Add some plumbing for the color management of canvases

third_party/WebKit/Source/core/html/canvas/CanvasRenderingContext.cpp

 /*
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 11 matching lines @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "core/html/canvas/CanvasRenderingContext.h"
 
 #include "core/html/canvas/CanvasImageSource.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/weborigin/SecurityOrigin.h"
 
+const char * const kLinearRGBCanvasColorSpaceName = "linear-rgb";
+const char * const kSRGBCanvasColorSpaceName = "srgb";
+const char * const kLegacyCanvasColorSpaceName = "legacy-srgb";
+
 namespace blink {
 
-CanvasRenderingContext::CanvasRenderingContext(HTMLCanvasElement* canvas, OffscreenCanvas* offscreenCanvas)
+CanvasRenderingContext::CanvasRenderingContext(HTMLCanvasElement* canvas, OffscreenCanvas* offscreenCanvas, const String& colorSpace)
     : m_canvas(canvas)
     , m_offscreenCanvas(offscreenCanvas)
+    , m_colorSpace(kLegacyCanvasColorSpace)
 {
+    if (RuntimeEnabledFeatures::experimentalCanvasFeaturesEnabled()) {
+        if (colorSpace == kSRGBCanvasColorSpaceName)
+            m_colorSpace = kSRGBCanvasColorSpace;
+        else if (colorSpace == kLinearRGBCanvasColorSpaceName)
+            m_colorSpace = kLinearRGBCanvasColorSpace;
+    }
+}
+
+WTF::String CanvasRenderingContext::colorSpaceAsString() const
+{
+    switch (m_colorSpace) {
+    case kSRGBCanvasColorSpace:
+        return kSRGBCanvasColorSpaceName;
+    case kLinearRGBCanvasColorSpace:
+        return kLinearRGBCanvasColorSpaceName;
+    case kLegacyCanvasColorSpace:
+        return kLegacyCanvasColorSpaceName;
+    };
+    CHECK(0);

[Stephen White, 2016/08/11 20:41:27]

Nit: CHECK(false) seems to be more common than CHECK(0).

[Justin Novosad, 2016/08/12 17:40:18]

Done.

+    return "";
+}
+
+sk_sp<SkColorSpace> CanvasRenderingContext::skColorSpace() const
+{
+    switch (m_colorSpace) {
+    case kSRGBCanvasColorSpace:
+        return SkColorSpace::NewNamed(SkColorSpace::kSRGB_Named);
+    case kLinearRGBCanvasColorSpace:
+        {
+            // Creating a temp srgb colorspace just to get the matrix.
+            // There should be a better way
+            sk_sp<SkColorSpace> tmp = SkColorSpace::NewNamed(SkColorSpace::kSRGB_Named);
+            return SkColorSpace::NewRGB(SkColorSpace::kLinear_GammaNamed, tmp->xyz());
+        }
+    case kLegacyCanvasColorSpace:
+        if (RuntimeEnabledFeatures::colorCorrectRenderingEnabled()) {
+            // Legacy colorspace ensures color matching with CSS is preserved.
+            // So if CSS is color corrected from sRGB to display space, then
+            // canvas must do the same
+            return SkColorSpace::NewNamed(SkColorSpace::kSRGB_Named);
+        }
+        return nullptr;
+    };
+    CHECK(0);

[Stephen White, 2016/08/11 20:41:27]

Ibid.

[Justin Novosad, 2016/08/12 17:40:18]

Done.

+    return nullptr;
 }
 
 void CanvasRenderingContext::dispose()
 {
     // HTMLCanvasElement and CanvasRenderingContext have a circular reference.
     // When the pair is no longer reachable, their destruction order is non-
     // deterministic, so the first of the two to be destroyed needs to notify
     // the other in order to break the circular reference.  This is to avoid
     // an error when CanvasRenderingContext2D::didProcessTask() is invoked
     // after the HTMLCanvasElement is destroyed.
@@ skipping 50 matching lines @@
     return taintOrigin;
 }
 
 DEFINE_TRACE(CanvasRenderingContext)
 {
     visitor->trace(m_canvas);
     visitor->trace(m_offscreenCanvas);
 }
 
 } // namespace blink