0, ctx._scaleY, 0, 0];
    ctx._transformStack = [];

    Object.defineProperty(ctx, 'mozCurrentTransform', {
      get: function getCurrentTransform() {
        return this._transformMatrix;
      }
    });

    Object.defineProperty(ctx, 'mozCurrentTransformInverse', {
      get: function getCurrentTransformInverse() {
        // Calculation done using WolframAlpha:
        // http://www.wolframalpha.com/input/?
        //   i=Inverse+{{a%2C+c%2C+e}%2C+{b%2C+d%2C+f}%2C+{0%2C+0%2C+1}}

        var m = this._transformMatrix;
        var a = m[0], b = m[1], c = m[2], d = m[3], e = m[4], f = m[5];

        var ad_bc = a * d - b * c;
        var bc_ad = b * c - a * d;

        return [
          d / ad_bc,
          b / bc_ad,
          c / bc_ad,
          a / ad_bc,
          (d * e - c * f) / bc_ad,
          (b * e - a * f) / ad_bc
        ];
      }
    });

    ctx.save = function ctxSave() {
      var old = this._transformMatrix;
      this._transformStack.push(old);
      this._transformMatrix = old.slice(0, 6);

      this._originalSave();
    };

    ctx.restore = function ctxRestore() {
      var prev = this._transformStack.pop();
      if (prev) {
        this._transformMatrix = prev;
        this._originalRestore();
      }
    };

    ctx.translate = function ctxTranslate(x, y) {
      var m = this._transformMatrix;
      m[4] = m[0] * x + m[2] * y + m[4];
      m[5] = m[1] * x + m[3] * y + m[5];

      this._originalTranslate(x, y);
    };

    ctx.scale = function ctxScale(x, y) {
      var m = this._transformMatrix;
      m[0] = m[0] * x;
      m[1] = m[1] * x;
      m[2] = m[2] * y;
      m[3] = m[3] * y;

      this._originalScale(x, y);
    };

    ctx.transform = function ctxTransform(a, b, c, d, e, f) {
      var m = this._transformMatrix;
      this._transformMatrix = [
        m[0] * a + m[2] * b,
        m[1] * a + m[3] * b,
        m[0] * c + m[2] * d,
        m[1] * c + m[3] * d,
        m[0] * e + m[2] * f + m[4],
        m[1] * e + m[3] * f + m[5]
      ];

      ctx._originalTransform(a, b, c, d, e, f);
    };

    ctx.setTransform = function ctxSetTransform(a, b, c, d, e, f) {
      this._transformMatrix = [a, b, c, d, e, f];

      ctx._originalSetTransform(a, b, c, d, e, f);
    };

    ctx.rotate = function ctxRotate(angle) {
      var cosValue = Math.cos(angle);
      var sinValue = Math.sin(angle);

      var m = this._transformMatrix;
      this._transformMatrix = [
        m[0] * cosValue + m[2] * sinValue,
        m[1] * cosValue + m[3] * sinValue,
        m[0] * (-sinValue) + m[2] * cosValue,
        m[1] * (-sinValue) + m[3] * cosValue,
        m[4],
        m[5]
      ];

      this._originalRotate(angle);
    };
  }
}

var CachedCanvases = (function CachedCanvasesClosure() {
  var cache = {};
  return {
    getCanvas: function CachedCanvases_getCanvas(id, width, height,
                                                 trackTransform) {
      var canvasEntry;
      if (id in cache) {
        canvasEntry = cache[id];
        canvasEntry.canvas.width = width;
        canvasEntry.canvas.height = height;
        // reset canvas transform for emulated mozCurrentTransform, if needed
        canvasEntry.context.setTransform(1, 0, 0, 1, 0, 0);
      } else {
        var canvas = createScratchCanvas(width, height);
        var ctx = canvas.getContext('2d');
        if (trackTransform) {
          addContextCurrentTransform(ctx);
        }
        cache[id] = canvasEntry = {canvas: canvas, context: ctx};
      }
      return canvasEntry;
    },
    clear: function () {
      for (var id in cache) {
        var canvasEntry = cache[id];
        // Zeroing the width and height causes Firefox to release graphics
        // resources immediately, which can greatly reduce memory consumption.
        canvasEntry.canvas.width = 0;
        canvasEntry.canvas.height = 0;
        delete cache[id];
      }
    }
  };
})();

function compileType3Glyph(imgData) {
  var POINT_TO_PROCESS_LIMIT = 1000;

  var width = imgData.width, height = imgData.height;
  var i, j, j0, width1 = width + 1;
  var points = new Uint8Array(width1 * (height + 1));
  var POINT_TYPES =
      new Uint8Array([0, 2, 4, 0, 1, 0, 5, 4, 8, 10, 0, 8, 0, 2, 1, 0]);

  // decodes bit-packed mask data
  var lineSize = (width + 7) & ~7, data0 = imgData.data;
  var data = new Uint8Array(lineSize * height), pos = 0, ii;
  for (i = 0, ii = data0.length; i < ii; i++) {
    var mask = 128, elem = data0[i];
    while (mask > 0) {
      data[pos++] = (elem & mask) ? 0 : 255;
      mask >>= 1;
    }
  }

  // finding iteresting points: every point is located between mask pixels,
  // so there will be points of the (width + 1)x(height + 1) grid. Every point
  // will have flags assigned based on neighboring mask pixels:
  //   4 | 8
  //   --P--
  //   2 | 1
  // We are interested only in points with the flags:
  //   - outside corners: 1, 2, 4, 8;
  //   - inside corners: 7, 11, 13, 14;
  //   - and, intersections: 5, 10.
  var count = 0;
  pos = 0;
  if (data[pos] !== 0) {
    points[0] = 1;
    ++count;
  }
  for (j = 1; j < width; j++) {
    if (data[pos] !== data[pos + 1]) {
      points[j] = data[pos] ? 2 : 1;
      ++count;
    }
    pos++;
  }
  if (data[pos] !== 0) {
    points[j] = 2;
    ++count;
  }
  for (i = 1; i < height; i++) {
    pos = i * lineSize;
    j0 = i * width1;
    if (data[pos - lineSize] !== data[pos]) {
      points[j0] = data[pos] ? 1 : 8;
      ++count;
    }
    // 'sum' is the position of the current pixel configuration in the 'TYPES'
    // array (in order 8-1-2-4, so we can use '>>2' to shift the column).
    var sum = (data[pos] ? 4 : 0) + (data[pos - lineSize] ? 8 : 0);
    for (j = 1; j < width; j++) {
      sum = (sum >> 2) + (data[pos + 1] ? 4 : 0) +
            (data[pos - lineSize + 1] ? 8 : 0);
      if (POINT_TYPES[sum]) {
        points[j0 + j] = POINT_TYPES[sum];
        ++count;
      }
      pos++;
    }
    if (data[pos - lineSize] !== data[pos]) {
      points[j0 + j] = data[pos] ? 2 : 4;
      ++count;
    }

    if (count > POINT_TO_PROCESS_LIMIT) {
      return null;
    }
  }

  pos = lineSize * (height - 1);
  j0 = i * width1;
  if (data[pos] !== 0) {
    points[j0] = 8;
    ++count;
  }
  for (j = 1; j < width; j++) {
    if (data[pos] !== data[pos + 1]) {
      points[j0 + j] = data[pos] ? 4 : 8;
      ++count;
    }
    pos++;
  }
  if (data[pos] !== 0) {
    points[j0 + j] = 4;
    ++count;
  }
  if (count > POINT_TO_PROCESS_LIMIT) {
    return null;
  }

