Add joinChannel and toColourspace commands

docs/api.md

@@ -60,7 +60,7 @@ Fast access to image metadata without decoding any compressed image data.
 * `format`: Name of decoder used to decompress image data e.g. `jpeg`, `png`, `webp`, `gif`, `svg`
 * `width`: Number of pixels wide
 * `height`: Number of pixels high
-* `space`: Name of colour space interpretation e.g. `srgb`, `rgb`, `scrgb`, `cmyk`, `lab`, `xyz`, `b-w` [...](https://github.com/jcupitt/libvips/blob/master/libvips/iofuncs/enumtypes.c#L522)
+* `space`: Name of colour space interpretation e.g. `srgb`, `rgb`, `scrgb`, `cmyk`, `lab`, `xyz`, `b-w` [...](https://github.com/jcupitt/libvips/blob/master/libvips/iofuncs/enumtypes.c#L568)
 * `channels`: Number of bands e.g. `3` for sRGB, `4` for CMYK
 * `density`: Number of pixels per inch (DPI), if present
 * `hasProfile`: Boolean indicating the presence of an embedded ICC profile
@@ -445,7 +445,7 @@ Convert to 8-bit greyscale; 256 shades of grey.
 
 This is a linear operation. If the input image is in a non-linear colour space such as sRGB, use `gamma()` with `greyscale()` for the best results.
 
-The output image will still be web-friendly sRGB and contain three (identical) channels.
+By default the output image will be web-friendly sRGB and contain three (identical) color channels. This may be overridden by other sharp operations such as `toColourspace('b-w')`, which will produce an output image containing one color channel. An alpha channel may be present, and will be unchanged by the operation.
 
 #### normalize() / normalise()
 
@@ -490,11 +490,17 @@ sharp('input.png')
   });
 ```
 
+#### toColourspace(colourspace) / toColorspace(colorspace)
+
+Set the output colourspace. By default output image will be web-friendly sRGB, with additional channels interpreted as alpha channels.  
+
+`colourspace` is a string or `sharp.colourspace` enum that identifies an output colourspace. String arguments comprise vips colour space interpretation names  e.g. `srgb`, `rgb`, `scrgb`, `cmyk`, `lab`, `xyz`, `b-w` [...](https://github.com/jcupitt/libvips/blob/master/libvips/iofuncs/enumtypes.c#L568)
+
 #### extractChannel(channel)
 
 Extract a single channel from a multi-channel image.
 
-* `channel` is a zero-indexed integral Number representing the band number to extract. `red`, `green` or `blue` are also accepted as an alternative to `0`, `1` or `2` respectively.
+`channel` is a zero-indexed integral Number representing the band number to extract. `red`, `green` or `blue` are also accepted as an alternative to `0`, `1` or `2` respectively.
 
