color: Don't use QCMS for transforms unless necessary

ui/gfx/color_transform.cc

 // Copyright (c) 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/gfx/color_transform.h"
 
 #include <algorithm>
 #include <cmath>
 #include <list>
 #include <memory>
@@ skipping 259 matching lines @@
       step->Transform(colors, num);
   }
   size_t NumberOfStepsForTesting() const override { return steps_.size(); }
 
  private:
   void AppendColorSpaceToColorSpaceTransform(ColorSpace from,
                                              const ColorSpace& to,
                                              ColorTransform::Intent intent);
   void Simplify();
 
+  // Retrieve the ICC profile from which |color_space| was created, only if that
+  // is a more precise representation of the color space than the primaries and
+  // transfer function in |color_space|.
+  ScopedQcmsProfile GetQCMSProfileIfNecessary(const ColorSpace& color_space);
+
   std::list<std::unique_ptr<ColorTransformStep>> steps_;
 };
 
 class ColorTransformNull : public ColorTransformStep {
  public:
   ColorTransformNull* GetNull() override { return this; }
   bool IsNull() override { return true; }
   void Transform(ColorTransform::TriStim* color, size_t num) override {}
 };
 
@@ skipping 243 matching lines @@
   }
 
  private:
   bool null_ = false;
 };
 
 void ColorTransformInternal::AppendColorSpaceToColorSpaceTransform(
     ColorSpace from,
     const ColorSpace& to,
     ColorTransform::Intent intent) {
+  // If the source was not specified, assume that it was sRGB.
+  if (!from.IsValid())

[hubbe, 2017/02/16 08:33:02]

Can we just remove this?

[ccameron, 2017/02/16 22:33:10]

Oops, yes, that was dead code.

+    from = gfx::ColorSpace::CreateSRGB();
+
   if (intent == ColorTransform::Intent::INTENT_PERCEPTUAL) {
     switch (from.transfer_) {
       case ColorSpace::TransferID::BT709:
       case ColorSpace::TransferID::SMPTE170M:
         // SMPTE 1886 suggests that we should be using gamma 2.4 for BT709
         // content. However, most displays actually use a gamma of 2.2, and
         // user studies shows that users don't really care. Using the same
         // gamma as the display will let us optimize a lot more, so lets stick
         // with using the SRGB transfer function.
         from.transfer_ = ColorSpace::TransferID::IEC61966_2_1;
@@ skipping 93 matching lines @@
     qcms_chain_transform(from_.get(), to_.get(),
                          reinterpret_cast<float*>(colors),
                          reinterpret_cast<float*>(colors), num * 3);
   }
 
  private:
   ScopedQcmsProfile from_;
   ScopedQcmsProfile to_;
 };
 
-ScopedQcmsProfile GetQCMSProfileIfAvailable(const ColorSpace& color_space) {
-  ICCProfile icc_profile = ICCProfile::FromColorSpace(color_space);
-  if (icc_profile.GetData().empty())
+ScopedQcmsProfile ColorTransformInternal::GetQCMSProfileIfNecessary(
+    const ColorSpace& color_space) {
+  ICCProfile icc_profile;
+  if (!ICCProfile::FromId(color_space.icc_profile_id_, true, &icc_profile))
     return nullptr;
   return ScopedQcmsProfile(qcms_profile_from_memory(
       icc_profile.GetData().data(), icc_profile.GetData().size()));
 }
 
 ScopedQcmsProfile GetXYZD50Profile() {
   // QCMS is trixy, it has a datatype called qcms_CIE_xyY, but what it expects
   // is in fact not xyY color coordinates, it just wants the x/y values of the
   // primaries with Y equal to 1.0.
   qcms_CIE_xyYTRIPLE xyz;
@@ skipping 14 matching lines @@
 }
 
 ColorTransformInternal::ColorTransformInternal(const ColorSpace& from,
                                                const ColorSpace& to,
                                                Intent intent) {
   // If no source color space is specified, do no transformation.
   // TODO(ccameron): We may want to assume sRGB at some point in the future.
   if (!from.IsValid())
     return;
 
-  ScopedQcmsProfile from_profile = GetQCMSProfileIfAvailable(from);
-  ScopedQcmsProfile to_profile = GetQCMSProfileIfAvailable(to);
+  ScopedQcmsProfile from_profile = GetQCMSProfileIfNecessary(from);
+  ScopedQcmsProfile to_profile = GetQCMSProfileIfNecessary(to);
   bool has_from_profile = !!from_profile;
   bool has_to_profile = !!to_profile;
 
   if (from_profile) {
     steps_.push_back(base::MakeUnique<QCMSColorTransform>(
         std::move(from_profile), GetXYZD50Profile()));
   }
 
   AppendColorSpaceToColorSpaceTransform(
       has_from_profile ? ColorSpace::CreateXYZD50() : from,
@@ skipping 47 matching lines @@
     const ColorSpace& to,
     Intent intent) {
   return std::unique_ptr<ColorTransform>(
       new ColorTransformInternal(from, to, intent));
 }
 
 ColorTransform::ColorTransform() {}
 ColorTransform::~ColorTransform() {}
 
 }  // namespace gfx