  // building outlines
  var steps = new Int32Array([0, width1, -1, 0, -width1, 0, 0, 0, 1]);
  var outlines = [];
  for (i = 0; count && i <= height; i++) {
    var p = i * width1;
    var end = p + width;
    while (p < end && !points[p]) {
      p++;
    }
    if (p === end) {
      continue;
    }
    var coords = [p % width1, i];

    var type = points[p], p0 = p, pp;
    do {
      var step = steps[type];
      do {
        p += step;
      } while (!points[p]);

      pp = points[p];
      if (pp !== 5 && pp !== 10) {
        // set new direction
        type = pp;
        // delete mark
        points[p] = 0;
      } else { // type is 5 or 10, ie, a crossing
        // set new direction
        type = pp & ((0x33 * type) >> 4);
        // set new type for "future hit"
        points[p] &= (type >> 2 | type << 2);
      }

      coords.push(p % width1);
      coords.push((p / width1) | 0);
      --count;
    } while (p0 !== p);
    outlines.push(coords);
    --i;
  }

  var drawOutline = function(c) {
    c.save();
    // the path shall be painted in [0..1]x[0..1] space
    c.scale(1 / width, -1 / height);
    c.translate(0, -height);
    c.beginPath();
    for (var i = 0, ii = outlines.length; i < ii; i++) {
      var o = outlines[i];
      c.moveTo(o[0], o[1]);
      for (var j = 2, jj = o.length; j < jj; j += 2) {
        c.lineTo(o[j], o[j+1]);
      }
    }
    c.fill();
    c.beginPath();
    c.restore();
  };

  return drawOutline;
}

var CanvasExtraState = (function CanvasExtraStateClosure() {
  function CanvasExtraState(old) {
    // Are soft masks and alpha values shapes or opacities?
    this.alphaIsShape = false;
    this.fontSize = 0;
    this.fontSizeScale = 1;
    this.textMatrix = IDENTITY_MATRIX;
    this.textMatrixScale = 1;
    this.fontMatrix = FONT_IDENTITY_MATRIX;
    this.leading = 0;
    // Current point (in user coordinates)
    this.x = 0;
    this.y = 0;
    // Start of text line (in text coordinates)
    this.lineX = 0;
    this.lineY = 0;
    // Character and word spacing
    this.charSpacing = 0;
    this.wordSpacing = 0;
    this.textHScale = 1;
    this.textRenderingMode = TextRenderingMode.FILL;
    this.textRise = 0;
    // Default fore and background colors
    this.fillColor = '#000000';
    this.strokeColor = '#000000';
    // Note: fill alpha applies to all non-stroking operations
    this.fillAlpha = 1;
    this.strokeAlpha = 1;
    this.lineWidth = 1;
    this.activeSMask = null; // nonclonable field (see the save method below)

    this.old = old;
  }

  CanvasExtraState.prototype = {
    clone: function CanvasExtraState_clone() {
      return Object.create(this);
    },
    setCurrentPoint: function CanvasExtraState_setCurrentPoint(x, y) {
      this.x = x;
      this.y = y;
    }
  };
  return CanvasExtraState;
})();

var CanvasGraphics = (function CanvasGraphicsClosure() {
  // Defines the time the executeOperatorList is going to be executing
  // before it stops and shedules a continue of execution.
  var EXECUTION_TIME = 15;
  // Defines the number of steps before checking the execution time
  var EXECUTION_STEPS = 10;

  function CanvasGraphics(canvasCtx, commonObjs, objs, imageLayer) {
    this.ctx = canvasCtx;
    this.current = new CanvasExtraState();
    this.stateStack = [];
    this.pendingClip = null;
    this.pendingEOFill = false;
    this.res = null;
    this.xobjs = null;
    this.commonObjs = commonObjs;
    this.objs = objs;
    this.imageLayer = imageLayer;
    this.groupStack = [];
    this.processingType3 = null;
    // Patterns are painted relative to the initial page/form transform, see pdf
    // spec 8.7.2 NOTE 1.
    this.baseTransform = null;
    this.baseTransformStack = [];
    this.groupLevel = 0;
    this.smaskStack = [];
    this.smaskCounter = 0;
    this.tempSMask = null;
    if (canvasCtx) {
      addContextCurrentTransform(canvasCtx);
    }
  }

  function putBinaryImageData(ctx, imgData) {
    if (typeof ImageData !== 'undefined' && imgData instanceof ImageData) {
      ctx.putImageData(imgData, 0, 0);
      return;
    }

    // Put the image data to the canvas in chunks, rather than putting the
    // whole image at once.  This saves JS memory, because the ImageData object
    // is smaller. It also possibly saves C++ memory within the implementation
    // of putImageData(). (E.g. in Firefox we make two short-lived copies of
    // the data passed to putImageData()). |n| shouldn't be too small, however,
    // because too many putImageData() calls will slow things down.
    //
    // Note: as written, if the last chunk is partial, the putImageData() call
    // will (conceptually) put pixels past the bounds of the canvas.  But
    // that's ok; any such pixels are ignored.

    var height = imgData.height, width = imgData.width;
    var fullChunkHeight = 16;
    var fracChunks = height / fullChunkHeight;
    var fullChunks = Math.floor(fracChunks);
    var totalChunks = Math.ceil(fracChunks);
    var partialChunkHeight = height - fullChunks * fullChunkHeight;

    var chunkImgData = ctx.createImageData(width, fullChunkHeight);
    var srcPos = 0, destPos;
    var src = imgData.data;
    var dest = chunkImgData.data;
    var i, j, thisChunkHeight, elemsInThisChunk;

    // There are multiple forms in which the pixel data can be passed, and
    // imgData.kind tells us which one this is.
    if (imgData.kind === ImageKind.GRAYSCALE_1BPP) {
      // Grayscale, 1 bit per pixel (i.e. black-and-white).
      var srcLength = src.byteLength;
      var dest32 = PDFJS.hasCanvasTypedArrays ? new Uint32Array(dest.buffer) :
        new Uint32ArrayView(dest);
      var dest32DataLength = dest32.length;
      var fullSrcDiff = (width + 7) >> 3;
      var white = 0xFFFFFFFF;
      var black = (PDFJS.isLittleEndian || !PDFJS.hasCanvasTypedArrays) ?
        0xFF000000 : 0x000000FF;
      for (i = 0; i < totalChunks; i++) {
        thisChunkHeight =
          (i < fullChunks) ? fullChunkHeight : partialChunkHeight;
        destPos = 0;
        for (j = 0; j < thisChunkHeight; j++) {
          var srcDiff = srcLength - srcPos;
          var k = 0;
          var kEnd = (srcDiff > fullSrcDiff) ? width : srcDiff * 8 - 7;
          var kEndUnrolled = kEnd & ~7;
          var mask = 0;
          var srcByte = 0;
          for (; k < kEndUnrolled; k += 8) {
            srcByte = src[srcPos++];
            dest32[destPos++] = (srcByte & 128) ? white : black;
            dest32[destPos++] = (srcByte & 64) ? white : black;
            dest32[destPos++] = (srcByte & 32) ? white : black;
            dest32[destPos++] = (srcByte & 16) ? white : black;
            dest32[destPos++] = (srcByte & 8) ? white : black;
            dest32[destPos++] = (srcByte & 4) ? white : black;
            dest32[destPos++] = (srcByte & 2) ? white : black;
            dest32[destPos++] = (srcByte & 1) ? white : black;
          }
          for (; k < kEnd; k++) {
             if (mask === 0) {
               srcByte = src[srcPos++];
               mask = 128;
             }

            dest32[destPos++] = (srcByte & mask) ? white : black;
            mask >>= 1;
          }
        }
        // We ran out of input. Make all remaining pixels transparent.
        while (destPos < dest32DataLength) {
          dest32[destPos++] = 0;
        }

        ctx.putImageData(chunkImgData, 0, i * fullChunkHeight);
      }
    } else if (imgData.kind === ImageKind.RGBA_32BPP) {
      // RGBA, 32-bits per pixel.

      j = 0;
      elemsInThisChunk = width * fullChunkHeight * 4;
      for (i = 0; i < fullChunks; i++) {
        dest.set(src.subarray(srcPos, srcPos + elemsInThisChunk));
        srcPos += elemsInThisChunk;

        ctx.putImageData(chunkImgData, 0, j);
        j += fullChunkHeight;
      }
      if (i < totalChunks) {
        elemsInThisChunk = width * partialChunkHeight * 4;
        dest.set(src.subarray(srcPos, srcPos + elemsInThisChunk));
        ctx.putImageData(chunkImgData, 0, j);
      }

    } else if (imgData.kind === ImageKind.RGB_24BPP) {
      // RGB, 24-bits per pixel.
      thisChunkHeight = fullChunkHeight;
      elemsInThisChunk = width * thisChunkHeight;
      for (i = 0; i < totalChunks; i++) {
        if (i >= fullChunks) {
          thisChunkHeight =partialChunkHeight;
          elemsInThisChunk = width * thisChunkHeight;
        }

        destPos = 0;
        for (j = elemsInThisChunk; j--;) {
          dest[destPos++] = src[srcPos++];
          dest[destPos++] = src[srcPos++];
          dest[destPos++] = src[srcPos++];
          dest[destPos++] = 255;
        }
        ctx.putImageData(chunkImgData, 0, i * fullChunkHeight);
      }
    } else {
      error('bad image kind: ' + imgData.kind);
    }
  }

  function putBinaryImageMask(ctx, imgData) {
    var height = imgData.height, width = imgData.width;
    var fullChunkHeight = 16;
    var fracChunks = height / fullChunkHeight;
    var fullChunks = Math.floor(fracChunks);
    var totalChunks = Math.ceil(fracChunks);
    var partialChunkHeight = height - fullChunks * fullChunkHeight;

    var chunkImgData = ctx.createImageData(width, fullChunkHeight);
    var srcPos = 0;
    var src = imgData.data;
    var dest = chunkImgData.data;

    for (var i = 0; i < totalChunks; i++) {
      var thisChunkHeight =
        (i < fullChunks) ? fullChunkHeight : partialChunkHeight;

