image.smoothing.worker.js

// spec link: https://html.spec.whatwg.org/#the-offscreen-2d-rendering-context

importScripts("/resources/testharness.js");

function createTestImage() {
  var image = new OffscreenCanvas(100, 50);
  var imgctx = image.getContext('2d');
  imgctx.fillStyle = "#F00";
  imgctx.fillRect(0, 0, 2, 2);
  imgctx.fillStyle = "#0F0";
  imgctx.fillRect(0, 0, 1, 1);
  return image;
}

test(function() {
  var offscreenCanvas = new OffscreenCanvas(100, 50);
  var ctx = offscreenCanvas.getContext('2d');
  assert_true(ctx.imageSmoothingEnabled);
}, "When the context is created, imageSmoothingEnabled must be set to true.");

test(function() {
  var offscreenCanvas = new OffscreenCanvas(100, 50);
  var ctx = offscreenCanvas.getContext('2d');
  ctx.imageSmoothingEnabled = false;
  assert_false(ctx.imageSmoothingEnabled);
}, "On getting imageSmoothingEnabled, the user agent must return the last value it was set to.");

test(function() {
  var offscreenCanvas = new OffscreenCanvas(100, 50);
  var ctx = offscreenCanvas.getContext('2d');
  var image = createTestImage();
  ctx.scale(10, 10);
  ctx.drawImage(image, 0, 0);
  var pixels = ctx.getImageData(9, 9, 1, 1).data;
  assert_not_equals(pixels[0], 0);
  assert_not_equals(pixels[1], 255);
}, "Test that image smoothing is actually on by default.");

test(function() {
  var offscreenCanvas = new OffscreenCanvas(100, 50);
  var ctx = offscreenCanvas.getContext('2d');
  ctx.imageSmoothingEnabled = true;
  var image = createTestImage();
  ctx.scale(10, 10);
  ctx.drawImage(image, 0, 0);
  var pixels = ctx.getImageData(9, 9, 1, 1).data;
  assert_not_equals(pixels[0], 0);
  assert_not_equals(pixels[1], 255);
}, "Test that image smoothing works when imageSmoothingEnabled is set to true");

test(function() {
  var offscreenCanvas = new OffscreenCanvas(100, 50);
  var ctx = offscreenCanvas.getContext('2d');
  var image = createTestImage();
  ctx.imageSmoothingEnabled = false;
  ctx.scale(10, 10);
  ctx.drawImage(image, 0, 0);
  var pixels = ctx.getImageData(9, 9, 1, 1).data;
  assert_array_equals(pixels, [0, 255, 0, 255]);
}, "Test that imageSmoothingEnabled = false (nearest-neighbor interpolation) works with drawImage().");

test(function() {
  var offscreenCanvas = new OffscreenCanvas(100, 50);
  var ctx = offscreenCanvas.getContext('2d');
  var image = createTestImage();
  ctx.imageSmoothingEnabled = false;
  ctx.scale(10, 10);
  ctx.fillStyle = ctx.createPattern(image, 'repeat');
  ctx.fillRect(0, 0, 10, 10);
  var pixels = ctx.getImageData(9, 9, 1, 1).data;
  assert_array_equals(pixels, [0, 255, 0, 255]);
}, "Test that imageSmoothingEnabled = false (nearest-neighbor interpolation) works with fillRect and createPattern().");

test(function() {
  var offscreenCanvas = new OffscreenCanvas(100, 50);
  var ctx = offscreenCanvas.getContext('2d');
  var image = createTestImage();
  ctx.imageSmoothingEnabled = false;
  ctx.fillStyle = ctx.createPattern(image, 'repeat');
  ctx.scale(10, 10);
  ctx.rect(0, 0, 10, 10);
  ctx.fill();
  var pixels = ctx.getImageData(9, 9, 1, 1).data;
  assert_array_equals(pixels, [0, 255, 0, 255]);
}, "Test that imageSmoothingEnabled = false (nearest-neighbor interpolation) works with fill() and createPattern().");

test(function() {
  var offscreenCanvas = new OffscreenCanvas(100, 50);
  var ctx = offscreenCanvas.getContext('2d');
  var image = createTestImage();
  ctx.strokeStyle = ctx.createPattern(image, 'repeat');
  ctx.lineWidth = 5;
  ctx.imageSmoothingEnabled = false;
  ctx.scale(10, 10);
  ctx.beginPath();
  ctx.moveTo(0, 0);
  ctx.lineTo(10, 10);
  ctx.stroke();
  var pixels = ctx.getImageData(9, 9, 1, 1).data;
  assert_array_equals(pixels, [0, 255, 0, 255]);
}, "Test that imageSmoothingEnabled = false (nearest-neighbor interpolation) works with stroke() and createPattern().");

test(function() {
  var repaints = 5;
  var offscreenCanvas = new OffscreenCanvas(100, 50);
  var ctx = offscreenCanvas.getContext('2d');

  function draw() {
    ctx.clearRect(0, 0, 10, 10);
    ctx.setTransform(1, 0, 0, 1, 0, 0);
    var image = createTestImage();
    ctx.imageSmoothingEnabled = false;
    ctx.scale(10, 10);
    ctx.drawImage(image, 0, 0);
    var pixels = ctx.getImageData(9, 9, 1, 1).data;
    assert_array_equals(pixels, [0, 255, 0, 255]);
  }

  while (repaints > 0) {
    draw();
    repaints = repaints - 1;
  }

}, "Test that imageSmoothingEnabled = false (nearest-neighbor interpolation) still works after repaints.");

done();