 ```javascript
 sharp(input)
@@ -505,6 +511,22 @@ sharp(input)
    });
 ```
 
+#### joinChannel(channels, [options])
+
+Join a data channel to the image. The meaning of the added channels depends on the output colourspace, set with `toColourspace()`. By default the output image will be web-friendly sRGB, with additional channels interpreted as alpha channels.
+
+`channels` is one of
+* a single file path
+* an array of file paths
+* a single buffer
+* an array of buffers
+
+Note that channel ordering follows vips convention:
+* sRGB: 0: Red, 1: Green, 2: Blue, 3: Alpha
+* CMYK: 0: Magenta, 1: Cyan, 2: Yellow, 3: Black, 4: Alpha
+
+Buffers may be any of the image formats supported by sharp: JPEG, PNG, WebP, GIF, SVG, TIFF or raw pixel image data. In the case of a RAW buffer, the `options` object should contain a `raw` attribute, which follows the format of the attribute of the same name in the `sharp()` constructor. See `sharp()` for details. See `raw()` for pixel ordering. 
+
 #### bandbool(operation)
 
 Perform a bitwise boolean operation on all input image channels (bands) to produce a single channel output image.

index.js

@@ -86,6 +86,7 @@ var Sharp = function(input, options) {
     normalize: 0,
     booleanBufferIn: null,
     booleanFileIn: '',
+    joinChannelIn: [],
     // overlay
     overlayGravity: 0,
     overlayXOffset : -1,
@@ -109,6 +110,7 @@ var Sharp = function(input, options) {
     tileSize: 256,
     tileOverlap: 0,
     extractChannel: -1,
+    colourspace: 'srgb',
     // Function to notify of queue length changes
     queueListener: function(queueLength) {
       module.exports.queue.emit('change', queueLength);
@@ -421,6 +423,20 @@ Sharp.prototype.overlayWith = function(overlay, options) {
   return this;
 };
 
+/*
+  Add another color channel to the image
+*/
+Sharp.prototype.joinChannel = function(images, options) {
+  if (Array.isArray(images)) {
+    images.forEach(function(image, index) {
+      this.options.joinChannelIn[index] = this._createInputDescriptor(image, options);
+    }, this);
+  } else {
+    this.options.joinChannelIn.push(this._createInputDescriptor(images, options));
+  }
+  return this;
+};
+
 /*
   Rotate output image by 0, 90, 180 or 270 degrees
   Auto-rotation based on the EXIF Orientation tag is represented by an angle of -1
@@ -629,6 +645,18 @@ Sharp.prototype.greyscale = function(greyscale) {
 };
 Sharp.prototype.grayscale = Sharp.prototype.greyscale;
 
+/*
+  Set output colourspace
+*/
+Sharp.prototype.toColourspace = function(colourspace) {
+  if (!isString(colourspace) ) {
+    throw new Error('Invalid output colourspace ' + colourspace);
+  }
+  this.options.colourspace = colourspace;
+  return this;
+};
+Sharp.prototype.toColorspace = Sharp.prototype.toColourspace;
+
 Sharp.prototype.progressive = function(progressive) {
   this.options.progressive = isBoolean(progressive) ? progressive : true;
   return this;
@@ -817,6 +845,15 @@ module.exports.bool = {
   or: 'or',
   eor: 'eor'
 };
+// Colourspaces
+module.exports.colourspace = {
+  multiband: 'multiband',
+  'b-w': 'b-w',
+  bw: 'b-w',
+  cmyk: 'cmyk',
+  srgb: 'srgb'
+};
+module.exports.colorspace = module.exports.colourspace;
 
 /*
   Resize image to width x height pixels

src/common.cc

@@ -430,4 +430,13 @@ namespace sharp {
     );
   }
 
+  /*
+    Get interpretation type from string
+  */
+  VipsInterpretation GetInterpretation(std::string const typeStr) {
+    return static_cast<VipsInterpretation>(
+      vips_enum_from_nick(nullptr, VIPS_TYPE_INTERPRETATION, typeStr.data())
+    );
+  }
+
 }  // namespace sharp

src/common.h

@@ -196,6 +196,11 @@ namespace sharp {
   */
   VipsOperationBoolean GetBooleanOperation(std::string const opStr);
 
+  /*
+    Get interpretation type from string
+  */
+  VipsInterpretation GetInterpretation(std::string const typeStr);
+
 }  // namespace sharp
 
 #endif  // SRC_COMMON_H_

src/pipeline.cc

@@ -4,6 +4,7 @@
 #include <utility>
 #include <memory>
 #include <numeric>
+#include <map>
 
 #include <vips/vips8>
 #include <node.h>
@@ -39,8 +40,15 @@ class PipelineWorker : public Nan::AsyncWorker {
     // Increment processing task counter
     g_atomic_int_inc(&sharp::counterProcess);
 
+    std::map<VipsInterpretation, std::string> profileMap;
     // Default sRGB ICC profile from https://packages.debian.org/sid/all/icc-profiles-free/filelist
-    std::string srgbProfile = baton->iccProfilePath + "sRGB.icc";
+    profileMap.insert(