      // Expand the mask so it can be used by the canvas.  Any required
      // inversion has already been handled.
      var destPos = 3; // alpha component offset
      for (var j = 0; j < thisChunkHeight; j++) {
        var mask = 0;
        for (var k = 0; k < width; k++) {
          if (!mask) {
            var elem = src[srcPos++];
            mask = 128;
          }
          dest[destPos] = (elem & mask) ? 0 : 255;
          destPos += 4;
          mask >>= 1;
        }
      }
      ctx.putImageData(chunkImgData, 0, i * fullChunkHeight);
    }
  }

  function copyCtxState(sourceCtx, destCtx) {
    var properties = ['strokeStyle', 'fillStyle', 'fillRule', 'globalAlpha',
                      'lineWidth', 'lineCap', 'lineJoin', 'miterLimit',
                      'globalCompositeOperation', 'font'];
    for (var i = 0, ii = properties.length; i < ii; i++) {
      var property = properties[i];
      if (property in sourceCtx) {
        destCtx[property] = sourceCtx[property];
      }
    }
    if ('setLineDash' in sourceCtx) {
      destCtx.setLineDash(sourceCtx.getLineDash());
      destCtx.lineDashOffset =  sourceCtx.lineDashOffset;
    } else if ('mozDash' in sourceCtx) {
      destCtx.mozDash = sourceCtx.mozDash;
      destCtx.mozDashOffset = sourceCtx.mozDashOffset;
    }
  }

  function composeSMaskBackdrop(bytes, r0, g0, b0) {
    var length = bytes.length;
    for (var i = 3; i < length; i += 4) {
      var alpha = bytes[i];
      if (alpha === 0) {
        bytes[i - 3] = r0;
        bytes[i - 2] = g0;
        bytes[i - 1] = b0;
      } else if (alpha < 255) {
        var alpha_ = 255 - alpha;
        bytes[i - 3] = (bytes[i - 3] * alpha + r0 * alpha_) >> 8;
        bytes[i - 2] = (bytes[i - 2] * alpha + g0 * alpha_) >> 8;
        bytes[i - 1] = (bytes[i - 1] * alpha + b0 * alpha_) >> 8;
      }
    }
  }

  function composeSMaskAlpha(maskData, layerData) {
    var length = maskData.length;
    var scale = 1 / 255;
    for (var i = 3; i < length; i += 4) {
      var alpha = maskData[i];
      layerData[i] = (layerData[i] * alpha * scale) | 0;
    }
  }

  function composeSMaskLuminosity(maskData, layerData) {
    var length = maskData.length;
    for (var i = 3; i < length; i += 4) {
      var y = ((maskData[i - 3] * 77) +     // * 0.3 / 255 * 0x10000
               (maskData[i - 2] * 152) +    // * 0.59 ....
               (maskData[i - 1] * 28)) | 0; // * 0.11 ....
      layerData[i] = (layerData[i] * y) >> 16;
    }
  }

  function genericComposeSMask(maskCtx, layerCtx, width, height,
                               subtype, backdrop) {
    var hasBackdrop = !!backdrop;
    var r0 = hasBackdrop ? backdrop[0] : 0;
    var g0 = hasBackdrop ? backdrop[1] : 0;
    var b0 = hasBackdrop ? backdrop[2] : 0;

    var composeFn;
    if (subtype === 'Luminosity') {
      composeFn = composeSMaskLuminosity;
    } else {
      composeFn = composeSMaskAlpha;
    }

    // processing image in chunks to save memory
    var PIXELS_TO_PROCESS = 65536;
    var chunkSize = Math.min(height, Math.ceil(PIXELS_TO_PROCESS / width));
    for (var row = 0; row < height; row += chunkSize) {
      var chunkHeight = Math.min(chunkSize, height - row);
      var maskData = maskCtx.getImageData(0, row, width, chunkHeight);
      var layerData = layerCtx.getImageData(0, row, width, chunkHeight);

      if (hasBackdrop) {
        composeSMaskBackdrop(maskData.data, r0, g0, b0);
      }
      composeFn(maskData.data, layerData.data);

      maskCtx.putImageData(layerData, 0, row);
    }
  }

  function composeSMask(ctx, smask, layerCtx) {
    var mask = smask.canvas;
    var maskCtx = smask.context;

    ctx.setTransform(smask.scaleX, 0, 0, smask.scaleY,
                     smask.offsetX, smask.offsetY);

    var backdrop = smask.backdrop || null;
    if (WebGLUtils.isEnabled) {
      var composed = WebGLUtils.composeSMask(layerCtx.canvas, mask,
        {subtype: smask.subtype, backdrop: backdrop});
      ctx.setTransform(1, 0, 0, 1, 0, 0);
      ctx.drawImage(composed, smask.offsetX, smask.offsetY);
      return;
    }
    genericComposeSMask(maskCtx, layerCtx, mask.width, mask.height,
                        smask.subtype, backdrop);
    ctx.drawImage(mask, 0, 0);
  }

  var LINE_CAP_STYLES = ['butt', 'round', 'square'];
  var LINE_JOIN_STYLES = ['miter', 'round', 'bevel'];
  var NORMAL_CLIP = {};
  var EO_CLIP = {};

  CanvasGraphics.prototype = {

    beginDrawing: function CanvasGraphics_beginDrawing(viewport, transparency) {
      // For pdfs that use blend modes we have to clear the canvas else certain
      // blend modes can look wrong since we'd be blending with a white
      // backdrop. The problem with a transparent backdrop though is we then
      // don't get sub pixel anti aliasing on text, so we fill with white if
      // we can.
      var width = this.ctx.canvas.width;
      var height = this.ctx.canvas.height;
      if (transparency) {
        this.ctx.clearRect(0, 0, width, height);
      } else {
        this.ctx.mozOpaque = true;
        this.ctx.save();
        this.ctx.fillStyle = 'rgb(255, 255, 255)';
        this.ctx.fillRect(0, 0, width, height);
        this.ctx.restore();
      }

      var transform = viewport.transform;

      this.ctx.save();
      this.ctx.transform.apply(this.ctx, transform);

      this.baseTransform = this.ctx.mozCurrentTransform.slice();

      if (this.imageLayer) {
        this.imageLayer.beginLayout();
      }
    },

    executeOperatorList: function CanvasGraphics_executeOperatorList(
                                    operatorList,
                                    executionStartIdx, continueCallback,
                                    stepper) {
      var argsArray = operatorList.argsArray;
      var fnArray = operatorList.fnArray;
      var i = executionStartIdx || 0;
      var argsArrayLen = argsArray.length;

      // Sometimes the OperatorList to execute is empty.
      if (argsArrayLen === i) {
        return i;
      }

      var chunkOperations = (argsArrayLen - i > EXECUTION_STEPS &&
                             typeof continueCallback === 'function');
      var endTime = chunkOperations ? Date.now() + EXECUTION_TIME : 0;
      var steps = 0;

      var commonObjs = this.commonObjs;
      var objs = this.objs;
      var fnId;

      while (true) {
        if (stepper !== undefined && i === stepper.nextBreakPoint) {
          stepper.breakIt(i, continueCallback);
          return i;
        }

        fnId = fnArray[i];

        if (fnId !== OPS.dependency) {
          this[fnId].apply(this, argsArray[i]);
        } else {
          var deps = argsArray[i];
          for (var n = 0, nn = deps.length; n < nn; n++) {
            var depObjId = deps[n];
            var common = depObjId[0] === 'g' && depObjId[1] === '_';
            var objsPool = common ? commonObjs : objs;

            // If the promise isn't resolved yet, add the continueCallback
            // to the promise and bail out.
            if (!objsPool.isResolved(depObjId)) {
              objsPool.get(depObjId, continueCallback);
              return i;
            }
          }
        }

        i++;

        // If the entire operatorList was executed, stop as were done.
        if (i === argsArrayLen) {
          return i;
        }

        // If the execution took longer then a certain amount of time and
        // `continueCallback` is specified, interrupt the execution.
        if (chunkOperations && ++steps > EXECUTION_STEPS) {
          if (Date.now() > endTime) {
            continueCallback();
            return i;
          }
          steps = 0;
        }

