Add composite op, supporting multiple images and blend modes #728

docs/api-composite.md

@@ -1,33 +1,41 @@
 <!-- Generated by documentation.js. Update this documentation by updating the source code. -->
 
-## overlayWith
+## composite
 
-Overlay (composite) an image over the processed (resized, extracted etc.) image.
+Composite image(s) over the processed (resized, extracted etc.) image.
 
-The overlay image must be the same size or smaller than the processed image.
+The images to composite must be the same size or smaller than the processed image.
 If both `top` and `left` options are provided, they take precedence over `gravity`.
 
-If the overlay image contains an alpha channel then composition with premultiplication will occur.
+The `blend` option can be one of `clear`, `source`, `over`, `in`, `out`, `atop`,
+`dest`, `dest-over`, `dest-in`, `dest-out`, `dest-atop`,
+`xor`, `add`, `saturate`, `multiply`, `screen`, `overlay`, `darken`, `lighten`,
+`colour-dodge`, `color-dodge`, `colour-burn`,`color-burn`,
+`hard-light`, `soft-light`, `difference`, `exclusion`.
+
+More information about blend modes can be found at
+[https://libvips.github.io/libvips/API/current/libvips-conversion.html#VipsBlendMode][1]
+and [https://www.cairographics.org/operators/][2]
 
 ### Parameters
 
--   `overlay` **([Buffer][1] \| [String][2])?** Buffer containing image data or String containing the path to an image file.
+-   `images` **[Array][3]&lt;[Object][4]>** Ordered list of images to composite
--   `options` **[Object][3]?** 
+    -   `images[].input` **([Buffer][5] \| [String][6])?** Buffer containing image data or String containing the path to an image file.
-    -   `options.gravity` **[String][2]** gravity at which to place the overlay. (optional, default `'centre'`)
+    -   `images[].blend` **[String][6]** how to blend this image with the image below. (optional, default `'over'`)
-    -   `options.top` **[Number][4]?** the pixel offset from the top edge.
+    -   `images[].gravity` **[String][6]** gravity at which to place the overlay. (optional, default `'centre'`)
-    -   `options.left` **[Number][4]?** the pixel offset from the left edge.
+    -   `images[].top` **[Number][7]?** the pixel offset from the top edge.
-    -   `options.tile` **[Boolean][5]** set to true to repeat the overlay image across the entire image with the given `gravity`. (optional, default `false`)
+    -   `images[].left` **[Number][7]?** the pixel offset from the left edge.
-    -   `options.cutout` **[Boolean][5]** set to true to apply only the alpha channel of the overlay image to the input image, giving the appearance of one image being cut out of another. (optional, default `false`)
+    -   `images[].tile` **[Boolean][8]** set to true to repeat the overlay image across the entire image with the given `gravity`. (optional, default `false`)
-    -   `options.density` **[Number][4]** number representing the DPI for vector overlay image. (optional, default `72`)
+    -   `images[].density` **[Number][7]** number representing the DPI for vector overlay image. (optional, default `72`)
-    -   `options.raw` **[Object][3]?** describes overlay when using raw pixel data.
+    -   `images[].raw` **[Object][4]?** describes overlay when using raw pixel data.
-        -   `options.raw.width` **[Number][4]?** 
+        -   `images[].raw.width` **[Number][7]?** 
-        -   `options.raw.height` **[Number][4]?** 
+        -   `images[].raw.height` **[Number][7]?** 
-        -   `options.raw.channels` **[Number][4]?** 
+        -   `images[].raw.channels` **[Number][7]?** 
-    -   `options.create` **[Object][3]?** describes a blank overlay to be created.
+    -   `images[].create` **[Object][4]?** describes a blank overlay to be created.
-        -   `options.create.width` **[Number][4]?** 
+        -   `images[].create.width` **[Number][7]?** 
-        -   `options.create.height` **[Number][4]?** 
+        -   `images[].create.height` **[Number][7]?** 
-        -   `options.create.channels` **[Number][4]?** 3-4
+        -   `images[].create.channels` **[Number][7]?** 3-4
-        -   `options.create.background` **([String][2] \| [Object][3])?** parsed by the [color][6] module to extract values for red, green, blue and alpha.
+        -   `images[].create.background` **([String][6] \| [Object][4])?** parsed by the [color][9] module to extract values for red, green, blue and alpha.
 
 ### Examples
 
@@ -36,7 +44,7 @@ sharp('input.png')
   .rotate(180)
   .resize(300)
   .flatten( { background: '#ff6600' } )
-  .overlayWith('overlay.png', { gravity: sharp.gravity.southeast } )
+  .composite([{ input: 'overlay.png', gravity: 'southeast' }])
   .sharpen()
   .withMetadata()
   .webp( { quality: 90 } )
@@ -48,20 +56,26 @@ sharp('input.png')
   });
 ```
 
--   Throws **[Error][7]** Invalid parameters
+-   Throws **[Error][10]** Invalid parameters
 
 Returns **Sharp** 
 
-[1]: https://nodejs.org/api/buffer.html
+[1]: https://libvips.github.io/libvips/API/current/libvips-conversion.html#VipsBlendMode
 
-[2]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String
+[2]: https://www.cairographics.org/operators/
 
-[3]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object
+[3]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Array
 
-[4]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number
+[4]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object
 
-[5]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean
+[5]: https://nodejs.org/api/buffer.html
 
-[6]: https://www.npmjs.org/package/color
+[6]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String
 
-[7]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Error
+[7]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number
+
+[8]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean
+
+[9]: https://www.npmjs.org/package/color
+
+[10]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Error

docs/changelog.md

@@ -9,6 +9,9 @@ Requires libvips v8.7.4.
 * Remove functions previously deprecated in v0.21.0:
     `background`, `crop`, `embed`, `ignoreAspectRatio`, `max`, `min` and `withoutEnlargement`.
