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ICC: Implement some of Profile::from_pcs()

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This implements conversion from profile connection space to the
device-dependent color for matrix-based profiles.

It only does the inverse color transform but does not yet do the
inverse tone reproduction curve transform -- i.e. it doesn't
implement many cases (LUT transforms), and it does the one thing
it does implement incorrectly. But to vindicate the commit a bit,
it also does the incorrect thing very inefficiently.
This commit is contained in:
Nico Weber 2023-05-01 08:24:13 -04:00 • committed by Sam Atkins
parent 2319b2ffb5
commit 4169c94ebe
3 changed files with 167 additions and 0 deletions
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34
Tests/LibGfx/TestICCProfile.cpp
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@ -154,6 +154,40 @@ TEST_CASE(to_pcs)
EXPECT_APPROXIMATE_VECTOR3(xyz_from_sRGB(64, 128, 192), r_xyz * f64 + g_xyz * f128 + b_xyz * f192);
}
TEST_CASE(from_pcs)
{
auto sRGB = MUST(Gfx::ICC::sRGB());
auto sRGB_from_xyz = [&sRGB](FloatVector3 const& XYZ) {
u8 rgb[3];
MUST(sRGB->from_pcs(XYZ, rgb));
return Color(rgb[0], rgb[1], rgb[2]);
};
auto vec3_from_xyz = [](Gfx::ICC::XYZ const& xyz) {
return FloatVector3 { xyz.X, xyz.Y, xyz.Z };
};
// At 0 and 255, the gamma curve is (exactly) 0 and 1, so these just test the matrix part.
EXPECT_EQ(sRGB_from_xyz(FloatVector3 { 0, 0, 0 }), Color(0, 0, 0));
auto r_xyz = vec3_from_xyz(sRGB->red_matrix_column());
EXPECT_EQ(sRGB_from_xyz(r_xyz), Color(255, 0, 0));
auto g_xyz = vec3_from_xyz(sRGB->green_matrix_column());
EXPECT_EQ(sRGB_from_xyz(g_xyz), Color(0, 255, 0));
auto b_xyz = vec3_from_xyz(sRGB->blue_matrix_column());
EXPECT_EQ(sRGB_from_xyz(b_xyz), Color(0, 0, 255));
EXPECT_EQ(sRGB_from_xyz(r_xyz + g_xyz), Color(255, 255, 0));
EXPECT_EQ(sRGB_from_xyz(r_xyz + b_xyz), Color(255, 0, 255));
EXPECT_EQ(sRGB_from_xyz(g_xyz + b_xyz), Color(0, 255, 255));
EXPECT_EQ(sRGB_from_xyz(r_xyz + g_xyz + b_xyz), Color(255, 255, 255));
// FIXME: Implement and test the inverse curve transform.
}
TEST_CASE(to_lab)
{
auto sRGB = MUST(Gfx::ICC::sRGB());