        // If the operatorList isn't executed completely yet OR the execution
        // time was short enough, do another execution round.
      }
    },

    endDrawing: function CanvasGraphics_endDrawing() {
      this.ctx.restore();
      CachedCanvases.clear();
      WebGLUtils.clear();

      if (this.imageLayer) {
        this.imageLayer.endLayout();
      }
    },

    // Graphics state
    setLineWidth: function CanvasGraphics_setLineWidth(width) {
      this.current.lineWidth = width;
      this.ctx.lineWidth = width;
    },
    setLineCap: function CanvasGraphics_setLineCap(style) {
      this.ctx.lineCap = LINE_CAP_STYLES[style];
    },
    setLineJoin: function CanvasGraphics_setLineJoin(style) {
      this.ctx.lineJoin = LINE_JOIN_STYLES[style];
    },
    setMiterLimit: function CanvasGraphics_setMiterLimit(limit) {
      this.ctx.miterLimit = limit;
    },
    setDash: function CanvasGraphics_setDash(dashArray, dashPhase) {
      var ctx = this.ctx;
      if ('setLineDash' in ctx) {
        ctx.setLineDash(dashArray);
        ctx.lineDashOffset = dashPhase;
      } else {
        ctx.mozDash = dashArray;
        ctx.mozDashOffset = dashPhase;
      }
    },
    setRenderingIntent: function CanvasGraphics_setRenderingIntent(intent) {
      // Maybe if we one day fully support color spaces this will be important
      // for now we can ignore.
      // TODO set rendering intent?
    },
    setFlatness: function CanvasGraphics_setFlatness(flatness) {
      // There's no way to control this with canvas, but we can safely ignore.
      // TODO set flatness?
    },
    setGState: function CanvasGraphics_setGState(states) {
      for (var i = 0, ii = states.length; i < ii; i++) {
        var state = states[i];
        var key = state[0];
        var value = state[1];

        switch (key) {
          case 'LW':
            this.setLineWidth(value);
            break;
          case 'LC':
            this.setLineCap(value);
            break;
          case 'LJ':
            this.setLineJoin(value);
            break;
          case 'ML':
            this.setMiterLimit(value);
            break;
          case 'D':
            this.setDash(value[0], value[1]);
            break;
          case 'RI':
            this.setRenderingIntent(value);
            break;
          case 'FL':
            this.setFlatness(value);
            break;
          case 'Font':
            this.setFont(value[0], value[1]);
            break;
          case 'CA':
            this.current.strokeAlpha = state[1];
            break;
          case 'ca':
            this.current.fillAlpha = state[1];
            this.ctx.globalAlpha = state[1];
            break;
          case 'BM':
            if (value && value.name && (value.name !== 'Normal')) {
              var mode = value.name.replace(/([A-Z])/g,
                function(c) {
                  return '-' + c.toLowerCase();
                }
              ).substring(1);
              this.ctx.globalCompositeOperation = mode;
              if (this.ctx.globalCompositeOperation !== mode) {
                warn('globalCompositeOperation "' + mode +
                     '" is not supported');
              }
            } else {
              this.ctx.globalCompositeOperation = 'source-over';
            }
            break;
          case 'SMask':
            if (this.current.activeSMask) {
              this.endSMaskGroup();
            }
            this.current.activeSMask = value ? this.tempSMask : null;
            if (this.current.activeSMask) {
              this.beginSMaskGroup();
            }
            this.tempSMask = null;
            break;
        }
      }
    },
    beginSMaskGroup: function CanvasGraphics_beginSMaskGroup() {

      var activeSMask = this.current.activeSMask;
      var drawnWidth = activeSMask.canvas.width;
      var drawnHeight = activeSMask.canvas.height;
      var cacheId = 'smaskGroupAt' + this.groupLevel;
      var scratchCanvas = CachedCanvases.getCanvas(
        cacheId, drawnWidth, drawnHeight, true);

      var currentCtx = this.ctx;
      var currentTransform = currentCtx.mozCurrentTransform;
      this.ctx.save();

      var groupCtx = scratchCanvas.context;
      groupCtx.scale(1 / activeSMask.scaleX, 1 / activeSMask.scaleY);
      groupCtx.translate(-activeSMask.offsetX, -activeSMask.offsetY);
      groupCtx.transform.apply(groupCtx, currentTransform);

      copyCtxState(currentCtx, groupCtx);
      this.ctx = groupCtx;
      this.setGState([
        ['BM', 'Normal'],
        ['ca', 1],
        ['CA', 1]
      ]);
      this.groupStack.push(currentCtx);
      this.groupLevel++;
    },
    endSMaskGroup: function CanvasGraphics_endSMaskGroup() {
      var groupCtx = this.ctx;
      this.groupLevel--;
      this.ctx = this.groupStack.pop();

      composeSMask(this.ctx, this.current.activeSMask, groupCtx);
      this.ctx.restore();
    },
    save: function CanvasGraphics_save() {
      this.ctx.save();
      var old = this.current;
      this.stateStack.push(old);
      this.current = old.clone();
      this.current.activeSMask = null;
    },
    restore: function CanvasGraphics_restore() {
      if (this.stateStack.length !== 0) {
        if (this.current.activeSMask !== null) {
          this.endSMaskGroup();
        }

        this.current = this.stateStack.pop();
        this.ctx.restore();
      }
    },
    transform: function CanvasGraphics_transform(a, b, c, d, e, f) {
      this.ctx.transform(a, b, c, d, e, f);
    },

    // Path
    constructPath: function CanvasGraphics_constructPath(ops, args) {
      var ctx = this.ctx;
      var current = this.current;
      var x = current.x, y = current.y;
      for (var i = 0, j = 0, ii = ops.length; i < ii; i++) {
        switch (ops[i] | 0) {
          case OPS.moveTo:
            x = args[j++];
            y = args[j++];
            ctx.moveTo(x, y);
            break;
          case OPS.lineTo:
            x = args[j++];
            y = args[j++];
            ctx.lineTo(x, y);
            break;
          case OPS.curveTo:
            x = args[j + 4];
            y = args[j + 5];
            ctx.bezierCurveTo(args[j], args[j + 1], args[j + 2], args[j + 3],
                              x, y);
            j += 6;
            break;
          case OPS.curveTo2:
            ctx.bezierCurveTo(x, y, args[j], args[j + 1],
                              args[j + 2], args[j + 3]);
            x = args[j + 2];
            y = args[j + 3];
            j += 4;
            break;
          case OPS.curveTo3:
            x = args[j + 2];
            y = args[j + 3];
            ctx.bezierCurveTo(args[j], args[j + 1], x, y, x, y);
            j += 4;
            break;
          case OPS.closePath:
            ctx.closePath();
            break;
        }
      }
      current.setCurrentPoint(x, y);
    },
    closePath: function CanvasGraphics_closePath() {
      this.ctx.closePath();
    },
    rectangle: function CanvasGraphics_rectangle(x, y, width, height) {
      if (width === 0) {
        width = this.getSinglePixelWidth();
      }
      if (height === 0) {
        height = this.getSinglePixelWidth();
      }

      this.ctx.rect(x, y, width, height);
    },
    stroke: function CanvasGraphics_stroke(consumePath) {
      consumePath = typeof consumePath !== 'undefined' ? consumePath : true;
      var ctx = this.ctx;
      var strokeColor = this.current.strokeColor;
      if (this.current.lineWidth === 0) {
        ctx.lineWidth = this.getSinglePixelWidth();
      }
      // For stroke we want to temporarily change the global alpha to the
      // stroking alpha.
      ctx.globalAlpha = this.current.strokeAlpha;
      if (strokeColor && strokeColor.hasOwnProperty('type') &&
          strokeColor.type === 'Pattern') {
        // for patterns, we transform to pattern space, calculate
        // the pattern, call stroke, and restore to user space
        ctx.save();
        ctx.strokeStyle = strokeColor.getPattern(ctx, this);
        ctx.stroke();
        ctx.restore();
      } else {
        ctx.stroke();
      }
      if (consumePath) {
        this.consumePath();
      }
      // Restore the global alpha to the fill alpha
      ctx.globalAlpha = this.current.fillAlpha;
    },
    closeStroke: function CanvasGraphics_closeStroke() {
      this.closePath();
      this.stroke();
    },
    fill: function CanvasGraphics_fill(consumePath) {
      consumePath = typeof consumePath !== 'undefined' ? consumePath : true;
      var ctx = this.ctx;
      var fillColor = this.current.fillColor;
      var needRestore = false;

      if (fillColor && fillColor.hasOwnProperty('type') &&
          fillColor.type === 'Pattern') {
        ctx.save();
        ctx.fillStyle = fillColor.getPattern(ctx, this);
        needRestore = true;
      }

      if (this.pendingEOFill) {
        if (ctx.mozFillRule !== undefined) {
          ctx.mozFillRule = 'evenodd';
          ctx.fill();
          ctx.mozFillRule = 'nonzero';
        } else {
          try {
            ctx.fill('evenodd');
          } catch (ex) {
            // shouldn't really happen, but browsers might think differently
            ctx.fill();
          }
        }
        this.pendingEOFill = false;
      } else {
        ctx.fill();
      }

      if (needRestore) {
        ctx.restore();
      }
      if (consumePath) {
        this.consumePath();
      }
    },
    eoFill: function CanvasGraphics_eoFill() {
      this.pendingEOFill = true;
      this.fill();
    },
    fillStroke: function CanvasGraphics_fillStroke() {
      this.fill(false);
      this.stroke(false);

      this.consumePath();
    },
    eoFillStroke: function CanvasGraphics_eoFillStroke() {
      this.pendingEOFill = true;
      this.fillStroke();
    },
    closeFillStroke: function CanvasGraphics_closeFillStroke() {
      this.closePath();
      this.fillStroke();
    },
    closeEOFillStroke: function CanvasGraphics_closeEOFillStroke() {
      this.pendingEOFill = true;
      this.closePath();
      this.fillStroke();
    },
    endPath: function CanvasGraphics_endPath() {
      this.consumePath();
    },

