Add support for transfer functions to GrColorSpaceXform

With this change, untagged sources (eg N32) are treated as
sRGB data, which causes a huge number of GMs to render more
correctly in GPU sRGB/F16/etc... configs. Also, because the
sources are treated as having a color space, we actually do
gamut conversion for wide or narrow gamut outputs.

This change also applies the transfer function math to
individual colors in the case of gradient stops and color
shaders. (The CPU backend doesn't do this yet, but I think
we've decided there's no reason not to support it).

Bug: skia:
Change-Id: If76e9e4a268f9f74110ff4bbe4fe189ba5d19d9f
Reviewed-on: https://skia-review.googlesource.com/64100
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/src/shaders/SkColorShader.cpp b/src/shaders/SkColorShader.cpp
index 4bc7d71194..861898737b 100644
--- a/src/shaders/SkColorShader.cpp
+++ b/src/shaders/SkColorShader.cpp
@@ -211,8 +211,10 @@ SkShader::GradientType SkColor4Shader::asAGradient(GradientInfo* info) const {
 
 std::unique_ptr<GrFragmentProcessor> SkColor4Shader::asFragmentProcessor(
         const AsFPArgs& args) const {
-    sk_sp<GrColorSpaceXform> colorSpaceXform =
-            GrColorSpaceXform::Make(fColorSpace.get(), args.fDstColorSpaceInfo->colorSpace());
+    // Construct an xform assuming float inputs. The color space can have a transfer function on
+    // it, which will be applied below.
+    auto colorSpaceXform = GrColorSpaceXform::Make(fColorSpace.get(), kRGBA_float_GrPixelConfig,
+                                                   args.fDstColorSpaceInfo->colorSpace());
     GrColor4f color = GrColor4f::FromSkColor4f(fColor4);
     if (colorSpaceXform) {
         color = colorSpaceXform->clampedXform(color);