 
+* Add `composite` operation supporting multiple images and blend modes; deprecate `overlayWith`.
+  [#728](https://github.com/lovell/sharp/issues/728)
+
 ### v0.21 - "*teeth*"
 
 Requires libvips v8.7.0.

lib/composite.js

@@ -1,21 +1,66 @@
 'use strict';
 
+const deprecate = require('util').deprecate;
+
 const is = require('./is');
 
 /**
- * Overlay (composite) an image over the processed (resized, extracted etc.) image.
+ * Blend modes.
+ * @member
+ * @private
+ */
+const blend = {
+  clear: 'clear',
+  source: 'source',
+  over: 'over',
+  in: 'in',
+  out: 'out',
+  atop: 'atop',
+  dest: 'dest',
+  'dest-over': 'dest-over',
+  'dest-in': 'dest-in',
+  'dest-out': 'dest-out',
+  'dest-atop': 'dest-atop',
+  xor: 'xor',
+  add: 'add',
+  saturate: 'saturate',
+  multiply: 'multiply',
+  screen: 'screen',
+  overlay: 'overlay',
+  darken: 'darken',
+  lighten: 'lighten',
+  'colour-dodge': 'colour-dodge',
+  'color-dodge': 'colour-dodge',
+  'colour-burn': 'colour-burn',
+  'color-burn': 'colour-burn',
+  'hard-light': 'hard-light',
+  'soft-light': 'soft-light',
+  difference: 'difference',
+  exclusion: 'exclusion'
+};
+
+/**
+ * Composite image(s) over the processed (resized, extracted etc.) image.
  *
- * The overlay image must be the same size or smaller than the processed image.
+ * The images to composite must be the same size or smaller than the processed image.
  * If both `top` and `left` options are provided, they take precedence over `gravity`.
  *
- * If the overlay image contains an alpha channel then composition with premultiplication will occur.
+ * The `blend` option can be one of `clear`, `source`, `over`, `in`, `out`, `atop`,
+ * `dest`, `dest-over`, `dest-in`, `dest-out`, `dest-atop`,
+ * `xor`, `add`, `saturate`, `multiply`, `screen`, `overlay`, `darken`, `lighten`,
+ * `colour-dodge`, `color-dodge`, `colour-burn`,`color-burn`,
+ * `hard-light`, `soft-light`, `difference`, `exclusion`.
+ *
+ * More information about blend modes can be found at
+ * https://libvips.github.io/libvips/API/current/libvips-conversion.html#VipsBlendMode
+ * and https://www.cairographics.org/operators/
  *
  * @example
  * sharp('input.png')
  *   .rotate(180)
  *   .resize(300)
  *   .flatten( { background: '#ff6600' } )
- *   .overlayWith('overlay.png', { gravity: sharp.gravity.southeast } )
+ *   .composite([{ input: 'overlay.png', gravity: 'southeast' }])
  *   .sharpen()
  *   .withMetadata()
  *   .webp( { quality: 90 } )
@@ -26,70 +71,104 @@ const is = require('./is');
  *     // sharpened, with metadata, 90% quality WebP image data. Phew!
  *   });
  *
- * @param {(Buffer|String)} [overlay] - Buffer containing image data or String containing the path to an image file.
+ * @param {Object[]} images - Ordered list of images to composite
- * @param {Object} [options]
+ * @param {Buffer|String} [images[].input] - Buffer containing image data or String containing the path to an image file.
- * @param {String} [options.gravity='centre'] - gravity at which to place the overlay.
+ * @param {String} [images[].blend='over'] - how to blend this image with the image below.
- * @param {Number} [options.top] - the pixel offset from the top edge.
+ * @param {String} [images[].gravity='centre'] - gravity at which to place the overlay.
- * @param {Number} [options.left] - the pixel offset from the left edge.
+ * @param {Number} [images[].top] - the pixel offset from the top edge.
- * @param {Boolean} [options.tile=false] - set to true to repeat the overlay image across the entire image with the given `gravity`.
+ * @param {Number} [images[].left] - the pixel offset from the left edge.
- * @param {Boolean} [options.cutout=false] - set to true to apply only the alpha channel of the overlay image to the input image, giving the appearance of one image being cut out of another.
+ * @param {Boolean} [images[].tile=false] - set to true to repeat the overlay image across the entire image with the given `gravity`.
- * @param {Number} [options.density=72] - number representing the DPI for vector overlay image.
+ * @param {Number} [images[].density=72] - number representing the DPI for vector overlay image.
- * @param {Object} [options.raw] - describes overlay when using raw pixel data.
+ * @param {Object} [images[].raw] - describes overlay when using raw pixel data.
- * @param {Number} [options.raw.width]
+ * @param {Number} [images[].raw.width]
- * @param {Number} [options.raw.height]
+ * @param {Number} [images[].raw.height]
- * @param {Number} [options.raw.channels]
+ * @param {Number} [images[].raw.channels]
- * @param {Object} [options.create] - describes a blank overlay to be created.
+ * @param {Object} [images[].create] - describes a blank overlay to be created.
- * @param {Number} [options.create.width]
+ * @param {Number} [images[].create.width]
- * @param {Number} [options.create.height]
+ * @param {Number} [images[].create.height]
- * @param {Number} [options.create.channels] - 3-4
+ * @param {Number} [images[].create.channels] - 3-4
- * @param {String|Object} [options.create.background] - parsed by the [color](https://www.npmjs.org/package/color) module to extract values for red, green, blue and alpha.