    // Clipping
    clip: function CanvasGraphics_clip() {
      this.pendingClip = NORMAL_CLIP;
    },
    eoClip: function CanvasGraphics_eoClip() {
      this.pendingClip = EO_CLIP;
    },

    // Text
    beginText: function CanvasGraphics_beginText() {
      this.current.textMatrix = IDENTITY_MATRIX;
      this.current.textMatrixScale = 1;
      this.current.x = this.current.lineX = 0;
      this.current.y = this.current.lineY = 0;
    },
    endText: function CanvasGraphics_endText() {
      var paths = this.pendingTextPaths;
      var ctx = this.ctx;
      if (paths === undefined) {
        ctx.beginPath();
        return;
      }

      ctx.save();
      ctx.beginPath();
      for (var i = 0; i < paths.length; i++) {
        var path = paths[i];
        ctx.setTransform.apply(ctx, path.transform);
        ctx.translate(path.x, path.y);
        path.addToPath(ctx, path.fontSize);
      }
      ctx.restore();
      ctx.clip();
      ctx.beginPath();
      delete this.pendingTextPaths;
    },
    setCharSpacing: function CanvasGraphics_setCharSpacing(spacing) {
      this.current.charSpacing = spacing;
    },
    setWordSpacing: function CanvasGraphics_setWordSpacing(spacing) {
      this.current.wordSpacing = spacing;
    },
    setHScale: function CanvasGraphics_setHScale(scale) {
      this.current.textHScale = scale / 100;
    },
    setLeading: function CanvasGraphics_setLeading(leading) {
      this.current.leading = -leading;
    },
    setFont: function CanvasGraphics_setFont(fontRefName, size) {
      var fontObj = this.commonObjs.get(fontRefName);
      var current = this.current;

      if (!fontObj) {
        error('Can\'t find font for ' + fontRefName);
      }

      current.fontMatrix = (fontObj.fontMatrix ?
                            fontObj.fontMatrix : FONT_IDENTITY_MATRIX);

      // A valid matrix needs all main diagonal elements to be non-zero
      // This also ensures we bypass FF bugzilla bug #719844.
      if (current.fontMatrix[0] === 0 ||
          current.fontMatrix[3] === 0) {
        warn('Invalid font matrix for font ' + fontRefName);
      }

      // The spec for Tf (setFont) says that 'size' specifies the font 'scale',
      // and in some docs this can be negative (inverted x-y axes).
      if (size < 0) {
        size = -size;
        current.fontDirection = -1;
      } else {
        current.fontDirection = 1;
      }

      this.current.font = fontObj;
      this.current.fontSize = size;

      if (fontObj.isType3Font) {
        return; // we don't need ctx.font for Type3 fonts
      }

      var name = fontObj.loadedName || 'sans-serif';
      var bold = fontObj.black ? (fontObj.bold ? 'bolder' : 'bold') :
                                 (fontObj.bold ? 'bold' : 'normal');

      var italic = fontObj.italic ? 'italic' : 'normal';
      var typeface = '"' + name + '", ' + fontObj.fallbackName;

      // Some font backends cannot handle fonts below certain size.
      // Keeping the font at minimal size and using the fontSizeScale to change
      // the current transformation matrix before the fillText/strokeText.
      // See https://bugzilla.mozilla.org/show_bug.cgi?id=726227
      var browserFontSize = size >= MIN_FONT_SIZE ? size : MIN_FONT_SIZE;
      this.current.fontSizeScale = browserFontSize != MIN_FONT_SIZE ? 1.0 :
                                   size / MIN_FONT_SIZE;

      var rule = italic + ' ' + bold + ' ' + browserFontSize + 'px ' + typeface;
      this.ctx.font = rule;
    },
    setTextRenderingMode: function CanvasGraphics_setTextRenderingMode(mode) {
      this.current.textRenderingMode = mode;
    },
    setTextRise: function CanvasGraphics_setTextRise(rise) {
      this.current.textRise = rise;
    },
    moveText: function CanvasGraphics_moveText(x, y) {
      this.current.x = this.current.lineX += x;
      this.current.y = this.current.lineY += y;
    },
    setLeadingMoveText: function CanvasGraphics_setLeadingMoveText(x, y) {
      this.setLeading(-y);
      this.moveText(x, y);
    },
    setTextMatrix: function CanvasGraphics_setTextMatrix(a, b, c, d, e, f) {
      this.current.textMatrix = [a, b, c, d, e, f];
      this.current.textMatrixScale = Math.sqrt(a * a + b * b);

      this.current.x = this.current.lineX = 0;
      this.current.y = this.current.lineY = 0;
    },
    nextLine: function CanvasGraphics_nextLine() {
      this.moveText(0, this.current.leading);
    },

    paintChar: function CanvasGraphics_paintChar(character, x, y) {
      var ctx = this.ctx;
      var current = this.current;
      var font = current.font;
      var textRenderingMode = current.textRenderingMode;
      var fontSize = current.fontSize / current.fontSizeScale;
      var fillStrokeMode = textRenderingMode &
        TextRenderingMode.FILL_STROKE_MASK;
      var isAddToPathSet = !!(textRenderingMode &
        TextRenderingMode.ADD_TO_PATH_FLAG);

      var addToPath;
      if (font.disableFontFace || isAddToPathSet) {
        addToPath = font.getPathGenerator(this.commonObjs, character);
      }

      if (font.disableFontFace) {
        ctx.save();
        ctx.translate(x, y);
        ctx.beginPath();
        addToPath(ctx, fontSize);
        if (fillStrokeMode === TextRenderingMode.FILL ||
            fillStrokeMode === TextRenderingMode.FILL_STROKE) {
          ctx.fill();
        }
        if (fillStrokeMode === TextRenderingMode.STROKE ||
            fillStrokeMode === TextRenderingMode.FILL_STROKE) {
          ctx.stroke();
        }
        ctx.restore();
      } else {
        if (fillStrokeMode === TextRenderingMode.FILL ||
            fillStrokeMode === TextRenderingMode.FILL_STROKE) {
          ctx.fillText(character, x, y);
        }
        if (fillStrokeMode === TextRenderingMode.STROKE ||
            fillStrokeMode === TextRenderingMode.FILL_STROKE) {
          ctx.strokeText(character, x, y);
        }
      }

      if (isAddToPathSet) {
        var paths = this.pendingTextPaths || (this.pendingTextPaths = []);
        paths.push({
          transform: ctx.mozCurrentTransform,
          x: x,
          y: y,
          fontSize: fontSize,
          addToPath: addToPath
        });
      }
    },

    get isFontSubpixelAAEnabled() {
      // Checks if anti-aliasing is enabled when scaled text is painted.
      // On Windows GDI scaled fonts looks bad.
      var ctx = document.createElement('canvas').getContext('2d');
      ctx.scale(1.5, 1);
      ctx.fillText('I', 0, 10);
      var data = ctx.getImageData(0, 0, 10, 10).data;
      var enabled = false;
      for (var i = 3; i < data.length; i += 4) {
        if (data[i] > 0 && data[i] < 255) {
          enabled = true;
          break;
        }
      }
      return shadow(this, 'isFontSubpixelAAEnabled', enabled);
    },

    showText: function CanvasGraphics_showText(glyphs) {
      var current = this.current;
      var font = current.font;
      if (font.isType3Font) {
        return this.showType3Text(glyphs);
      }

      var fontSize = current.fontSize;
      if (fontSize === 0) {
        return;
      }

      var ctx = this.ctx;
      var fontSizeScale = current.fontSizeScale;
      var charSpacing = current.charSpacing;
      var wordSpacing = current.wordSpacing;
      var fontDirection = current.fontDirection;
      var textHScale = current.textHScale * fontDirection;
      var glyphsLength = glyphs.length;
      var vertical = font.vertical;
      var defaultVMetrics = font.defaultVMetrics;
      var widthAdvanceScale = fontSize * current.fontMatrix[0];

      var simpleFillText =
        current.textRenderingMode === TextRenderingMode.FILL &&
        !font.disableFontFace;

      ctx.save();
      ctx.transform.apply(ctx, current.textMatrix);
      ctx.translate(current.x, current.y + current.textRise);

      if (fontDirection > 0) {
        ctx.scale(textHScale, -1);
      } else {
        ctx.scale(textHScale, 1);
      }

