Ensure images with P3 profiles retain full gamut #2862

docs/changelog.md

@@ -12,6 +12,9 @@ Requires libvips v8.11.3
 * Ensure background is always premultiplied when compositing.
   [#2858](https://github.com/lovell/sharp/issues/2858)
 
+* Ensure images with P3 profiles retain full gamut.
+  [#2862](https://github.com/lovell/sharp/issues/2862)
+
 ### v0.29.0 - 17th August 2021
 
 * Drop support for Node.js 10, now requires Node.js >= 12.13.0.

src/pipeline.cc

@@ -291,14 +291,15 @@ class PipelineWorker : public Napi::AsyncWorker {
       }
 
       // Ensure we're using a device-independent colour space
+      char const *processingProfile = image.interpretation() == VIPS_INTERPRETATION_RGB16 ? "p3" : "srgb";
       if (
         sharp::HasProfile(image) &&
         image.interpretation() != VIPS_INTERPRETATION_LABS &&
         image.interpretation() != VIPS_INTERPRETATION_GREY16
       ) {
-        // Convert to sRGB using embedded profile
+        // Convert to sRGB/P3 using embedded profile
         try {
-          image = image.icc_transform("srgb", VImage::option()
+          image = image.icc_transform(processingProfile, VImage::option()
             ->set("embedded", TRUE)
             ->set("depth", image.interpretation() == VIPS_INTERPRETATION_RGB16 ? 16 : 8)
             ->set("intent", VIPS_INTENT_PERCEPTUAL));
@@ -306,7 +307,7 @@ class PipelineWorker : public Napi::AsyncWorker {
           // Ignore failure of embedded profile
         }
       } else if (image.interpretation() == VIPS_INTERPRETATION_CMYK) {
-        image = image.icc_transform("srgb", VImage::option()
+        image = image.icc_transform(processingProfile, VImage::option()
           ->set("input_profile", "cmyk")
           ->set("intent", VIPS_INTENT_PERCEPTUAL));
       }
@@ -715,9 +716,10 @@ class PipelineWorker : public Napi::AsyncWorker {
         // Convert colourspace, pass the current known interpretation so libvips doesn't have to guess
         image = image.colourspace(baton->colourspace, VImage::option()->set("source_space", image.interpretation()));
         // Transform colours from embedded profile to output profile
-        if (baton->withMetadata && sharp::HasProfile(image)) {
-          image = image.icc_transform(vips_enum_nick(VIPS_TYPE_INTERPRETATION, baton->colourspace),
-            VImage::option()->set("embedded", TRUE));
+        if (baton->withMetadata && sharp::HasProfile(image) && baton->withMetadataIcc.empty()) {
+          image = image.icc_transform("srgb", VImage::option()
+            ->set("embedded", TRUE)
+            ->set("intent", VIPS_INTENT_PERCEPTUAL));
         }
       }
 
@@ -726,7 +728,8 @@ class PipelineWorker : public Napi::AsyncWorker {
         image = image.icc_transform(
           const_cast<char*>(baton->withMetadataIcc.data()),
           VImage::option()
-            ->set("input_profile", "srgb")
+            ->set("input_profile", processingProfile)
+            ->set("embedded", TRUE)
             ->set("intent", VIPS_INTENT_PERCEPTUAL));
       }
       // Override EXIF Orientation tag

test/fixtures/index.js

@@ -92,6 +92,7 @@ module.exports = {
   inputPngRGBWithAlpha: getPath('2569067123_aca715a2ee_o.png'), // http://www.flickr.com/photos/grizdave/2569067123/ (same as inputJpg)
   inputPngImageInAlpha: getPath('image-in-alpha.png'), // https://github.com/lovell/sharp/issues/1597
   inputPngSolidAlpha: getPath('with-alpha.png'), // https://github.com/lovell/sharp/issues/1599
+  inputPngP3: getPath('p3.png'), // https://github.com/lovell/sharp/issues/2862
 
   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/colourspace.js

@@ -105,6 +105,25 @@ describe('Colour space conversion', function () {
       });
   });
 
+  it('Convert P3 to sRGB', async () => {
+    const [r, g, b] = await sharp(fixtures.inputPngP3)
+      .raw()
+      .toBuffer();
+    assert.strictEqual(r, 255);
+    assert.strictEqual(g, 0);
+    assert.strictEqual(b, 0);
+  });
+
+  it('Passthrough P3', async () => {
+    const [r, g, b] = await sharp(fixtures.inputPngP3)
+      .withMetadata({ icc: 'p3' })
+      .raw()
+      .toBuffer();
+    assert.strictEqual(r, 234);
+    assert.strictEqual(g, 51);
+    assert.strictEqual(b, 34);
+  });
+
   it('Invalid pipelineColourspace input', function () {
     assert.throws(function () {
       sharp(fixtures.inputJpg)