+ * @param {String|Object} [images[].create.background] - 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 overlayWith (overlay, options) {
+function composite (images) {
-  this.options.overlay = this._createInputDescriptor(overlay, options, {
+  if (!Array.isArray(images)) {
-    allowStream: false
+    throw is.invalidParameterError('images to composite', 'array', images);
+  }
+  this.options.composite = images.map(image => {
+    if (!is.object(image)) {
+      throw is.invalidParameterError('image to composite', 'object', image);
+    }
+    const { raw, density } = image;
+    const inputOptions = (raw || density) ? { raw, density } : undefined;
+    const composite = {
+      input: this._createInputDescriptor(image.input, inputOptions, { allowStream: false }),
+      blend: 'over',
+      tile: false,
+      left: -1,
+      top: -1,
+      gravity: 0
+    };
+    if (is.defined(image.blend)) {
+      if (is.string(blend[image.blend])) {
+        composite.blend = blend[image.blend];
+      } else {
+        throw is.invalidParameterError('blend', 'valid blend name', image.blend);
+      }
+    }
+    if (is.defined(image.tile)) {
+      if (is.bool(image.tile)) {
+        composite.tile = image.tile;
+      } else {
+        throw is.invalidParameterError('tile', 'boolean', image.tile);
+      }
+    }
+    if (is.defined(image.left)) {
+      if (is.integer(image.left) && image.left >= 0) {
+        composite.left = image.left;
+      } else {
+        throw is.invalidParameterError('left', 'positive integer', image.left);
+      }
+    }
+    if (is.defined(image.top)) {
+      if (is.integer(image.top) && image.top >= 0) {
+        composite.top = image.top;
+      } else {
+        throw is.invalidParameterError('top', 'positive integer', image.top);
+      }
+    }
+    if (composite.left !== composite.top && Math.min(composite.left, composite.top) === -1) {
+      throw new Error('Expected both left and top to be set');
+    }
+    if (is.defined(image.gravity)) {
+      if (is.integer(image.gravity) && is.inRange(image.gravity, 0, 8)) {
+        composite.gravity = image.gravity;
+      } else if (is.string(image.gravity) && is.integer(this.constructor.gravity[image.gravity])) {
+        composite.gravity = this.constructor.gravity[image.gravity];
+      } else {
+        throw is.invalidParameterError('gravity', 'valid gravity', image.gravity);
+      }
+    }
+    return composite;
   });
-  if (is.object(options)) {
-    if (is.defined(options.tile)) {
-      if (is.bool(options.tile)) {
-        this.options.overlayTile = options.tile;
-      } else {
-        throw new Error('Invalid overlay tile ' + options.tile);
-      }
-    }
-    if (is.defined(options.cutout)) {
-      if (is.bool(options.cutout)) {
-        this.options.overlayCutout = options.cutout;
-      } else {
-        throw new Error('Invalid overlay cutout ' + options.cutout);
-      }
-    }
-    if (is.defined(options.left) || is.defined(options.top)) {
-      if (is.integer(options.left) && options.left >= 0 && is.integer(options.top) && options.top >= 0) {
-        this.options.overlayXOffset = options.left;
-        this.options.overlayYOffset = options.top;
-      } else {
-        throw new Error('Invalid overlay left ' + options.left + ' and/or top ' + options.top);
-      }
-    }
-    if (is.defined(options.gravity)) {
-      if (is.integer(options.gravity) && is.inRange(options.gravity, 0, 8)) {
-        this.options.overlayGravity = options.gravity;
-      } else if (is.string(options.gravity) && is.integer(this.constructor.gravity[options.gravity])) {
-        this.options.overlayGravity = this.constructor.gravity[options.gravity];
-      } else {
-        throw new Error('Unsupported overlay gravity ' + options.gravity);
-      }
-    }
-  }
   return this;
 }
 
+/**
+ * @deprecated
+ * @private
+ */
+function overlayWith (input, options) {
+  const blend = (is.object(options) && options.cutout) ? 'dest-in' : 'over';
+  return this.composite([Object.assign({ input, blend }, options)]);
+}
+
 /**
  * Decorate the Sharp prototype with composite-related functions.
  * @private
  */
 module.exports = function (Sharp) {
-  Sharp.prototype.overlayWith = overlayWith;
+  Sharp.prototype.composite = composite;
+  Sharp.prototype.overlayWith = deprecate(overlayWith, 'overlayWith(input, options) is deprecated, use composite([{ input, ...options }]) instead');
+  Sharp.blend = blend;
 };

lib/constructor.js

@@ -145,12 +145,7 @@ const Sharp = function (input, options) {
     removeAlpha: false,
     ensureAlpha: false,
     colourspace: 'srgb',
-    // overlay
+    composite: [],
-    overlayGravity: 0,
-    overlayXOffset: -1,
-    overlayYOffset: -1,
-    overlayTile: false,
-    overlayCutout: false,
     // output
     fileOut: '',
     formatOut: 'input',

src/operations.cc

@@ -50,130 +50,6 @@ namespace sharp {
     return image;
   }
 
-  /*
-    Composite overlayImage over image at given position
-    Assumes alpha channels are already premultiplied and will be unpremultiplied after
-   */
-  VImage Composite(VImage image, VImage overlayImage, int const left, int const top) {
-    if (HasAlpha(overlayImage)) {
-      // Alpha composite
-      if (overlayImage.width() < image.width() || overlayImage.height() < image.height()) {
-        // Enlarge overlay
-        std::vector<double> const background { 0.0, 0.0, 0.0, 0.0 };
-        overlayImage = overlayImage.embed(left, top, image.width(), image.height(), VImage::option()
-          ->set("extend", VIPS_EXTEND_BACKGROUND)
-          ->set("background", background));
-      }
-      return AlphaComposite(image, overlayImage);
-    } else {
-      if (HasAlpha(image)) {
-        // Add alpha channel to overlayImage so channels match
-        double const multiplier = sharp::Is16Bit(overlayImage.interpretation()) ? 256.0 : 1.0;
-        overlayImage = overlayImage.bandjoin(
-          VImage::new_matrix(overlayImage.width(), overlayImage.height()).new_from_image(255 * multiplier));
-      }
-      return image.insert(overlayImage, left, top);
-    }
-  }
-
-  VImage AlphaComposite(VImage dst, VImage src) {
-    // Split src into non-alpha and alpha channels
-    VImage srcWithoutAlpha = src.extract_band(0, VImage::option()->set("n", src.bands() - 1));
-    VImage srcAlpha = src[src.bands() - 1] * (1.0 / 255.0);
-
-    // Split dst into non-alpha and alpha channels
-    VImage dstWithoutAlpha = dst.extract_band(0, VImage::option()->set("n", dst.bands() - 1));
-    VImage dstAlpha = dst[dst.bands() - 1] * (1.0 / 255.0);
-
-    //
-    // Compute normalized output alpha channel:
-    //
-    // References:
-    // - http://en.wikipedia.org/wiki/Alpha_compositing#Alpha_blending
-    // - https://github.com/libvips/ruby-vips/issues/28#issuecomment-9014826
-    //
-    // out_a = src_a + dst_a * (1 - src_a)
-    //                         ^^^^^^^^^^^
-    //                            t0
-    VImage t0 = srcAlpha.linear(-1.0, 1.0);
-    VImage outAlphaNormalized = srcAlpha + dstAlpha * t0;
-
-    //
-    // Compute output RGB channels:
-    //
-    // Wikipedia:
-    // out_rgb = (src_rgb * src_a + dst_rgb * dst_a * (1 - src_a)) / out_a
-    //                                                ^^^^^^^^^^^
-    //                                                    t0
-    //
-    // Omit division by `out_a` since `Compose` is supposed to output a
-    // premultiplied RGBA image as reversal of premultiplication is handled
-    // externally.
