Fix transfer function for TransferID::SMPTEST428_1.

The coefficients were completely wrong. I verified the correct
values suggested in the bug against ITU-T H.273.

This also resolves two comments in the test file remarking that
YCOCG and SMPTEST428_1 were "weird" due to negative values...
which was due to both matrices being wrong.

76fb0d6f fixed YCOCG, but didn't
resolve the test comments.

R=ccameron

Fixed: 1087073
Change-Id: If1d9bfe1810de81ddee1cabdf410c1f41e4602ba
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2218859
Commit-Queue: ccameron <ccameron@chromium.org>
Reviewed-by: ccameron <ccameron@chromium.org>
Auto-Submit: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#773058}

ui/gfx/color_space.cc

@@ -893,7 +893,7 @@ bool ColorSpace::GetTransferFunction(TransferID transfer,
     //    software uses the sRGB transfer function.
     //  * User studies shows that users don't really care.
     //  * Apple's CoreVideo uses gamma=1.961.
-    // Bearing all of that in mind, use the same transfer funciton as sRGB,
+    // Bearing all of that in mind, use the same transfer function as sRGB,
     // which will allow more optimization, and will more closely match other
     // media players.
     case ColorSpace::TransferID::IEC61966_2_1:
@@ -908,8 +908,7 @@ bool ColorSpace::GetTransferFunction(TransferID transfer,
       fn->g = 1.961000000000f;
       return true;
     case ColorSpace::TransferID::SMPTEST428_1:
-      fn->a = 0.225615407568f;
-      fn->e = -1.091041666667f;
+      fn->a = 1.034080527699f;  // (52.37 / 48.0) ^ (1.0 / 2.6) per ITU-T H.273.
       fn->g = 2.600000000000f;
       return true;
     case ColorSpace::TransferID::IEC61966_2_4:

ui/gfx/color_transform_unittest.cc

@@ -40,6 +40,7 @@ ColorSpace::TransferID simple_transfers[] = {
     ColorSpace::TransferID::GAMMA28,
     ColorSpace::TransferID::SMPTE170M,
     ColorSpace::TransferID::SMPTE240M,
+    ColorSpace::TransferID::SMPTEST428_1,
     ColorSpace::TransferID::LINEAR,
     ColorSpace::TransferID::LOG,
     ColorSpace::TransferID::LOG_SQRT,
@@ -53,29 +54,16 @@ ColorSpace::TransferID simple_transfers[] = {
     ColorSpace::TransferID::IEC61966_2_1_HDR,
 };
 
-// This one is weird as the non-linear numbers are not between 0 and 1.
-ColorSpace::TransferID noninvertible_transfers[] = {
-    ColorSpace::TransferID::SMPTEST428_1,
-};
-
 ColorSpace::TransferID extended_transfers[] = {
     ColorSpace::TransferID::LINEAR_HDR,
     ColorSpace::TransferID::IEC61966_2_1_HDR,
 };
 
 ColorSpace::MatrixID all_matrices[] = {
-    ColorSpace::MatrixID::RGB,
-    ColorSpace::MatrixID::BT709,
-    ColorSpace::MatrixID::FCC,
-    ColorSpace::MatrixID::BT470BG,
-    ColorSpace::MatrixID::SMPTE170M,
-    ColorSpace::MatrixID::SMPTE240M,
-
-    // YCOCG produces lots of negative values which isn't compatible with many
-    // transfer functions.
-    // TODO(hubbe): Test this separately.
-    // ColorSpace::MatrixID::YCOCG,
-    ColorSpace::MatrixID::BT2020_NCL,
+    ColorSpace::MatrixID::RGB,       ColorSpace::MatrixID::BT709,
+    ColorSpace::MatrixID::FCC,       ColorSpace::MatrixID::BT470BG,
+    ColorSpace::MatrixID::SMPTE170M, ColorSpace::MatrixID::SMPTE240M,
+    ColorSpace::MatrixID::YCOCG,     ColorSpace::MatrixID::BT2020_NCL,
     ColorSpace::MatrixID::YDZDX,
 };
 
@@ -578,35 +566,6 @@ INSTANTIATE_TEST_SUITE_P(ColorSpace,
                          TransferTest,
                          testing::ValuesIn(simple_transfers));
 
-class NonInvertibleTransferTest
-    : public testing::TestWithParam<ColorSpace::TransferID> {};
-
-TEST_P(NonInvertibleTransferTest, basicTest) {
-  gfx::ColorSpace space_with_transfer(ColorSpace::PrimaryID::BT709, GetParam(),
-                                      ColorSpace::MatrixID::RGB,
-                                      ColorSpace::RangeID::FULL);
-  gfx::ColorSpace space_linear(
-      ColorSpace::PrimaryID::BT709, ColorSpace::TransferID::LINEAR,
-      ColorSpace::MatrixID::RGB, ColorSpace::RangeID::FULL);
-
-  std::unique_ptr<ColorTransform> to_linear(ColorTransform::NewColorTransform(
-      space_with_transfer, space_linear,
-      ColorTransform::Intent::INTENT_ABSOLUTE));
-
-  std::unique_ptr<ColorTransform> from_linear(ColorTransform::NewColorTransform(
-      space_linear, space_with_transfer,
-      ColorTransform::Intent::INTENT_ABSOLUTE));
-
-  // These transforms should not crash when created or applied.
-  float x = 0.5;
-  ColorTransform::TriStim tristim(x, x, x);
-  to_linear->Transform(&tristim, 1);
-  from_linear->Transform(&tristim, 1);
-}
-
-INSTANTIATE_TEST_SUITE_P(ColorSpace,
-                         NonInvertibleTransferTest,
-                         testing::ValuesIn(noninvertible_transfers));
 
 class ExtendedTransferTest
     : public testing::TestWithParam<ColorSpace::TransferID> {};