From da48238fbdf4158e45a45f0d8214563e37b24cd3 Mon Sep 17 00:00:00 2001
From: Nico Weber <thakis@chromium.org>
Date: Mon, 19 Jun 2023 21:07:17 -0400
Subject: [PATCH] Tests: Add test for webp with color index transform and
 alpha_used=false

This just works at the moment after e19892a099a1, but if we ever do
the FIXME in ColorIndexingTransform::transform(), this test will
remind us to think of this case there too.

catdog-alert-13-alpha-used-false.webp is identical to
catdog-alert-13.web but with the byte at offset 0x2a changed from
0x10 to 0x00  -- that is, the bit in the VP8L header that stores
`is_alpha_used` is cleared.

See the commit message of e19892a099a1 for more information.
---
 Tests/LibGfx/TestImageDecoder.cpp                 |   3 +++
 .../webp/catdog-alert-13-alpha-used-false.webp    | Bin 0 -> 400 bytes
 2 files changed, 3 insertions(+)
 create mode 100644 Tests/LibGfx/test-inputs/webp/catdog-alert-13-alpha-used-false.webp

diff --git a/Tests/LibGfx/TestImageDecoder.cpp b/Tests/LibGfx/TestImageDecoder.cpp
index 9717a1c48e..385846be49 100644
--- a/Tests/LibGfx/TestImageDecoder.cpp
+++ b/Tests/LibGfx/TestImageDecoder.cpp
@@ -492,11 +492,14 @@ TEST_CASE(test_webp_simple_lossless_color_index_transform_pixel_bundling)
     // catdog-alert-2 tests the 1-bit-per-pixel case,
     // catdog-alert-3 tests the 2-bit-per-pixel case,
     // catdog-alert-8 and catdog-alert-13 both test the 4-bits-per-pixel case.
+    // catdog-alert-13-alpha-used-false is like catdog-alert-13, but with is_alpha_used set to false in the header
+    // (which has the effect of ignoring the alpha information in the palette and instead always setting alpha to 0xff).
     TestCase test_cases[] = {
         { "webp/catdog-alert-2.webp"sv, Gfx::Color(0x35, 0x12, 0x0a, 0xff), Gfx::Color(0xf3, 0xe6, 0xd8, 0xff) },
         { "webp/catdog-alert-3.webp"sv, Gfx::Color(0x35, 0x12, 0x0a, 0xff), Gfx::Color(0, 0, 0, 0) },
         { "webp/catdog-alert-8.webp"sv, Gfx::Color(0, 0, 0, 255), Gfx::Color(0, 0, 0, 0) },
         { "webp/catdog-alert-13.webp"sv, Gfx::Color(0, 0, 0, 255), Gfx::Color(0, 0, 0, 0) },
+        { "webp/catdog-alert-13-alpha-used-false.webp"sv, Gfx::Color(0, 0, 0, 255), Gfx::Color(0, 0, 0, 255) },
     };
 
     for (auto test_case : test_cases) {
diff --git a/Tests/LibGfx/test-inputs/webp/catdog-alert-13-alpha-used-false.webp b/Tests/LibGfx/test-inputs/webp/catdog-alert-13-alpha-used-false.webp
new file mode 100644
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