-    //
-    VImage outRGBPremultiplied = srcWithoutAlpha + dstWithoutAlpha * t0;
-
-    // Combine RGB and alpha channel into output image:
-    return outRGBPremultiplied.bandjoin(outAlphaNormalized * 255.0);
-  }
-
-  /*
-    Cutout src over dst with given gravity.
-   */
-  VImage Cutout(VImage mask, VImage dst, const int gravity) {
-    using sharp::CalculateCrop;
-    using sharp::HasAlpha;
-    using sharp::MaximumImageAlpha;
-
-    bool maskHasAlpha = HasAlpha(mask);
-
-    if (!maskHasAlpha && mask.bands() > 1) {
-      throw VError("Overlay image must have an alpha channel or one band");
-    }
-    if (!HasAlpha(dst)) {
-      throw VError("Image to be overlaid must have an alpha channel");
-    }
-    if (mask.width() > dst.width() || mask.height() > dst.height()) {
-      throw VError("Overlay image must have same dimensions or smaller");
-    }
-
-    // Enlarge overlay mask, if required
-    if (mask.width() < dst.width() || mask.height() < dst.height()) {
-      // Calculate the (left, top) coordinates of the output image within the input image, applying the given gravity.
-      int left;
-      int top;
-      std::tie(left, top) = CalculateCrop(dst.width(), dst.height(), mask.width(), mask.height(), gravity);
-      // Embed onto transparent background
-      std::vector<double> background { 0.0, 0.0, 0.0, 0.0 };
-      mask = mask.embed(left, top, dst.width(), dst.height(), VImage::option()
-              ->set("extend", VIPS_EXTEND_BACKGROUND)
-              ->set("background", background));
-    }
-
-    // we use the mask alpha if it has alpha
-    if (maskHasAlpha) {
-      mask = mask.extract_band(mask.bands() - 1, VImage::option()->set("n", 1));;
-    }
-
-    // Split dst into an optional alpha
-    VImage dstAlpha = dst.extract_band(dst.bands() - 1, VImage::option()->set("n", 1));
-
-    // we use the dst non-alpha
-    dst = dst.extract_band(0, VImage::option()->set("n", dst.bands() - 1));
-
-    // the range of the mask and the image need to match .. one could be
-    // 16-bit, one 8-bit
-    double const dstMax = MaximumImageAlpha(dst.interpretation());
-    double const maskMax = MaximumImageAlpha(mask.interpretation());
-
-    // combine the new mask and the existing alpha ... there are
-    // many ways of doing this, mult is the simplest
-    mask = dstMax * ((mask / maskMax) * (dstAlpha / dstMax));
-
-    // append the mask to the image data ... the mask might be float now,
-    // we must cast the format down to match the image data
-    return dst.bandjoin(mask.cast(dst.format()));
-  }
-
   /*
    * Tint an image using the specified chroma, preserving the original image luminance
    */

src/operations.h

@@ -35,27 +35,6 @@ namespace sharp {
   */
   VImage EnsureAlpha(VImage image);
 
-  /*
-    Alpha composite src over dst with given gravity.
-    Assumes alpha channels are already premultiplied and will be unpremultiplied after.
-   */
-  VImage Composite(VImage src, VImage dst, const int gravity);
-
-  /*
-    Composite overlayImage over image at given position
-   */
-  VImage Composite(VImage image, VImage overlayImage, int const x, int const y);
-
-  /*
-    Alpha composite overlayImage over image, assumes matching dimensions
-  */
-  VImage AlphaComposite(VImage image, VImage overlayImage);
-
-  /*
-    Cutout src over dst with given gravity.
