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LibGfx/ICC+icc: Add built-in identity LAB profile using mft1 (Lut8TagData), implement conversion from PCS to it #26452

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Merged
nico merged 8 commits into from
Dec 5, 2025
+262 −29
Merged

LibGfx/ICC+icc: Add built-in identity LAB profile using mft1 (Lut8TagData), implement conversion from PCS to it #26452

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8fb76eb
LibGfx/ICC: Rename Lut{16,8}TagData::evaluate() to evaluate_to_pcs()
nico Dec 4, 2025
85dca07
LibGfx/ICC: Improve comments in Lut16TagData::evaluate_to_pcs()
nico Dec 4, 2025
01835d3
Tests/LibGfx: Rename sRGB-specific tests to have "sRGB" in their name
nico Dec 4, 2025
91f0186
Tests/LibGfx: Add a test for round-tripping through a matrix ICC profile
nico Dec 4, 2025
4478e69
LibGfx/ICC: Add a 3D->ND overload of lerp_nd()
nico Dec 4, 2025
582fb48
LibGfx/ICC: Rename rgb_header() to profile_header()
nico Dec 4, 2025
14384be
LibGfx/ICC+icc: Add a built-in identity LAB profile
nico Dec 4, 2025
5d443c8
LibGfx/ICC: Implement coverting from PCS to Lut8TagData
nico Dec 4, 2025
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26 changes: 26 additions & 0 deletions Tests/LibGfx/TestICCProfile.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -274,6 +274,32 @@ TEST_CASE(sRGB_to_lab)
EXPECT_APPROXIMATE_LAB(lab_from_sRGB(255, 255, 255), expected[7]);
}

static void test_roundtrip(Gfx::ICC::Profile const& profile)
{
// Ideally this would be 1, but that makes tests take a few minutes on fast machine.
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@LucasChollet LucasChollet Dec 4, 2025

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We could use GEN to test a different subset on every run. Which means that we should have complete coverage over time.
I'm just thinking out-loud.

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@nico nico Dec 5, 2025

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I'm a big fan of deterministic behavior 😅

// It's supposed to pass with 1, though.
int const increment = 7;
for (int a = 0; a < 256; a += increment) {
for (int b = 0; b < 256; b += increment) {
for (int c = 0; c < 256; c += increment) {
u8 color_in[3] = { static_cast<u8>(a), static_cast<u8>(b), static_cast<u8>(c) };
u8 color_out[3];
auto pcs = MUST(profile.to_pcs(color_in));
MUST(profile.from_pcs(profile, pcs, color_out));
EXPECT_EQ(color_in[0], color_out[0]);
EXPECT_EQ(color_in[1], color_out[1]);
EXPECT_EQ(color_in[2], color_out[2]);
}
}
}
}

TEST_CASE(roundtrip_sRGB_matrix_profile)
{
auto profile = TRY_OR_FAIL(Gfx::ICC::sRGB());
test_roundtrip(*profile);
}

TEST_CASE(malformed_profile)
{
Array test_inputs = {
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