+      std::pair<VipsInterpretation, std::string>(VIPS_INTERPRETATION_sRGB,
+                                                 baton->iccProfilePath + "sRGB.icc"));
+    // Convert to sRGB using default CMYK profile from http://www.argyllcms.com/cmyk.icm
+    profileMap.insert(
+      std::pair<VipsInterpretation, std::string>(VIPS_INTERPRETATION_CMYK,
+                                                 baton->iccProfilePath + "cmyk.icm"));
 
     try {
       // Open input
@@ -266,18 +274,18 @@ class PipelineWorker : public Nan::AsyncWorker {
       if (sharp::HasProfile(image)) {
         // Convert to sRGB using embedded profile
         try {
-          image = image.icc_transform(const_cast<char*>(srgbProfile.data()), VImage::option()
+          image = image.icc_transform(
+            const_cast<char*>(profileMap[VIPS_INTERPRETATION_sRGB].data()), VImage::option()
             ->set("embedded", TRUE)
             ->set("intent", VIPS_INTENT_PERCEPTUAL)
           );
         } catch(...) {
           // Ignore failure of embedded profile
         }
       } else if (image.interpretation() == VIPS_INTERPRETATION_CMYK) {
-        // Convert to sRGB using default CMYK profile from http://www.argyllcms.com/cmyk.icm
-        std::string cmykProfile = baton->iccProfilePath + "cmyk.icm";
-        image = image.icc_transform(const_cast<char*>(srgbProfile.data()), VImage::option()
-          ->set("input_profile", cmykProfile.data())
+        image = image.icc_transform(
+          const_cast<char*>(profileMap[VIPS_INTERPRETATION_sRGB].data()), VImage::option()
+          ->set("input_profile", profileMap[VIPS_INTERPRETATION_CMYK].data())
           ->set("intent", VIPS_INTENT_PERCEPTUAL)
         );
       }
@@ -420,6 +428,19 @@ class PipelineWorker : public Nan::AsyncWorker {
         sharp::RemoveExifOrientation(image);
       }
 
+      // Join additional color channels to the image
+      if(baton->joinChannelIn.size() > 0) {
+        VImage joinImage;
+        ImageType joinImageType = ImageType::UNKNOWN;
+
+        for(unsigned int i = 0; i < baton->joinChannelIn.size(); i++) {
+          std::tie(joinImage, joinImageType) = sharp::OpenInput(baton->joinChannelIn[i], baton->accessMethod);
+
+          image = image.bandjoin(joinImage);
+          image = image.copy(VImage::option()->set("interpretation", baton->colourspace));
+        }
+      }
+
       // Crop/embed
       if (image.width() != baton->width || image.height() != baton->height) {
         if (baton->canvas == Canvas::EMBED) {
@@ -654,12 +675,15 @@ class PipelineWorker : public Nan::AsyncWorker {
       if (sharp::Is16Bit(image.interpretation())) {
         image = image.cast(VIPS_FORMAT_USHORT);
       }
-      if (image.interpretation() != VIPS_INTERPRETATION_sRGB) {
-        image = image.colourspace(VIPS_INTERPRETATION_sRGB);
-        // Transform colours from embedded profile to sRGB profile
-        if (baton->withMetadata && sharp::HasProfile(image)) {
-          image = image.icc_transform(const_cast<char*>(srgbProfile.data()), VImage::option()
-            ->set("embedded", TRUE)
+      if (image.interpretation() != baton->colourspace) {
+        // Need to convert image
+        image = image.colourspace(baton->colourspace);
+        // Transform colours from embedded profile to output profile
+        if (baton->withMetadata &&
+            sharp::HasProfile(image) &&
+            profileMap[baton->colourspace] != std::string()) {
+          image = image.icc_transform(const_cast<char*>(profileMap[baton->colourspace].data()),
+            VImage::option()->set("embedded", TRUE)
           );
         }
       }
@@ -693,7 +717,11 @@ class PipelineWorker : public Nan::AsyncWorker {
           area->free_fn = nullptr;
           vips_area_unref(area);
           baton->formatOut = "jpeg";
-          baton->channels = std::min(baton->channels, 3);
+          if(baton->colourspace == VIPS_INTERPRETATION_CMYK) {
+            baton->channels = std::min(baton->channels, 4);
+          } else {
+            baton->channels = std::min(baton->channels, 3);
+          }
         } else if (baton->formatOut == "png" || (baton->formatOut == "input" && inputImageType == ImageType::PNG)) {
           // Strip profile
           if (!baton->withMetadata) {
@@ -1021,6 +1049,19 @@ NAN_METHOD(pipeline) {
   baton->crop = AttrTo<int32_t>(options, "crop");
   baton->kernel = AttrAsStr(options, "kernel");
   baton->interpolator = AttrAsStr(options, "interpolator");
+  // Join Channel Options
