Add pipelineColourspace operator

docs/api-colour.md

@@ -40,6 +40,51 @@ Alternative spelling of `greyscale`.
 
 Returns **Sharp** 
 
+## pipelineColourspace
+
+Set the pipeline colourspace.
+
+The input image will be converted to the provided colourspace at the start of the pipeline.
+All operations will use this colourspace before converting to the output colourspace, as defined by [toColourspace][6].
+
+This feature is experimental and has not yet been fully-tested with all operations.
+
+### Parameters
+
+*   `colourspace` **[string][1]?** pipeline colourspace e.g. `rgb16`, `scrgb`, `lab`, `grey16` [...][7]
+
+### Examples
+
+```javascript
+// Run pipeline in 16 bits per channel RGB while converting final result to 8 bits per channel sRGB.
+await sharp(input)
+ .pipelineColourspace('rgb16')
+ .toColourspace('srgb')
+ .toFile('16bpc-pipeline-to-8bpc-output.png')
+```
+
+*   Throws **[Error][4]** Invalid parameters
+
+Returns **Sharp** 
+
+**Meta**
+
+*   **since**: 0.29.0
+
+## pipelineColorspace
+
+Alternative spelling of `pipelineColourspace`.
+
+### Parameters
+
+*   `colorspace` **[string][1]?** pipeline colorspace.
+
+<!---->
+
+*   Throws **[Error][4]** Invalid parameters
+
+Returns **Sharp** 
+
 ## toColourspace
 
 Set the output colourspace.
@@ -47,7 +92,7 @@ By default output image will be web-friendly sRGB, with additional channels inte
 
 ### Parameters
 
-*   `colourspace` **[string][1]?** output colourspace e.g. `srgb`, `rgb`, `cmyk`, `lab`, `b-w` [...][6]
+*   `colourspace` **[string][1]?** output colourspace e.g. `srgb`, `rgb`, `cmyk`, `lab`, `b-w` [...][8]
 
 ### Examples
 
@@ -86,4 +131,8 @@ Returns **Sharp**
 
 [5]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean
 
-[6]: https://github.com/libvips/libvips/blob/3c0bfdf74ce1dc37a6429bed47fa76f16e2cd70a/libvips/iofuncs/enumtypes.c#L777-L794
+[6]: #tocolourspace
+
+[7]: https://github.com/libvips/libvips/blob/41cff4e9d0838498487a00623462204eb10ee5b8/libvips/iofuncs/enumtypes.c#L774
+
+[8]: https://github.com/libvips/libvips/blob/3c0bfdf74ce1dc37a6429bed47fa76f16e2cd70a/libvips/iofuncs/enumtypes.c#L777-L794

lib/colour.js

@@ -54,6 +54,45 @@ function grayscale (grayscale) {
   return this.greyscale(grayscale);
 }
 
+/**
+ * Set the pipeline colourspace.
+ *
+ * The input image will be converted to the provided colourspace at the start of the pipeline.
+ * All operations will use this colourspace before converting to the output colourspace, as defined by {@link toColourspace}.
+ *
+ * This feature is experimental and has not yet been fully-tested with all operations.
+ *
+ * @since 0.29.0
+ *
+ * @example
+ * // Run pipeline in 16 bits per channel RGB while converting final result to 8 bits per channel sRGB.
+ * await sharp(input)
+ *  .pipelineColourspace('rgb16')
+ *  .toColourspace('srgb')
+ *  .toFile('16bpc-pipeline-to-8bpc-output.png')
+ *
+ * @param {string} [colourspace] - pipeline colourspace e.g. `rgb16`, `scrgb`, `lab`, `grey16` [...](https://github.com/libvips/libvips/blob/41cff4e9d0838498487a00623462204eb10ee5b8/libvips/iofuncs/enumtypes.c#L774)
+ * @returns {Sharp}
+ * @throws {Error} Invalid parameters
+ */
+function pipelineColourspace (colourspace) {
+  if (!is.string(colourspace)) {
+    throw is.invalidParameterError('colourspace', 'string', colourspace);
+  }
+  this.options.colourspaceInput = colourspace;
+  return this;
+}
+
+/**
+ * Alternative spelling of `pipelineColourspace`.
+ * @param {string} [colorspace] - pipeline colorspace.
+ * @returns {Sharp}
+ * @throws {Error} Invalid parameters
+ */
+function pipelineColorspace (colorspace) {
+  return this.pipelineColourspace(colorspace);
+}
+
 /**
  * Set the output colourspace.
  * By default output image will be web-friendly sRGB, with additional channels interpreted as alpha channels.
@@ -119,6 +158,8 @@ module.exports = function (Sharp) {
     tint,
     greyscale,
     grayscale,
+    pipelineColourspace,
+    pipelineColorspace,
     toColourspace,
     toColorspace,
     // Private

lib/constructor.js

@@ -204,6 +204,7 @@ const Sharp = function (input, options) {
     removeAlpha: false,
     ensureAlpha: -1,
     colourspace: 'srgb',
+    colourspaceInput: 'last',
     composite: [],
     // output
     fileOut: '',

src/pipeline.cc

@@ -68,6 +68,13 @@ class PipelineWorker : public Napi::AsyncWorker {
       sharp::ImageType inputImageType;
       std::tie(image, inputImageType) = sharp::OpenInput(baton->input);
 
