color: general transformation -> affine transformation

ui/gfx/color_transform_unittest.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 "base/logging.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/gfx/color_space.h"
 #include "ui/gfx/color_transform.h"
 #include "ui/gfx/icc_profile.h"
 #include "ui/gfx/transform.h"
@@ skipping 65 matching lines @@
   EXPECT_NEAR(tmp.y(), 1.0f, 0.001f);
   EXPECT_NEAR(tmp.z(), 1.0f, 0.001f);
 
   // Test a blue color
   tmp = ColorTransform::TriStim(128.0f / 255.0f, 240.0f / 255.0f, 0.5f);
   t->transform(&tmp, 1);
   EXPECT_GT(tmp.z(), tmp.x());
   EXPECT_GT(tmp.z(), tmp.y());
 }
 
+TEST(SimpleColorSpace, GetAffineApproximation) {
+  // Two linear color spaces, result should be a perfect translation.
+  ColorSpace from_colorspace(
+      ColorSpace::PrimaryID::BT709, ColorSpace::TransferID::LINEAR,
+      ColorSpace::MatrixID::BT709, ColorSpace::RangeID::FULL);
+  ColorSpace to_colorspace(
+      ColorSpace::PrimaryID::BT2020, ColorSpace::TransferID::LINEAR,
+      ColorSpace::MatrixID::RGB, ColorSpace::RangeID::FULL);
+
+  std::unique_ptr<ColorTransform> t(ColorTransform::NewColorTransform(
+      from_colorspace, to_colorspace, ColorTransform::Intent::INTENT_ABSOLUTE));
+  Transform transform;
+  EXPECT_TRUE(t->GetAffineApproximation(&transform));
+
+  for (int x = 0; x <= 2; x++) {
+    for (int y = 0; y <= 2; y++) {
+      for (int z = 0; z <= 2; z++) {
+        ColorTransform::TriStim A(x / 2.0f, y / 2.0f, z / 2.0f);
+        ColorTransform::TriStim B(A);
+        t->transform(&A, 1);
+        transform.TransformPoint(&B);
+        EXPECT_NEAR(A.x(), B.x(), 0.001);
+        EXPECT_NEAR(A.y(), B.y(), 0.001);
+        EXPECT_NEAR(A.z(), B.z(), 0.001);
+      }
+    }
+  }
+}
+
 unsigned char srgb_icc_data[] = {
     0x00, 0x00, 0x0b, 0xe8, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00,
     0x6d, 0x6e, 0x74, 0x72, 0x52, 0x47, 0x42, 0x20, 0x58, 0x59, 0x5a, 0x20,
     0x07, 0xd9, 0x00, 0x03, 0x00, 0x1b, 0x00, 0x15, 0x00, 0x24, 0x00, 0x1f,
     0x61, 0x63, 0x73, 0x70, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xf6, 0xd6,
     0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0xd3, 0x2d, 0x00, 0x00, 0x00, 0x00,
     0x12, 0xe2, 0xc7, 0xe9, 0xc6, 0x02, 0x6e, 0x10, 0x5e, 0xdb, 0x15, 0x15,
     0x9c, 0x6f, 0x26, 0xed, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
@@ skipping 431 matching lines @@
                      testing::ValuesIn(all_ranges)));
 
 INSTANTIATE_TEST_CASE_P(
     C,
     ColorSpaceTest,
     testing::Combine(testing::ValuesIn(all_primaries),
                      testing::Values(ColorSpace::TransferID::BT709),
                      testing::ValuesIn(all_matrices),
                      testing::ValuesIn(all_ranges)));
 }  // namespace