+  if(HasAttr(options, "joinChannelIn")) {
+    v8::Local<v8::Object> joinChannelObject = Nan::Get(options, Nan::New("joinChannelIn").ToLocalChecked())
+      .ToLocalChecked().As<v8::Object>();
+    v8::Local<v8::Array> joinChannelArray = joinChannelObject.As<v8::Array>();
+    int joinChannelArrayLength = AttrTo<int32_t>(joinChannelObject, "length");
+    for(int i = 0; i < joinChannelArrayLength; i++) {
+      baton->joinChannelIn.push_back(
+        CreateInputDescriptor(
+          Nan::Get(joinChannelArray, i).ToLocalChecked().As<v8::Object>(),
+          buffersToPersist));
+    }
+  }
   // Operators
   baton->flatten = AttrTo<bool>(options, "flatten");
   baton->negate = AttrTo<bool>(options, "negate");
@@ -1077,6 +1118,9 @@ NAN_METHOD(pipeline) {
   baton->optimiseScans = AttrTo<bool>(options, "optimiseScans");
   baton->withMetadata = AttrTo<bool>(options, "withMetadata");
   baton->withMetadataOrientation = AttrTo<uint32_t>(options, "withMetadataOrientation");
+  baton->colourspace = sharp::GetInterpretation(AttrAsStr(options, "colourspace"));
+  if(baton->colourspace == VIPS_INTERPRETATION_ERROR)
+    baton->colourspace = VIPS_INTERPRETATION_sRGB;
   // Output
   baton->formatOut = AttrAsStr(options, "formatOut");
   baton->fileOut = AttrAsStr(options, "fileOut");

src/pipeline.h

@@ -32,6 +32,7 @@ struct PipelineBaton {
   int overlayYOffset;
   bool overlayTile;
   bool overlayCutout;
+  std::vector<sharp::InputDescriptor *> joinChannelIn;
   int topOffsetPre;
   int leftOffsetPre;
   int widthPre;
@@ -90,6 +91,7 @@ struct PipelineBaton {
   VipsOperationBoolean booleanOp;
   VipsOperationBoolean bandBoolOp;
   int extractChannel;
+  VipsInterpretation colourspace;
   int tileSize;
   int tileOverlap;
   VipsForeignDzContainer tileContainer;
@@ -148,6 +150,7 @@ struct PipelineBaton {
     booleanOp(VIPS_OPERATION_BOOLEAN_LAST),
     bandBoolOp(VIPS_OPERATION_BOOLEAN_LAST),
     extractChannel(-1),
+    colourspace(VIPS_INTERPRETATION_LAST),
     tileSize(256),
     tileOverlap(0),
     tileContainer(VIPS_FOREIGN_DZ_CONTAINER_FS),

test/fixtures/index.js

@@ -80,6 +80,7 @@ module.exports = {
   inputPngAlphaPremultiplicationSmall: getPath('alpha-premultiply-1024x768-paper.png'),
   inputPngAlphaPremultiplicationLarge: getPath('alpha-premultiply-2048x1536-paper.png'),
   inputPngBooleanNoAlpha: getPath('bandbool.png'),
+  inputPngTestJoinChannel: getPath('testJoinChannel.png'),
 
   inputWebP: getPath('4.webp'), // http://www.gstatic.com/webp/gallery/4.webp
   inputWebPWithTransparency: getPath('5_webp_a.webp'), // http://www.gstatic.com/webp/gallery3/5_webp_a.webp

test/unit/bandbool.js

@@ -15,13 +15,12 @@ describe('Bandbool per-channel boolean operations', function() {
     it(op + ' operation', function(done) {
       sharp(fixtures.inputPngBooleanNoAlpha)
         .bandbool(op)
+        .toColourspace('b-w')
         .toBuffer(function(err, data, info) {
-          // should use .toColourspace('b-w') here to get 1 channel output, when it is merged
           if (err) throw err;
           assert.strictEqual(200, info.width);
           assert.strictEqual(200, info.height);
-          //assert.strictEqual(1, info.channels);
-          assert.strictEqual(3, info.channels);
+          assert.strictEqual(1, info.channels);
           fixtures.assertSimilar(fixtures.expected('bandbool_' + op + '_result.png'), data, done);
         });
     });

test/unit/colourspace.js

@@ -29,6 +29,20 @@ describe('Colour space conversion', function() {
       .toFile(fixtures.path('output.greyscale-not.jpg'), done);
   });
 
+  it('Greyscale with single channel output', function(done) {
+    sharp(fixtures.inputJpg)
+      .resize(320, 240)
+      .greyscale()
+      .toColourspace('b-w')
+      .toBuffer(function(err, data, info) {
+        if (err) throw err;
+        assert.strictEqual(1, info.channels);
+        assert.strictEqual(320, info.width);
+        assert.strictEqual(240, info.height);
+        fixtures.assertSimilar(fixtures.expected('output.greyscale-single.jpg'), data, done);
+      });
+  });
+
   if (sharp.format.tiff.input.file && sharp.format.webp.output.buffer) {
     it('From 1-bit TIFF to sRGB WebP [slow]', function(done) {
       sharp(fixtures.inputTiff)
@@ -79,4 +93,10 @@ describe('Colour space conversion', function() {
       });
   });
 
+  it('Invalid input', function() {
+    assert.throws(function() {
+      sharp(fixtures.inputJpg)
+        .toColourspace(null);
+    });
+  });
 });