      var lineWidth = current.lineWidth;
      var scale = current.textMatrixScale;
      if (scale === 0 || lineWidth === 0) {
        lineWidth = this.getSinglePixelWidth();
      } else {
        lineWidth /= scale;
      }

      if (fontSizeScale != 1.0) {
        ctx.scale(fontSizeScale, fontSizeScale);
        lineWidth /= fontSizeScale;
      }

      ctx.lineWidth = lineWidth;

      var x = 0, i;
      for (i = 0; i < glyphsLength; ++i) {
        var glyph = glyphs[i];
        if (glyph === null) {
          // word break
          x += fontDirection * wordSpacing;
          continue;
        } else if (isNum(glyph)) {
          x += -glyph * fontSize * 0.001;
          continue;
        }

        var restoreNeeded = false;
        var character = glyph.fontChar;
        var accent = glyph.accent;
        var scaledX, scaledY, scaledAccentX, scaledAccentY;
        var width = glyph.width;
        if (vertical) {
          var vmetric, vx, vy;
          vmetric = glyph.vmetric || defaultVMetrics;
          vx = glyph.vmetric ? vmetric[1] : width * 0.5;
          vx = -vx * widthAdvanceScale;
          vy = vmetric[2] * widthAdvanceScale;

          width = vmetric ? -vmetric[0] : width;
          scaledX = vx / fontSizeScale;
          scaledY = (x + vy) / fontSizeScale;
        } else {
          scaledX = x / fontSizeScale;
          scaledY = 0;
        }

        if (font.remeasure && width > 0 && this.isFontSubpixelAAEnabled) {
          // some standard fonts may not have the exact width, trying to
          // rescale per character
          var measuredWidth = ctx.measureText(character).width * 1000 /
            fontSize * fontSizeScale;
          var characterScaleX = width / measuredWidth;
          restoreNeeded = true;
          ctx.save();
          ctx.scale(characterScaleX, 1);
          scaledX /= characterScaleX;
        }

        if (simpleFillText && !accent) {
          // common case
          ctx.fillText(character, scaledX, scaledY);
        } else {
          this.paintChar(character, scaledX, scaledY);
          if (accent) {
            scaledAccentX = scaledX + accent.offset.x / fontSizeScale;
            scaledAccentY = scaledY - accent.offset.y / fontSizeScale;
            this.paintChar(accent.fontChar, scaledAccentX, scaledAccentY);
          }
        }

        var charWidth = width * widthAdvanceScale + charSpacing * fontDirection;
        x += charWidth;

        if (restoreNeeded) {
          ctx.restore();
        }
      }
      if (vertical) {
        current.y -= x * textHScale;
      } else {
        current.x += x * textHScale;
      }
      ctx.restore();
    },

    showType3Text: function CanvasGraphics_showType3Text(glyphs) {
      // Type3 fonts - each glyph is a "mini-PDF"
      var ctx = this.ctx;
      var current = this.current;
      var font = current.font;
      var fontSize = current.fontSize;
      var fontDirection = current.fontDirection;
      var charSpacing = current.charSpacing;
      var wordSpacing = current.wordSpacing;
      var textHScale = current.textHScale * fontDirection;
      var fontMatrix = current.fontMatrix || FONT_IDENTITY_MATRIX;
      var glyphsLength = glyphs.length;
      var i, glyph, width;

      if (fontSize === 0) {
        return;
      }

      ctx.save();
      ctx.transform.apply(ctx, current.textMatrix);
      ctx.translate(current.x, current.y);

      ctx.scale(textHScale, 1);

      for (i = 0; i < glyphsLength; ++i) {
        glyph = glyphs[i];
        if (glyph === null) {
          // word break
          this.ctx.translate(wordSpacing, 0);
          current.x += wordSpacing * textHScale;
          continue;
        } else if (isNum(glyph)) {
          var spacingLength = -glyph * 0.001 * fontSize;
          this.ctx.translate(spacingLength, 0);
          current.x += spacingLength * textHScale;
          continue;
        }

        this.processingType3 = glyph;
        this.save();
        ctx.scale(fontSize, fontSize);
        ctx.transform.apply(ctx, fontMatrix);
        var operatorList = font.charProcOperatorList[glyph.operatorListId];
        this.executeOperatorList(operatorList);
        this.restore();

        var transformed = Util.applyTransform([glyph.width, 0], fontMatrix);
        width = ((transformed[0] * fontSize + charSpacing) * fontDirection);

        ctx.translate(width, 0);
        current.x += width * textHScale;
      }
      ctx.restore();
      this.processingType3 = null;
    },

    // Type3 fonts
    setCharWidth: function CanvasGraphics_setCharWidth(xWidth, yWidth) {
      // We can safely ignore this since the width should be the same
      // as the width in the Widths array.
    },
    setCharWidthAndBounds: function CanvasGraphics_setCharWidthAndBounds(xWidth,
                                                                        yWidth,
                                                                        llx,
                                                                        lly,
                                                                        urx,
                                                                        ury) {
      // TODO According to the spec we're also suppose to ignore any operators
      // that set color or include images while processing this type3 font.
      this.rectangle(llx, lly, urx - llx, ury - lly);
      this.clip();
      this.endPath();
    },

    // Color
    getColorN_Pattern: function CanvasGraphics_getColorN_Pattern(IR) {
      var pattern;
      if (IR[0] === 'TilingPattern') {
        var color = IR[1];
        pattern = new TilingPattern(IR, color, this.ctx, this.objs,
                                    this.commonObjs, this.baseTransform);
      } else {
        pattern = getShadingPatternFromIR(IR);
      }
      return pattern;
    },
    setStrokeColorN: function CanvasGraphics_setStrokeColorN(/*...*/) {
      this.current.strokeColor = this.getColorN_Pattern(arguments);
    },
    setFillColorN: function CanvasGraphics_setFillColorN(/*...*/) {
      this.current.fillColor = this.getColorN_Pattern(arguments);
    },
    setStrokeRGBColor: function CanvasGraphics_setStrokeRGBColor(r, g, b) {
      var color = Util.makeCssRgb(arguments);
      this.ctx.strokeStyle = color;
      this.current.strokeColor = color;
    },
    setFillRGBColor: function CanvasGraphics_setFillRGBColor(r, g, b) {
      var color = Util.makeCssRgb(arguments);
      this.ctx.fillStyle = color;
      this.current.fillColor = color;
    },

    shadingFill: function CanvasGraphics_shadingFill(patternIR) {
      var ctx = this.ctx;

      this.save();
      var pattern = getShadingPatternFromIR(patternIR);
      ctx.fillStyle = pattern.getPattern(ctx, this, true);

      var inv = ctx.mozCurrentTransformInverse;
      if (inv) {
        var canvas = ctx.canvas;
        var width = canvas.width;
        var height = canvas.height;

        var bl = Util.applyTransform([0, 0], inv);
        var br = Util.applyTransform([0, height], inv);
        var ul = Util.applyTransform([width, 0], inv);
        var ur = Util.applyTransform([width, height], inv);

        var x0 = Math.min(bl[0], br[0], ul[0], ur[0]);
        var y0 = Math.min(bl[1], br[1], ul[1], ur[1]);
        var x1 = Math.max(bl[0], br[0], ul[0], ur[0]);
        var y1 = Math.max(bl[1], br[1], ul[1], ur[1]);

        this.ctx.fillRect(x0, y0, x1 - x0, y1 - y0);
      } else {
        // HACK to draw the gradient onto an infinite rectangle.
        // PDF gradients are drawn across the entire image while
        // Canvas only allows gradients to be drawn in a rectangle
        // The following bug should allow us to remove this.
        // https://bugzilla.mozilla.org/show_bug.cgi?id=664884

        this.ctx.fillRect(-1e10, -1e10, 2e10, 2e10);
      }

      this.restore();
    },

    // Images
    beginInlineImage: function CanvasGraphics_beginInlineImage() {
      error('Should not call beginInlineImage');
    },
    beginImageData: function CanvasGraphics_beginImageData() {
      error('Should not call beginImageData');
    },

    paintFormXObjectBegin: function CanvasGraphics_paintFormXObjectBegin(matrix,
                                                                        bbox) {
      this.save();
      this.baseTransformStack.push(this.baseTransform);

      if (isArray(matrix) && 6 === matrix.length) {
        this.transform.apply(this, matrix);
      }

      this.baseTransform = this.ctx.mozCurrentTransform;

      if (isArray(bbox) && 4 === bbox.length) {
        var width = bbox[2] - bbox[0];
        var height = bbox[3] - bbox[1];
        this.rectangle(bbox[0], bbox[1], width, height);
        this.clip();
        this.endPath();
      }
    },

    paintFormXObjectEnd: function CanvasGraphics_paintFormXObjectEnd() {
      this.restore();
      this.baseTransform = this.baseTransformStack.pop();
    },

    beginGroup: function CanvasGraphics_beginGroup(group) {
      this.save();
      var currentCtx = this.ctx;
      // TODO non-isolated groups - according to Rik at adobe non-isolated
      // group results aren't usually that different and they even have tools
      // that ignore this setting. Notes from Rik on implmenting:
      // - When you encounter an transparency group, create a new canvas with
      // the dimensions of the bbox
      // - copy the content from the previous canvas to the new canvas
      // - draw as usual
      // - remove the backdrop alpha:
      // alphaNew = 1 - (1 - alpha)/(1 - alphaBackdrop) with 'alpha' the alpha
      // value of your transparency group and 'alphaBackdrop' the alpha of the
      // backdrop
      // - remove background color:
      // colorNew = color - alphaNew *colorBackdrop /(1 - alphaNew)
      if (!group.isolated) {
        info('TODO: Support non-isolated groups.');
      }