-  */
-  VImage Cutout(VImage src, VImage dst, const int gravity);
-
   /*
    * Tint an image using the specified chroma, preserving the original image luminance
    */

src/pipeline.cc

@@ -343,30 +343,19 @@ class PipelineWorker : public Nan::AsyncWorker {
         image = image.colourspace(VIPS_INTERPRETATION_B_W);
       }
 
-      // Ensure image has an alpha channel when there is an overlay with an alpha channel
-      VImage overlayImage;
-      ImageType overlayImageType = ImageType::UNKNOWN;
-      bool shouldOverlayWithAlpha = FALSE;
-      if (baton->overlay != nullptr) {
-        std::tie(overlayImage, overlayImageType) = OpenInput(baton->overlay, baton->accessMethod);
-        if (HasAlpha(overlayImage)) {
-          shouldOverlayWithAlpha = !baton->overlayCutout;
-          if (!HasAlpha(image)) {
-            double const multiplier = sharp::Is16Bit(image.interpretation()) ? 256.0 : 1.0;
-            image = image.bandjoin(
-              VImage::new_matrix(image.width(), image.height()).new_from_image(255 * multiplier));
-          }
-        }
-      }
-
       bool const shouldResize = xfactor != 1.0 || yfactor != 1.0;
       bool const shouldBlur = baton->blurSigma != 0.0;
       bool const shouldConv = baton->convKernelWidth * baton->convKernelHeight > 0;
       bool const shouldSharpen = baton->sharpenSigma != 0.0;
       bool const shouldApplyMedian = baton->medianSize > 0;
+      bool const shouldComposite = !baton->composite.empty();
+
+      if (shouldComposite && !HasAlpha(image)) {
+        image = sharp::EnsureAlpha(image);
+      }
 
       bool const shouldPremultiplyAlpha = HasAlpha(image) &&
-        (shouldResize || shouldBlur || shouldConv || shouldSharpen || shouldOverlayWithAlpha);
+        (shouldResize || shouldBlur || shouldConv || shouldSharpen || shouldComposite);
 
       // Premultiply image alpha channel before all transformations to avoid
       // dark fringing around bright pixels
@@ -544,72 +533,67 @@ class PipelineWorker : public Nan::AsyncWorker {
         image = sharp::Sharpen(image, baton->sharpenSigma, baton->sharpenFlat, baton->sharpenJagged);
       }
 
-      // Composite with overlay, if present
+      // Composite
-      if (baton->overlay != nullptr) {
+      if (shouldComposite) {
-        // Verify overlay image is within current dimensions
+        for (Composite *composite : baton->composite) {
-        if (overlayImage.width() > image.width() || overlayImage.height() > image.height()) {
+          VImage compositeImage;
-          throw vips::VError("Overlay image must have same dimensions or smaller");
+          ImageType compositeImageType = ImageType::UNKNOWN;
+          std::tie(compositeImage, compositeImageType) = OpenInput(composite->input, baton->accessMethod);
+          // Verify within current dimensions
+          if (compositeImage.width() > image.width() || compositeImage.height() > image.height()) {
+            throw vips::VError("Image to composite must have same dimensions or smaller");
           }
           // Check if overlay is tiled
-        if (baton->overlayTile) {
+          if (composite->tile) {
-          int const overlayImageWidth = overlayImage.width();
-          int const overlayImageHeight = overlayImage.height();
             int across = 0;
             int down = 0;
             // Use gravity in overlay
-          if (overlayImageWidth <= baton->width) {
+            if (compositeImage.width() <= baton->width) {
-            across = static_cast<int>(ceil(static_cast<double>(image.width()) / overlayImageWidth));
+              across = static_cast<int>(ceil(static_cast<double>(image.width()) / compositeImage.width()));
             }
-          if (overlayImageHeight <= baton->height) {
+            if (compositeImage.height() <= baton->height) {
-            down = static_cast<int>(ceil(static_cast<double>(image.height()) / overlayImageHeight));
+              down = static_cast<int>(ceil(static_cast<double>(image.height()) / compositeImage.height()));
             }
             if (across != 0 || down != 0) {
               int left;
               int top;
-            overlayImage = overlayImage.replicate(across, down);
+              compositeImage = compositeImage.replicate(across, down);
-            if (baton->overlayXOffset >= 0 && baton->overlayYOffset >= 0) {
+              if (composite->left >= 0 && composite->top >= 0) {
-              // the overlayX/YOffsets will now be used to CalculateCrop for extract_area
                 std::tie(left, top) = sharp::CalculateCrop(
-                overlayImage.width(), overlayImage.height(), image.width(), image.height(),
+                  compositeImage.width(), compositeImage.height(), image.width(), image.height(),
-                baton->overlayXOffset, baton->overlayYOffset);
+                  composite->left, composite->top);
               } else {
-              // the overlayGravity will now be used to CalculateCrop for extract_area
                 std::tie(left, top) = sharp::CalculateCrop(
-                overlayImage.width(), overlayImage.height(), image.width(), image.height(), baton->overlayGravity);
+                  compositeImage.width(), compositeImage.height(), image.width(), image.height(), composite->gravity);
               }
-            overlayImage = overlayImage.extract_area(left, top, image.width(), image.height());
+              compositeImage = compositeImage.extract_area(left, top, image.width(), image.height());
             }
-          // the overlayGravity was used for extract_area, therefore set it back to its default value of 0
+            // gravity was used for extract_area, set it back to its default value of 0
-          baton->overlayGravity = 0;
+            composite->gravity = 0;
           }
-        if (baton->overlayCutout) {
