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LibGfx/AnimationWriter: Survive animations with two identical frames

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Creating a completely empty bitmap fails. Just write a 1x1 bitmap
if the bitmap ends up empty for now.
This commit is contained in:
Nico Weber 2024-05-21 16:20:38 -04:00 • committed by Tim Flynn
commit b7b51d01c3
Notes: sideshowbarker 2024-07-17 03:51:15 +09:00
2 changed files with 38 additions and 0 deletions
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31
Tests/LibGfx/TestImageWriter.cpp
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@ -229,3 +229,34 @@ TEST_CASE(test_webp_incremental_animation)
EXPECT_EQ(frame1.duration, 200);
expect_bitmaps_equal(*frame1.image, *rgb_bitmap_2);
}
TEST_CASE(test_webp_incremental_animation_two_identical_frames)
{
auto rgb_bitmap = TRY_OR_FAIL(create_test_rgba_bitmap());
rgb_bitmap = TRY_OR_FAIL(rgb_bitmap->cropped({ 0, 0, 40, 20 })); // Even-sized.
// 20 kiB is enough for two 47x33 frames.
auto stream_buffer = TRY_OR_FAIL(ByteBuffer::create_uninitialized(20 * 1024));
FixedMemoryStream stream { Bytes { stream_buffer } };
auto animation_writer = TRY_OR_FAIL(Gfx::WebPWriter::start_encoding_animation(stream, rgb_bitmap->size()));
TRY_OR_FAIL(animation_writer->add_frame(*rgb_bitmap, 100));
TRY_OR_FAIL(animation_writer->add_frame_relative_to_last_frame(*rgb_bitmap, 200, *rgb_bitmap));
auto encoded_animation = ReadonlyBytes { stream_buffer.data(), stream.offset() };
auto decoded_animation_plugin = TRY_OR_FAIL(Gfx::WebPImageDecoderPlugin::create(encoded_animation));
EXPECT(decoded_animation_plugin->is_animated());
EXPECT_EQ(decoded_animation_plugin->frame_count(), 2u);
EXPECT_EQ(decoded_animation_plugin->loop_count(), 0u);
EXPECT_EQ(decoded_animation_plugin->size(), rgb_bitmap->size());
auto frame0 = TRY_OR_FAIL(decoded_animation_plugin->frame(0));
EXPECT_EQ(frame0.duration, 100);
expect_bitmaps_equal(*frame0.image, *rgb_bitmap);
auto frame1 = TRY_OR_FAIL(decoded_animation_plugin->frame(1));
EXPECT_EQ(frame1.duration, 200);
expect_bitmaps_equal(*frame1.image, *rgb_bitmap);
}

7
Userland/Libraries/LibGfx/ImageFormats/AnimationWriter.cpp
View file

@ -80,6 +80,13 @@ ErrorOr<void> AnimationWriter::add_frame_relative_to_last_frame(Bitmap& frame, i
auto rect = rect_where_pixels_are_different(*last_frame, frame);
if (rect.is_empty()) {
// The frame is identical to the last frame. Don't store an empty bitmap.
// FIXME: We could delay writing the last frame until we know that the next frame is different,
// and just keep increasing that frame's duration instead.
rect = { 0, 0, 1, 1 };
}
// FIXME: It would be nice to have a way to crop a bitmap without copying the data.
auto differences = TRY(frame.cropped(rect));