      // TODO knockout - supposedly possible with the clever use of compositing
      // modes.
      if (group.knockout) {
        warn('Knockout groups not supported.');
      }

      var currentTransform = currentCtx.mozCurrentTransform;
      if (group.matrix) {
        currentCtx.transform.apply(currentCtx, group.matrix);
      }
      assert(group.bbox, 'Bounding box is required.');

      // Based on the current transform figure out how big the bounding box
      // will actually be.
      var bounds = Util.getAxialAlignedBoundingBox(
                    group.bbox,
                    currentCtx.mozCurrentTransform);
      // Clip the bounding box to the current canvas.
      var canvasBounds = [0,
                          0,
                          currentCtx.canvas.width,
                          currentCtx.canvas.height];
      bounds = Util.intersect(bounds, canvasBounds) || [0, 0, 0, 0];
      // Use ceil in case we're between sizes so we don't create canvas that is
      // too small and make the canvas at least 1x1 pixels.
      var offsetX = Math.floor(bounds[0]);
      var offsetY = Math.floor(bounds[1]);
      var drawnWidth = Math.max(Math.ceil(bounds[2]) - offsetX, 1);
      var drawnHeight = Math.max(Math.ceil(bounds[3]) - offsetY, 1);
      var scaleX = 1, scaleY = 1;
      if (drawnWidth > MAX_GROUP_SIZE) {
        scaleX = drawnWidth / MAX_GROUP_SIZE;
        drawnWidth = MAX_GROUP_SIZE;
      }
      if (drawnHeight > MAX_GROUP_SIZE) {
        scaleY = drawnHeight / MAX_GROUP_SIZE;
        drawnHeight = MAX_GROUP_SIZE;
      }

      var cacheId = 'groupAt' + this.groupLevel;
      if (group.smask) {
        // Using two cache entries is case if masks are used one after another.
        cacheId +=  '_smask_' + ((this.smaskCounter++) % 2);
      }
      var scratchCanvas = CachedCanvases.getCanvas(
        cacheId, drawnWidth, drawnHeight, true);
      var groupCtx = scratchCanvas.context;

      // Since we created a new canvas that is just the size of the bounding box
      // we have to translate the group ctx.
      groupCtx.scale(1 / scaleX, 1 / scaleY);
      groupCtx.translate(-offsetX, -offsetY);
      groupCtx.transform.apply(groupCtx, currentTransform);

      if (group.smask) {
        // Saving state and cached mask to be used in setGState.
        this.smaskStack.push({
          canvas: scratchCanvas.canvas,
          context: groupCtx,
          offsetX: offsetX,
          offsetY: offsetY,
          scaleX: scaleX,
          scaleY: scaleY,
          subtype: group.smask.subtype,
          backdrop: group.smask.backdrop
        });
      } else {
        // Setup the current ctx so when the group is popped we draw it at the
        // right location.
        currentCtx.setTransform(1, 0, 0, 1, 0, 0);
        currentCtx.translate(offsetX, offsetY);
        currentCtx.scale(scaleX, scaleY);
      }
      // The transparency group inherits all off the current graphics state
      // except the blend mode, soft mask, and alpha constants.
      copyCtxState(currentCtx, groupCtx);
      this.ctx = groupCtx;
      this.setGState([
        ['BM', 'Normal'],
        ['ca', 1],
        ['CA', 1]
      ]);
      this.groupStack.push(currentCtx);
      this.groupLevel++;
    },

    endGroup: function CanvasGraphics_endGroup(group) {
      this.groupLevel--;
      var groupCtx = this.ctx;
      this.ctx = this.groupStack.pop();
      // Turn off image smoothing to avoid sub pixel interpolation which can
      // look kind of blurry for some pdfs.
      if (this.ctx.imageSmoothingEnabled !== undefined) {
        this.ctx.imageSmoothingEnabled = false;
      } else {
        this.ctx.mozImageSmoothingEnabled = false;
      }
      if (group.smask) {
        this.tempSMask = this.smaskStack.pop();
      } else {
        this.ctx.drawImage(groupCtx.canvas, 0, 0);
      }
      this.restore();
    },

    beginAnnotations: function CanvasGraphics_beginAnnotations() {
      this.save();
      this.current = new CanvasExtraState();
    },

    endAnnotations: function CanvasGraphics_endAnnotations() {
      this.restore();
    },

    beginAnnotation: function CanvasGraphics_beginAnnotation(rect, transform,
                                                             matrix) {
      this.save();

      if (isArray(rect) && 4 === rect.length) {
        var width = rect[2] - rect[0];
        var height = rect[3] - rect[1];
        this.rectangle(rect[0], rect[1], width, height);
        this.clip();
        this.endPath();
      }

      this.transform.apply(this, transform);
      this.transform.apply(this, matrix);
    },

    endAnnotation: function CanvasGraphics_endAnnotation() {
      this.restore();
    },

    paintJpegXObject: function CanvasGraphics_paintJpegXObject(objId, w, h) {
      var domImage = this.objs.get(objId);
      if (!domImage) {
        warn('Dependent image isn\'t ready yet');
        return;
      }

      this.save();

      var ctx = this.ctx;
      // scale the image to the unit square
      ctx.scale(1 / w, -1 / h);

      ctx.drawImage(domImage, 0, 0, domImage.width, domImage.height,
                    0, -h, w, h);
      if (this.imageLayer) {
        var currentTransform = ctx.mozCurrentTransformInverse;
        var position = this.getCanvasPosition(0, 0);
        this.imageLayer.appendImage({
          objId: objId,
          left: position[0],
          top: position[1],
          width: w / currentTransform[0],
          height: h / currentTransform[3]
        });
      }
      this.restore();
    },

    paintImageMaskXObject: function CanvasGraphics_paintImageMaskXObject(img) {
      var ctx = this.ctx;
      var width = img.width, height = img.height;

      var glyph = this.processingType3;

      if (COMPILE_TYPE3_GLYPHS && glyph && !('compiled' in glyph)) {
        var MAX_SIZE_TO_COMPILE = 1000;
        if (width <= MAX_SIZE_TO_COMPILE && height <= MAX_SIZE_TO_COMPILE) {
          glyph.compiled =
            compileType3Glyph({data: img.data, width: width, height: height});
        } else {
          glyph.compiled = null;
        }
      }

      if (glyph && glyph.compiled) {
        glyph.compiled(ctx);
        return;
      }

      var maskCanvas = CachedCanvases.getCanvas('maskCanvas', width, height);
      var maskCtx = maskCanvas.context;
      maskCtx.save();

      putBinaryImageMask(maskCtx, img);

      maskCtx.globalCompositeOperation = 'source-in';

      var fillColor = this.current.fillColor;
      maskCtx.fillStyle = (fillColor && fillColor.hasOwnProperty('type') &&
                          fillColor.type === 'Pattern') ?
                          fillColor.getPattern(maskCtx, this) : fillColor;
      maskCtx.fillRect(0, 0, width, height);

      maskCtx.restore();

      this.paintInlineImageXObject(maskCanvas.canvas);
    },

    paintImageMaskXObjectRepeat:
      function CanvasGraphics_paintImageMaskXObjectRepeat(imgData, scaleX,
                                                          scaleY, positions) {
      var width = imgData.width;
      var height = imgData.height;
      var ctx = this.ctx;

      var maskCanvas = CachedCanvases.getCanvas('maskCanvas', width, height);
      var maskCtx = maskCanvas.context;
      maskCtx.save();

      putBinaryImageMask(maskCtx, imgData);

      maskCtx.globalCompositeOperation = 'source-in';

      var fillColor = this.current.fillColor;
      maskCtx.fillStyle = (fillColor && fillColor.hasOwnProperty('type') &&
        fillColor.type === 'Pattern') ?
        fillColor.getPattern(maskCtx, this) : fillColor;
      maskCtx.fillRect(0, 0, width, height);

      maskCtx.restore();