+          // Ensure image to composite is sRGB with premultiplied alpha
-          // 'cut out' the image, premultiplication is not required
+          compositeImage = compositeImage.colourspace(VIPS_INTERPRETATION_sRGB);
-          image = sharp::Cutout(overlayImage, image, baton->overlayGravity);
+          if (!HasAlpha(compositeImage)) {
-        } else {
+            compositeImage = sharp::EnsureAlpha(compositeImage);
-          // Ensure overlay is sRGB
-          overlayImage = overlayImage.colourspace(VIPS_INTERPRETATION_sRGB);
-          // Ensure overlay matches premultiplication state
-          if (shouldPremultiplyAlpha) {
-            // Ensure overlay has alpha channel
-            if (!HasAlpha(overlayImage)) {
-              double const multiplier = sharp::Is16Bit(overlayImage.interpretation()) ? 256.0 : 1.0;
-              overlayImage = overlayImage.bandjoin(
-                VImage::new_matrix(overlayImage.width(), overlayImage.height()).new_from_image(255 * multiplier));
-            }
-            overlayImage = overlayImage.premultiply();
           }
+          compositeImage = compositeImage.premultiply();
+          // Calculate position
           int left;
           int top;
-          if (baton->overlayXOffset >= 0 && baton->overlayYOffset >= 0) {
+          if (composite->left >= 0 && composite->top >= 0) {
-            // Composite images at given offsets
+            // Composite image at given offsets
             std::tie(left, top) = sharp::CalculateCrop(image.width(), image.height(),
-              overlayImage.width(), overlayImage.height(), baton->overlayXOffset, baton->overlayYOffset);
+              compositeImage.width(), compositeImage.height(), composite->left, composite->top);
           } else {
-            // Composite images with given gravity
+            // Composite image with given gravity
             std::tie(left, top) = sharp::CalculateCrop(image.width(), image.height(),
-              overlayImage.width(), overlayImage.height(), baton->overlayGravity);
+              compositeImage.width(), compositeImage.height(), composite->gravity);
           }
-          image = sharp::Composite(image, overlayImage, left, top);
+          // Composite
+          image = image.composite2(compositeImage, composite->mode, VImage::option()
+            ->set("premultiplied", TRUE)
+            ->set("x", left)
+            ->set("y", top));
         }
       }
 
@@ -1029,13 +1013,17 @@ class PipelineWorker : public Nan::AsyncWorker {
         GetFromPersistent(index);
         return index + 1;
       });
+
+    // Delete baton
     delete baton->input;
-    delete baton->overlay;
     delete baton->boolean;
-    for_each(baton->joinChannelIn.begin(), baton->joinChannelIn.end(),
+    for (Composite *composite : baton->composite) {
-      [this](sharp::InputDescriptor *joinChannelIn) {
+      delete composite->input;
-        delete joinChannelIn;
+      delete composite;
-      });
+    }
+    for (sharp::InputDescriptor *input : baton->joinChannelIn) {
+      delete input;
+    }
     delete baton;
 
     // Handle warnings
@@ -1182,14 +1170,21 @@ NAN_METHOD(pipeline) {
   // Tint chroma
   baton->tintA = AttrTo<double>(options, "tintA");
   baton->tintB = AttrTo<double>(options, "tintB");
-  // Overlay options
+  // Composite
-  if (HasAttr(options, "overlay")) {
+  v8::Local<v8::Array> compositeArray = Nan::Get(options, Nan::New("composite").ToLocalChecked())
-    baton->overlay = CreateInputDescriptor(AttrAs<v8::Object>(options, "overlay"), buffersToPersist);
+    .ToLocalChecked().As<v8::Array>();
-    baton->overlayGravity = AttrTo<int32_t>(options, "overlayGravity");
+  int const compositeArrayLength = AttrTo<uint32_t>(compositeArray, "length");
-    baton->overlayXOffset = AttrTo<int32_t>(options, "overlayXOffset");
+  for (int i = 0; i < compositeArrayLength; i++) {
-    baton->overlayYOffset = AttrTo<int32_t>(options, "overlayYOffset");
+    v8::Local<v8::Object> compositeObject = Nan::Get(compositeArray, i).ToLocalChecked().As<v8::Object>();
-    baton->overlayTile = AttrTo<bool>(options, "overlayTile");
+    Composite *composite = new Composite;
-    baton->overlayCutout = AttrTo<bool>(options, "overlayCutout");
+    composite->input = CreateInputDescriptor(AttrAs<v8::Object>(compositeObject, "input"), buffersToPersist);
+    composite->mode = static_cast<VipsBlendMode>(
+      vips_enum_from_nick(nullptr, VIPS_TYPE_BLEND_MODE, AttrAsStr(compositeObject, "blend").data()));
+    composite->gravity = AttrTo<uint32_t>(compositeObject, "gravity");
+    composite->left = AttrTo<int32_t>(compositeObject, "left");
+    composite->top = AttrTo<int32_t>(compositeObject, "top");
+    composite->tile = AttrTo<bool>(compositeObject, "tile");
+    baton->composite.push_back(composite);
   }
   // Resize options
   baton->withoutEnlargement = AttrTo<bool>(options, "withoutEnlargement");

src/pipeline.h

@@ -34,6 +34,23 @@ enum class Canvas {
   IGNORE_ASPECT
 };
 
+struct Composite {
+  sharp::InputDescriptor *input;
+  VipsBlendMode mode;
+  int gravity;
+  int left;
+  int top;
+  bool tile;
+
+  Composite():
+    input(nullptr),
+    mode(VIPS_BLEND_MODE_OVER),
+    gravity(0),
+    left(-1),
+    top(-1),
+    tile(false) {}
+};
+
 struct PipelineBaton {
   sharp::InputDescriptor *input;
   std::string iccProfilePath;
@@ -42,12 +59,7 @@ struct PipelineBaton {
   std::string fileOut;
   void *bufferOut;
   size_t bufferOutLength;
-  sharp::InputDescriptor *overlay;
+  std::vector<Composite *> composite;
-  int overlayGravity;
-  int overlayXOffset;
-  int overlayYOffset;
-  bool overlayTile;
-  bool overlayCutout;
   std::vector<sharp::InputDescriptor *> joinChannelIn;
   int topOffsetPre;
   int leftOffsetPre;
@@ -161,12 +173,6 @@ struct PipelineBaton {
     input(nullptr),
