Add support for arbitrary rotation angle via vips_rotate (#1385)

docs/api-operation.md

@@ -5,9 +5,12 @@
 Rotate the output image by either an explicit angle
 or auto-orient based on the EXIF `Orientation` tag.
 
-If an angle is provided, it is converted to a valid 90/180/270deg rotation.
+If an angle is provided, it is converted to a valid positive degree rotation.
 For example, `-450` will produce a 270deg rotation.
 
+If an angle that is not a multiple of 90 is provided, the color of the
+background color can be provided with the `background` option.
+
 If no angle is provided, it is determined from the EXIF data.
 Mirroring is supported and may infer the use of a flip operation.
 
@@ -19,6 +22,8 @@ for example `rotate(x).extract(y)` will produce a different result to `extract(y
 ### Parameters
 
 -   `angle` **[Number][1]** angle of rotation, must be a multiple of 90. (optional, default `auto`)
+-   `options` **[Object][2]?** if present, is an Object with optional attributes.
+    -   `options.background` **([String][3] \| [Object][2])** parsed by the [color][4] module to extract values for red, green, blue and alpha. (optional, default `"#000000"`)
 
 ### Examples
 
@@ -34,7 +39,7 @@ const pipeline = sharp()
 readableStream.pipe(pipeline);
 ```
 
--   Throws **[Error][2]** Invalid parameters
+-   Throws **[Error][5]** Invalid parameters
 
 Returns **Sharp** 
 
@@ -45,7 +50,7 @@ The use of `flip` implies the removal of the EXIF `Orientation` tag, if any.
 
 ### Parameters
 
--   `flip` **[Boolean][3]**  (optional, default `true`)
+-   `flip` **[Boolean][6]**  (optional, default `true`)
 
 Returns **Sharp** 
 
@@ -56,7 +61,7 @@ The use of `flop` implies the removal of the EXIF `Orientation` tag, if any.
 
 ### Parameters
 
--   `flop` **[Boolean][3]**  (optional, default `true`)
+-   `flop` **[Boolean][6]**  (optional, default `true`)
 
 Returns **Sharp** 
 
@@ -74,7 +79,7 @@ Separate control over the level of sharpening in "flat" and "jagged" areas is av
 -   `jagged` **[Number][1]** the level of sharpening to apply to "jagged" areas. (optional, default `2.0`)
 
 
--   Throws **[Error][2]** Invalid parameters
+-   Throws **[Error][5]** Invalid parameters
 
 Returns **Sharp** 
 
@@ -88,7 +93,7 @@ When used without parameters the default window is 3x3.
 -   `size` **[Number][1]** square mask size: size x size (optional, default `3`)
 
 
--   Throws **[Error][2]** Invalid parameters
+-   Throws **[Error][5]** Invalid parameters
 
 Returns **Sharp** 
 
@@ -103,7 +108,7 @@ When a `sigma` is provided, performs a slower, more accurate Gaussian blur.
 -   `sigma` **[Number][1]?** a value between 0.3 and 1000 representing the sigma of the Gaussian mask, where `sigma = 1 + radius / 2`.
 
 
--   Throws **[Error][2]** Invalid parameters
+-   Throws **[Error][5]** Invalid parameters
 
 Returns **Sharp** 
 
@@ -113,7 +118,7 @@ Merge alpha transparency channel, if any, with `background`.
 
 ### Parameters
 
--   `flatten` **[Boolean][3]**  (optional, default `true`)
+-   `flatten` **[Boolean][6]**  (optional, default `true`)
 
 Returns **Sharp** 
 
@@ -130,7 +135,7 @@ when applying a gamma correction.
 -   `gamma` **[Number][1]** value between 1.0 and 3.0. (optional, default `2.2`)
 
 
--   Throws **[Error][2]** Invalid parameters
+-   Throws **[Error][5]** Invalid parameters
 
 Returns **Sharp** 
 
@@ -140,7 +145,7 @@ Produce the "negative" of the image.
 
 ### Parameters
 
--   `negate` **[Boolean][3]**  (optional, default `true`)
+-   `negate` **[Boolean][6]**  (optional, default `true`)
 
 Returns **Sharp** 
 
@@ -150,7 +155,7 @@ Enhance output image contrast by stretching its luminance to cover the full dyna
 
 ### Parameters
 
--   `normalise` **[Boolean][3]**  (optional, default `true`)
+-   `normalise` **[Boolean][6]**  (optional, default `true`)
 
 Returns **Sharp** 
 
@@ -160,7 +165,7 @@ Alternative spelling of normalise.
 
 ### Parameters
 
--   `normalize` **[Boolean][3]**  (optional, default `true`)
+-   `normalize` **[Boolean][6]**  (optional, default `true`)
 
 Returns **Sharp** 
 
@@ -170,10 +175,10 @@ Convolve the image with the specified kernel.
 
 ### Parameters
 
--   `kernel` **[Object][4]** 
+-   `kernel` **[Object][2]** 
     -   `kernel.width` **[Number][1]** width of the kernel in pixels.
     -   `kernel.height` **[Number][1]** width of the kernel in pixels.
-    -   `kernel.kernel` **[Array][5]<[Number][1]>** Array of length `width*height` containing the kernel values.
+    -   `kernel.kernel` **[Array][7]<[Number][1]>** Array of length `width*height` containing the kernel values.
     -   `kernel.scale` **[Number][1]** the scale of the kernel in pixels. (optional, default `sum`)
     -   `kernel.offset` **[Number][1]** the offset of the kernel in pixels. (optional, default `0`)
 
@@ -193,7 +198,7 @@ sharp(input)
   });
 ```
 