+      if (baton->colourspaceInput != VIPS_INTERPRETATION_LAST) {
+        if (image.interpretation() != baton->colourspaceInput) {
+          image = image.colourspace(baton->colourspaceInput,
+            VImage::option()->set("source_space", image.interpretation()));
+        }
+      }
+
       // Calculate angle of rotation
       VipsAngle rotation;
       if (baton->useExifOrientation) {
@@ -214,7 +221,7 @@ class PipelineWorker : public Napi::AsyncWorker {
       double yresidual = static_cast<double>(yshrink) / yfactor;
 
       // If integral x and y shrink are equal, try to use shrink-on-load for JPEG and WebP,
-      // but not when applying gamma correction, pre-resize extract or trim
+      // but not when applying gamma correction, pre-resize extract, trim or input colourspace
       int shrink_on_load = 1;
 
       int shrink_on_load_factor = 1;
@@ -227,6 +234,7 @@ class PipelineWorker : public Napi::AsyncWorker {
         xshrink == yshrink && xshrink >= 2 * shrink_on_load_factor &&
         (inputImageType == sharp::ImageType::JPEG || inputImageType == sharp::ImageType::WEBP) &&
         baton->gamma == 0 && baton->topOffsetPre == -1 && baton->trimThreshold == 0.0 &&
+        baton->colourspaceInput == VIPS_INTERPRETATION_LAST &&
         image.width() > 3 && image.height() > 3 && baton->input->pages == 1
       ) {
         if (xshrink >= 8 * shrink_on_load_factor) {
@@ -1385,6 +1393,10 @@ Napi::Value pipeline(const Napi::CallbackInfo& info) {
        baton->recombMatrix[i] = sharp::AttrAsDouble(recombMatrix, i);
     }
   }
+  baton->colourspaceInput = sharp::GetInterpretation(sharp::AttrAsStr(options, "colourspaceInput"));
+  if (baton->colourspaceInput == VIPS_INTERPRETATION_ERROR) {
+    baton->colourspaceInput = VIPS_INTERPRETATION_LAST;
+  }
   baton->colourspace = sharp::GetInterpretation(sharp::AttrAsStr(options, "colourspace"));
   if (baton->colourspace == VIPS_INTERPRETATION_ERROR) {
     baton->colourspace = VIPS_INTERPRETATION_sRGB;

src/pipeline.h

@@ -185,6 +185,7 @@ struct PipelineBaton {
   int extractChannel;
   bool removeAlpha;
   double ensureAlpha;
+  VipsInterpretation colourspaceInput;
   VipsInterpretation colourspace;
   int pageHeight;
   std::vector<int> delay;
@@ -308,6 +309,7 @@ struct PipelineBaton {
     extractChannel(-1),
     removeAlpha(false),
     ensureAlpha(-1.0),
+    colourspaceInput(VIPS_INTERPRETATION_LAST),
     colourspace(VIPS_INTERPRETATION_LAST),
     pageHeight(0),
     delay{-1},

test/fixtures/index.js

@@ -74,6 +74,7 @@ module.exports = {
   inputJpgLossless: getPath('testimgl.jpg'), // Lossless JPEG from ftp://ftp.fu-berlin.de/unix/X11/graphics/ImageMagick/delegates/ljpeg-6b.tar.gz
 
   inputPng: getPath('50020484-00001.png'), // http://c.searspartsdirect.com/lis_png/PLDM/50020484-00001.png
+  inputPngGradients: getPath('gradients-rgb8.png'),
   inputPngWithTransparency: getPath('blackbug.png'), // public domain
   inputPngCompleteTransparency: getPath('full-transparent.png'),
   inputPngWithGreyAlpha: getPath('grey-8bit-alpha.png'),

test/unit/colourspace.js

@@ -90,7 +90,29 @@ describe('Colour space conversion', function () {
       });
   });
 
-  it('Invalid input', function () {
+  it('From sRGB with RGB16 pipeline, resize with gamma, to sRGB', function (done) {
+    sharp(fixtures.inputPngGradients)
+      .pipelineColourspace('rgb16')
+      .resize(320)
+      .gamma()
+      .toColourspace('srgb')
+      .toBuffer(function (err, data, info) {
+        if (err) throw err;
+        assert.strictEqual(320, info.width);
+        fixtures.assertSimilar(fixtures.expected('colourspace-gradients-gamma-resize.png'), data, {
+          threshold: 0
+        }, done);
+      });
+  });
+
+  it('Invalid pipelineColourspace input', function () {
+    assert.throws(function () {
+      sharp(fixtures.inputJpg)
+        .pipelineColorspace(null);
+    }, /Expected string for colourspace but received null of type object/);
+  });
+
+  it('Invalid toColourspace input', function () {
     assert.throws(function () {
       sharp(fixtures.inputJpg)
         .toColourspace(null);