     limitInputPixels(0),
     bufferOutLength(0),
-    overlay(nullptr),
-    overlayGravity(0),
-    overlayXOffset(-1),
-    overlayYOffset(-1),
-    overlayTile(false),
-    overlayCutout(false),
     topOffsetPre(-1),
     topOffsetPost(-1),
     channels(0),

test/unit/composite.js

@@ -0,0 +1,298 @@
+'use strict';
+
+const assert = require('assert');
+
+const fixtures = require('../fixtures');
+const sharp = require('../../');
+
+const red = { r: 255, g: 0, b: 0, alpha: 0.5 };
+const green = { r: 0, g: 255, b: 0, alpha: 0.5 };
+const blue = { r: 0, g: 0, b: 255, alpha: 0.5 };
+
+const redRect = {
+  create: {
+    width: 80,
+    height: 60,
+    channels: 4,
+    background: red
+  }
+};
+
+const greenRect = {
+  create: {
+    width: 40,
+    height: 40,
+    channels: 4,
+    background: green
+  }
+};
+
+const blueRect = {
+  create: {
+    width: 60,
+    height: 40,
+    channels: 4,
+    background: blue
+  }
+};
+
+const blends = [
+  'over',
+  'xor',
+  'saturate',
+  'dest-over'
+];
+
+// Test
+describe('composite', () => {
+  it('blend', () => Promise.all(
+    blends.map(blend => {
+      const filename = `composite.blend.${blend}.png`;
+      const actual = fixtures.path(`output.${filename}`);
+      const expected = fixtures.expected(filename);
+      return sharp(redRect)
+        .composite([{
+          input: blueRect,
+          blend
+        }])
+        .toFile(actual)
+        .then(() => {
+          fixtures.assertMaxColourDistance(actual, expected);
+        });
+    })
+  ));
+
+  it('multiple', () => {
+    const filename = 'composite-multiple.png';
+    const actual = fixtures.path(`output.${filename}`);
+    const expected = fixtures.expected(filename);
+    return sharp(redRect)
+      .composite([{
+        input: blueRect,
+        gravity: 'northeast'
+      }, {
+        input: greenRect,
+        gravity: 'southwest'
+      }])
+      .toFile(actual)
+      .then(() => {
+        fixtures.assertMaxColourDistance(actual, expected);
+      });
+  });
+
+  it('zero offset', done => {
+    sharp(fixtures.inputJpg)
+      .resize(400)
+      .composite([{
+        input: fixtures.inputPngWithTransparency16bit,
+        top: 0,
+        left: 0
+      }])
+      .toBuffer((err, data, info) => {
+        if (err) throw err;
+        assert.strictEqual('jpeg', info.format);
+        assert.strictEqual(3, info.channels);
+        fixtures.assertSimilar(fixtures.expected('overlay-offset-0.jpg'), data, done);
+      });
+  });
+
+  it('offset and gravity', done => {
+    sharp(fixtures.inputJpg)
+      .resize(400)
+      .composite([{
+        input: fixtures.inputPngWithTransparency16bit,
+        left: 10,
+        top: 10,
+        gravity: 4
+      }])
+      .toBuffer((err, data, info) => {
+        if (err) throw err;
+        assert.strictEqual('jpeg', info.format);
+        assert.strictEqual(3, info.channels);
+        fixtures.assertSimilar(fixtures.expected('overlay-offset-with-gravity.jpg'), data, done);
+      });
+  });
+
+  it('offset, gravity and tile', done => {
+    sharp(fixtures.inputJpg)
+      .resize(400)
+      .composite([{
+        input: fixtures.inputPngWithTransparency16bit,
+        left: 10,
+        top: 10,
+        gravity: 4,
+        tile: true
+      }])
+      .toBuffer((err, data, info) => {
+        if (err) throw err;
+        assert.strictEqual('jpeg', info.format);
+        assert.strictEqual(3, info.channels);
+        fixtures.assertSimilar(fixtures.expected('overlay-offset-with-gravity-tile.jpg'), data, done);
+      });
+  });
+
+  it('offset and tile', done => {
+    sharp(fixtures.inputJpg)
+      .resize(400)
+      .composite([{
+        input: fixtures.inputPngWithTransparency16bit,
+        left: 10,
+        top: 10,
+        tile: true
+      }])
+      .toBuffer((err, data, info) => {
+        if (err) throw err;
+        assert.strictEqual('jpeg', info.format);
+        assert.strictEqual(3, info.channels);
+        fixtures.assertSimilar(fixtures.expected('overlay-offset-with-tile.jpg'), data, done);
+      });
+  });
+
+  it('cutout via dest-in', done => {
+    sharp(fixtures.inputJpg)
+      .resize(300, 300)
+      .composite([{
+        input: Buffer.from('<svg><rect x="0" y="0" width="200" height="200" rx="50" ry="50"/></svg>'),
+        density: 96,
+        blend: 'dest-in',
+        cutout: true
+      }])
+      .png()
+      .toBuffer((err, data, info) => {
+        if (err) throw err;
+        assert.strictEqual('png', info.format);
+        assert.strictEqual(300, info.width);
+        assert.strictEqual(300, info.height);
+        assert.strictEqual(4, info.channels);
+        fixtures.assertSimilar(fixtures.expected('composite-cutout.png'), data, done);
+      });
+  });
+
+  describe('numeric gravity', () => {
+    Object.keys(sharp.gravity).forEach(gravity => {
+      it(gravity, done => {
+        sharp(fixtures.inputJpg)
+          .resize(80)
+          .composite([{
+            input: fixtures.inputPngWithTransparency16bit,
+            gravity: gravity
+          }])
+          .toBuffer((err, data, info) => {
+            if (err) throw err;
+            assert.strictEqual('jpeg', info.format);
+            assert.strictEqual(80, info.width);
+            assert.strictEqual(65, info.height);
+            assert.strictEqual(3, info.channels);
+            fixtures.assertSimilar(fixtures.expected(`overlay-gravity-${gravity}.jpg`), data, done);
+          });
+      });
+    });
+  });
+
+  describe('string gravity', () => {
+    Object.keys(sharp.gravity).forEach(gravity => {
+      it(gravity, done => {
+        const expected = fixtures.expected('overlay-gravity-' + gravity + '.jpg');
+        sharp(fixtures.inputJpg)
+          .resize(80)
+          .composite([{
+            input: fixtures.inputPngWithTransparency16bit,