      for (var i = 0, ii = positions.length; i < ii; i += 2) {
        ctx.save();
        ctx.transform(scaleX, 0, 0, scaleY, positions[i], positions[i + 1]);
        ctx.scale(1, -1);
        ctx.drawImage(maskCanvas.canvas, 0, 0, width, height,
          0, -1, 1, 1);
        ctx.restore();
      }
    },

    paintImageMaskXObjectGroup:
      function CanvasGraphics_paintImageMaskXObjectGroup(images) {
      var ctx = this.ctx;

      for (var i = 0, ii = images.length; i < ii; i++) {
        var image = images[i];
        var width = image.width, height = image.height;

        var maskCanvas = CachedCanvases.getCanvas('maskCanvas', width, height);
        var maskCtx = maskCanvas.context;
        maskCtx.save();

        putBinaryImageMask(maskCtx, image);

        maskCtx.globalCompositeOperation = 'source-in';

        var fillColor = this.current.fillColor;
        maskCtx.fillStyle = (fillColor && fillColor.hasOwnProperty('type') &&
                            fillColor.type === 'Pattern') ?
                            fillColor.getPattern(maskCtx, this) : fillColor;
        maskCtx.fillRect(0, 0, width, height);

        maskCtx.restore();

        ctx.save();
        ctx.transform.apply(ctx, image.transform);
        ctx.scale(1, -1);
        ctx.drawImage(maskCanvas.canvas, 0, 0, width, height,
                      0, -1, 1, 1);
        ctx.restore();
      }
    },

    paintImageXObject: function CanvasGraphics_paintImageXObject(objId) {
      var imgData = this.objs.get(objId);
      if (!imgData) {
        warn('Dependent image isn\'t ready yet');
        return;
      }

      this.paintInlineImageXObject(imgData);
    },

    paintImageXObjectRepeat:
      function CanvasGraphics_paintImageXObjectRepeat(objId, scaleX, scaleY,
                                                          positions) {
      var imgData = this.objs.get(objId);
      if (!imgData) {
        warn('Dependent image isn\'t ready yet');
        return;
      }

      var width = imgData.width;
      var height = imgData.height;
      var map = [];
      for (var i = 0, ii = positions.length; i < ii; i += 2) {
        map.push({transform: [scaleX, 0, 0, scaleY, positions[i],
                 positions[i + 1]], x: 0, y: 0, w: width, h: height});
      }
      this.paintInlineImageXObjectGroup(imgData, map);
    },

    paintInlineImageXObject:
      function CanvasGraphics_paintInlineImageXObject(imgData) {
      var width = imgData.width;
      var height = imgData.height;
      var ctx = this.ctx;

      this.save();
      // scale the image to the unit square
      ctx.scale(1 / width, -1 / height);

      var currentTransform = ctx.mozCurrentTransformInverse;
      var a = currentTransform[0], b = currentTransform[1];
      var widthScale = Math.max(Math.sqrt(a * a + b * b), 1);
      var c = currentTransform[2], d = currentTransform[3];
      var heightScale = Math.max(Math.sqrt(c * c + d * d), 1);

      var imgToPaint, tmpCanvas;
      // instanceof HTMLElement does not work in jsdom node.js module
      if (imgData instanceof HTMLElement || !imgData.data) {
        imgToPaint = imgData;
      } else {
        tmpCanvas = CachedCanvases.getCanvas('inlineImage', width, height);
        var tmpCtx = tmpCanvas.context;
        putBinaryImageData(tmpCtx, imgData);
        imgToPaint = tmpCanvas.canvas;
      }

      var paintWidth = width, paintHeight = height;
      var tmpCanvasId = 'prescale1';
      // Vertial or horizontal scaling shall not be more than 2 to not loose the
      // pixels during drawImage operation, painting on the temporary canvas(es)
      // that are twice smaller in size
      while ((widthScale > 2 && paintWidth > 1) ||
             (heightScale > 2 && paintHeight > 1)) {
        var newWidth = paintWidth, newHeight = paintHeight;
        if (widthScale > 2 && paintWidth > 1) {
          newWidth = Math.ceil(paintWidth / 2);
          widthScale /= paintWidth / newWidth;
        }
        if (heightScale > 2 && paintHeight > 1) {
          newHeight = Math.ceil(paintHeight / 2);
          heightScale /= paintHeight / newHeight;
        }
        tmpCanvas = CachedCanvases.getCanvas(tmpCanvasId, newWidth, newHeight);
        tmpCtx = tmpCanvas.context;
        tmpCtx.clearRect(0, 0, newWidth, newHeight);
        tmpCtx.drawImage(imgToPaint, 0, 0, paintWidth, paintHeight,
                                     0, 0, newWidth, newHeight);
        imgToPaint = tmpCanvas.canvas;
        paintWidth = newWidth;
        paintHeight = newHeight;
        tmpCanvasId = tmpCanvasId === 'prescale1' ? 'prescale2' : 'prescale1';
      }
      ctx.drawImage(imgToPaint, 0, 0, paintWidth, paintHeight,
                                0, -height, width, height);

      if (this.imageLayer) {
        var position = this.getCanvasPosition(0, -height);
        this.imageLayer.appendImage({
          imgData: imgData,
          left: position[0],
          top: position[1],
          width: width / currentTransform[0],
          height: height / currentTransform[3]
        });
      }
      this.restore();
    },

    paintInlineImageXObjectGroup:
      function CanvasGraphics_paintInlineImageXObjectGroup(imgData, map) {
      var ctx = this.ctx;
      var w = imgData.width;
      var h = imgData.height;

      var tmpCanvas = CachedCanvases.getCanvas('inlineImage', w, h);
      var tmpCtx = tmpCanvas.context;
      putBinaryImageData(tmpCtx, imgData);

      for (var i = 0, ii = map.length; i < ii; i++) {
        var entry = map[i];
        ctx.save();
        ctx.transform.apply(ctx, entry.transform);
        ctx.scale(1, -1);
        ctx.drawImage(tmpCanvas.canvas, entry.x, entry.y, entry.w, entry.h,
                      0, -1, 1, 1);
        if (this.imageLayer) {
          var position = this.getCanvasPosition(entry.x, entry.y);
          this.imageLayer.appendImage({
            imgData: imgData,
            left: position[0],
            top: position[1],
            width: w,
            height: h
          });
        }
        ctx.restore();
      }
    },

    paintSolidColorImageMask:
      function CanvasGraphics_paintSolidColorImageMask() {
        this.ctx.fillRect(0, 0, 1, 1);
    },

    // Marked content

    markPoint: function CanvasGraphics_markPoint(tag) {
      // TODO Marked content.
    },
    markPointProps: function CanvasGraphics_markPointProps(tag, properties) {
      // TODO Marked content.
    },
    beginMarkedContent: function CanvasGraphics_beginMarkedContent(tag) {
      // TODO Marked content.
    },
    beginMarkedContentProps: function CanvasGraphics_beginMarkedContentProps(
                                        tag, properties) {
      // TODO Marked content.
    },
    endMarkedContent: function CanvasGraphics_endMarkedContent() {
      // TODO Marked content.
    },

    // Compatibility

    beginCompat: function CanvasGraphics_beginCompat() {
      // TODO ignore undefined operators (should we do that anyway?)
    },
    endCompat: function CanvasGraphics_endCompat() {
      // TODO stop ignoring undefined operators
    },

    // Helper functions

    consumePath: function CanvasGraphics_consumePath() {
      var ctx = this.ctx;
      if (this.pendingClip) {
        if (this.pendingClip === EO_CLIP) {
          if (ctx.mozFillRule !== undefined) {
            ctx.mozFillRule = 'evenodd';
            ctx.clip();
            ctx.mozFillRule = 'nonzero';
          } else {
            try {
              ctx.clip('evenodd');
            } catch (ex) {
              // shouldn't really happen, but browsers might think differently
              ctx.clip();
            }
          }
        } else {
          ctx.clip();
        }
        this.pendingClip = null;
      }
      ctx.beginPath();
    },
    getSinglePixelWidth: function CanvasGraphics_getSinglePixelWidth(scale) {
      var inverse = this.ctx.mozCurrentTransformInverse;
      // max of the current horizontal and vertical scale
      return Math.sqrt(Math.max(
        (inverse[0] * inverse[0] + inverse[1] * inverse[1]),
        (inverse[2] * inverse[2] + inverse[3] * inverse[3])));
    },
    getCanvasPosition: function CanvasGraphics_getCanvasPosition(x, y) {
        var transform = this.ctx.mozCurrentTransform;
        return [
          transform[0] * x + transform[2] * y + transform[4],
          transform[1] * x + transform[3] * y + transform[5]
        ];
    }
  };

  for (var op in OPS) {
    CanvasGraphics.prototype[OPS[op]] = CanvasGraphics.prototype[op];
  }

  return CanvasGraphics;
})();