--   Throws **[Error][2]** Invalid parameters
+-   Throws **[Error][5]** Invalid parameters
 
 Returns **Sharp** 
 
@@ -204,12 +209,12 @@ Any pixel value greather than or equal to the threshold value will be set to 255
 ### Parameters
 
 -   `threshold` **[Number][1]** a value in the range 0-255 representing the level at which the threshold will be applied. (optional, default `128`)
--   `options` **[Object][4]?** 
-    -   `options.greyscale` **[Boolean][3]** convert to single channel greyscale. (optional, default `true`)
-    -   `options.grayscale` **[Boolean][3]** alternative spelling for greyscale. (optional, default `true`)
+-   `options` **[Object][2]?** 
+    -   `options.greyscale` **[Boolean][6]** convert to single channel greyscale. (optional, default `true`)
+    -   `options.grayscale` **[Boolean][6]** alternative spelling for greyscale. (optional, default `true`)
 
 
--   Throws **[Error][2]** Invalid parameters
+-   Throws **[Error][5]** Invalid parameters
 
 Returns **Sharp** 
 
@@ -222,16 +227,16 @@ the selected bitwise boolean `operation` between the corresponding pixels of the
 
 ### Parameters
 
--   `operand` **([Buffer][6] \| [String][7])** Buffer containing image data or String containing the path to an image file.
--   `operator` **[String][7]** one of `and`, `or` or `eor` to perform that bitwise operation, like the C logic operators `&`, `|` and `^` respectively.
--   `options` **[Object][4]?** 
-    -   `options.raw` **[Object][4]?** describes operand when using raw pixel data.
+-   `operand` **([Buffer][8] \| [String][3])** Buffer containing image data or String containing the path to an image file.
+-   `operator` **[String][3]** one of `and`, `or` or `eor` to perform that bitwise operation, like the C logic operators `&`, `|` and `^` respectively.
+-   `options` **[Object][2]?** 
+    -   `options.raw` **[Object][2]?** describes operand when using raw pixel data.
         -   `options.raw.width` **[Number][1]?** 
         -   `options.raw.height` **[Number][1]?** 
         -   `options.raw.channels` **[Number][1]?** 
 
 
--   Throws **[Error][2]** Invalid parameters
+-   Throws **[Error][5]** Invalid parameters
 
 Returns **Sharp** 
 
@@ -245,20 +250,22 @@ Apply the linear formula a \* input + b to the image (levels adjustment)
 -   `b` **[Number][1]** offset (optional, default `0.0`)
 
 
--   Throws **[Error][2]** Invalid parameters
+-   Throws **[Error][5]** Invalid parameters
 
 Returns **Sharp** 
 
 [1]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number
 
-[2]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Error
+[2]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object
+
+[3]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String
 
-[3]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean
+[4]: https://www.npmjs.org/package/color
 
-[4]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object
+[5]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Error
 
-[5]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Array
+[6]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean
 
-[6]: https://nodejs.org/api/buffer.html
+[7]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Array
 