+            gravity: sharp.gravity[gravity]
+          }])
+          .toBuffer((err, data, info) => {
+            if (err) throw err;
+            assert.strictEqual('jpeg', info.format);
+            assert.strictEqual(80, info.width);
+            assert.strictEqual(65, info.height);
+            assert.strictEqual(3, info.channels);
+            fixtures.assertSimilar(expected, data, done);
+          });
+      });
+    });
+  });
+
+  describe('tile and gravity', () => {
+    Object.keys(sharp.gravity).forEach(gravity => {
+      it(gravity, done => {
+        const expected = fixtures.expected('overlay-tile-gravity-' + gravity + '.jpg');
+        sharp(fixtures.inputJpg)
+          .resize(80)
+          .composite([{
+            input: fixtures.inputPngWithTransparency16bit,
+            tile: true,
+            gravity: gravity
+          }])
+          .toBuffer((err, data, info) => {
+            if (err) throw err;
+            assert.strictEqual('jpeg', info.format);
+            assert.strictEqual(80, info.width);
+            assert.strictEqual(65, info.height);
+            assert.strictEqual(3, info.channels);
+            fixtures.assertSimilar(expected, data, done);
+          });
+      });
+    });
+  });
+
+  describe('validation', () => {
+    it('missing images', () => {
+      assert.throws(() => {
+        sharp().composite();
+      }, /Expected array for images to composite but received undefined of type undefined/);
+    });
+
+    it('invalid images', () => {
+      assert.throws(() => {
+        sharp().composite(['invalid']);
+      }, /Expected object for image to composite but received invalid of type string/);
+    });
+
+    it('missing input', () => {
+      assert.throws(() => {
+        sharp().composite([{}]);
+      }, /Unsupported input/);
+    });
+
+    it('invalid blend', () => {
+      assert.throws(() => {
+        sharp().composite([{ input: 'test', blend: 'invalid' }]);
+      }, /Expected valid blend name for blend but received invalid of type string/);
+    });
+
+    it('invalid tile', () => {
+      assert.throws(() => {
+        sharp().composite([{ input: 'test', tile: 'invalid' }]);
+      }, /Expected boolean for tile but received invalid of type string/);
+    });
+
+    it('invalid left', () => {
+      assert.throws(() => {
+        sharp().composite([{ input: 'test', left: 0.5 }]);
+      }, /Expected positive integer for left but received 0.5 of type number/);
+    });
+
+    it('invalid top', () => {
+      assert.throws(() => {
+        sharp().composite([{ input: 'test', top: -1 }]);
+      }, /Expected positive integer for top but received -1 of type number/);
+    });
+
+    it('left but no top', () => {
+      assert.throws(() => {
+        sharp().composite([{ input: 'test', left: 1 }]);
+      }, /Expected both left and top to be set/);
+    });
+
+    it('top but no left', () => {
+      assert.throws(() => {
+        sharp().composite([{ input: 'test', top: 1 }]);
+      }, /Expected both left and top to be set/);
+    });
+
+    it('invalid gravity', () => {
+      assert.throws(() => {
+        sharp().composite([{ input: 'test', gravity: 'invalid' }]);
+      }, /Expected valid gravity for gravity but received invalid of type string/);
+    });
+  });
+});

test/unit/overlay.js

@@ -140,7 +140,6 @@ describe('Overlays', function () {
       });
   });
 
-  if (sharp.format.webp.input.file) {
   it('Composite WebP onto JPEG', function (done) {
     const paths = getPaths('overlay-jpeg-with-webp', 'jpg');
 
@@ -153,24 +152,23 @@ describe('Overlays', function () {
         done();
       });
   });
-  }
 
-  it('Composite JPEG onto PNG, no premultiply', function (done) {
+  it('Composite JPEG onto PNG, ensure premultiply', function (done) {
     sharp(fixtures.inputPngOverlayLayer1)
       .overlayWith(fixtures.inputJpgWithLandscapeExif1)
       .toBuffer(function (err, data, info) {
         if (err) throw err;
-        assert.strictEqual(false, info.premultiplied);
+        assert.strictEqual(true, info.premultiplied);
         done();
       });
   });
 
-  it('Composite opaque JPEG onto JPEG, no premultiply', function (done) {
+  it('Composite opaque JPEG onto JPEG, ensure premultiply', function (done) {
     sharp(fixtures.inputJpg)
       .overlayWith(fixtures.inputJpgWithLandscapeExif1)
       .toBuffer(function (err, data, info) {
         if (err) throw err;
-        assert.strictEqual(false, info.premultiplied);
+        assert.strictEqual(true, info.premultiplied);
         done();
       });
   });
@@ -409,12 +407,6 @@ describe('Overlays', function () {
         });
     });
 
-    it('Overlay with invalid cutout option', function () {
-      assert.throws(function () {
-        sharp().overlayWith('ignore', { cutout: 1 });
-      });
-    });
-
     it('Overlay with invalid tile option', function () {
       assert.throws(function () {
         sharp().overlayWith('ignore', { tile: 1 });
@@ -580,18 +572,17 @@ describe('Overlays', function () {
       });
   });
 
-  it('Composite JPEG onto JPEG, no premultiply', function (done) {
+  it('Composite JPEG onto JPEG', function (done) {
     sharp(fixtures.inputJpg)
       .resize(480, 320)
       .overlayWith(fixtures.inputJpgBooleanTest)
-      .png()
       .toBuffer(function (err, data, info) {
         if (err) throw err;
-        assert.strictEqual('png', info.format);
+        assert.strictEqual('jpeg', info.format);
         assert.strictEqual(480, info.width);
         assert.strictEqual(320, info.height);
         assert.strictEqual(3, info.channels);
-        assert.strictEqual(false, info.premultiplied);
+        assert.strictEqual(true, info.premultiplied);
         fixtures.assertSimilar(fixtures.expected('overlay-jpeg-with-jpeg.jpg'), data, done);
       });
   });