-[7]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String
+[8]: https://nodejs.org/api/buffer.html

lib/constructor.js

@@ -108,6 +108,8 @@ const Sharp = function (input, options) {
     embed: 0,
     useExifOrientation: false,
     angle: 0,
+    rotationAngle: 0,
+    rotationBackground: [0, 0, 0, 255],
     rotateBeforePreExtract: false,
     flip: false,
     flop: false,

lib/operation.js

@@ -1,14 +1,18 @@
 'use strict';
 
+const color = require('color');
 const is = require('./is');
 
 /**
  * Rotate the output image by either an explicit angle
  * or auto-orient based on the EXIF `Orientation` tag.
  *
- * If an angle is provided, it is converted to a valid 90/180/270deg rotation.
+ * If an angle is provided, it is converted to a valid positive degree rotation.
  * For example, `-450` will produce a 270deg rotation.
  *
+ * If an angle that is not a multiple of 90 is provided, the color of the
+ * background color can be provided with the `background` option.
+ *
  * If no angle is provided, it is determined from the EXIF data.
  * Mirroring is supported and may infer the use of a flip operation.
  *
@@ -29,16 +33,29 @@ const is = require('./is');
  * readableStream.pipe(pipeline);
  *
  * @param {Number} [angle=auto] angle of rotation, must be a multiple of 90.
+ * @param {Object} [options] - if present, is an Object with optional attributes.
+ * @param {String|Object} [options.background="#000000"] parsed by the [color](https://www.npmjs.org/package/color) module to extract values for red, green, blue and alpha.
  * @returns {Sharp}
  * @throws {Error} Invalid parameters
  */
-function rotate (angle) {
+function rotate (angle, options) {
   if (!is.defined(angle)) {
     this.options.useExifOrientation = true;
   } else if (is.integer(angle) && !(angle % 90)) {
     this.options.angle = angle;
+  } else if (is.number(angle)) {
+    this.options.rotationAngle = angle;
+    if (is.object(options) && options.background) {
+      const backgroundColour = color(options.background);
+      this.options.rotationBackground = [
+        backgroundColour.red(),
+        backgroundColour.green(),
+        backgroundColour.blue(),
+        Math.round(backgroundColour.alpha() * 255)
+      ];
+    }
   } else {
-    throw new Error('Unsupported angle: angle must be a positive/negative multiple of 90 ' + angle);
+    throw new Error('Unsupported angle: angle must be a number.');
   }
   return this;
 }

src/pipeline.cc

@@ -476,6 +476,13 @@ class PipelineWorker : public Nan::AsyncWorker {
         }
       }
 
+      // Rotate by degree
+      if (baton->rotationAngle != 0.0) {
+        std::vector<double> background;
+        std::tie(image, background) = sharp::ApplyAlpha(image, baton->rotationBackground);
+        image = image.rotate(baton->rotationAngle, VImage::option()->set("background", background));
+      }
+
       // Post extraction
       if (baton->topOffsetPost != -1) {
         image = image.extract_area(
@@ -1187,6 +1194,12 @@ NAN_METHOD(pipeline) {
   baton->normalise = AttrTo<bool>(options, "normalise");
   baton->useExifOrientation = AttrTo<bool>(options, "useExifOrientation");
   baton->angle = AttrTo<int32_t>(options, "angle");
+  baton->rotationAngle = AttrTo<double>(options, "rotationAngle");
+  // Rotation background colour
+  v8::Local<v8::Object> rotationBackground = AttrAs<v8::Object>(options, "rotationBackground");
+  for (unsigned int i = 0; i < 4; i++) {
+    baton->rotationBackground[i] = AttrTo<double>(rotationBackground, i);
+  }
   baton->rotateBeforePreExtract = AttrTo<bool>(options, "rotateBeforePreExtract");
   baton->flip = AttrTo<bool>(options, "flip");
   baton->flop = AttrTo<bool>(options, "flop");

src/pipeline.h

@@ -89,6 +89,8 @@ struct PipelineBaton {
   bool normalise;
   bool useExifOrientation;
   int angle;
+  double rotationAngle;
+  double rotationBackground[4];
   bool rotateBeforePreExtract;
   bool flip;
   bool flop;
@@ -180,6 +182,7 @@ struct PipelineBaton {
     normalise(false),
     useExifOrientation(false),
     angle(0),
+    rotationAngle(0.0),
     flip(false),
     flop(false),
     extendTop(0),