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LibGfx/WebP: Implement decoding of animation frame bitmaps

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With this, lossless animated webp files work :^)

(Missing: Loop count handling is not yet implemented, and alpha blending
between frames isn't done in linear space.)
This commit is contained in:
Nico Weber 2023-05-06 06:04:11 -04:00 • committed by Andreas Kling
parent 23ce1f641c
commit ce45ad6112
1 changed files with 87 additions and 3 deletions
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90
Userland/Libraries/LibGfx/ImageFormats/WebPLoader.cpp
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@ -12,6 +12,7 @@
#include <AK/Vector.h>
#include <LibCompress/Deflate.h>
#include <LibGfx/ImageFormats/WebPLoader.h>
#include <LibGfx/Painter.h>
// Overview: https://developers.google.com/speed/webp/docs/compression
// Container: https://developers.google.com/speed/webp/docs/riff_container
@ -157,6 +158,7 @@ struct WebPLoadingContext {
// These are set in state >= AnimationFrameChunksDecoded, if first_chunk.type == 'VP8X' && vp8x_header.has_animation.
Optional<ANIMChunk> animation_header_chunk_data;
Optional<Vector<ANMFChunk>> animation_frame_chunks_data;
size_t current_frame { 0 };
Optional<Chunk> iccp_chunk; // 'ICCP'
Optional<Chunk> exif_chunk; // 'EXIF'
@ -1447,7 +1449,6 @@ static ErrorOr<void> decode_webp_extended(WebPLoadingContext& context, ReadonlyB
// https://developers.google.com/speed/webp/docs/riff_container#alpha
// "A frame containing a 'VP8L' chunk SHOULD NOT contain this chunk."
// FIXME: Also check in ANMF chunks.
if (context.image_data.alpha_chunk.has_value() && context.image_data.image_data_chunk.has_value() && context.image_data.image_data_chunk->type == FourCC("VP8L")) {
dbgln_if(WEBP_DEBUG, "WebPImageDecoderPlugin: VP8L frames should not have ALPH chunks. Ignoring ALPH chunk.");
context.image_data.alpha_chunk.clear();
@ -1548,6 +1549,90 @@ static ErrorOr<void> decode_webp_animation_frame_chunks(WebPLoadingContext& cont
return {};
}
static ErrorOr<ImageData> decode_webp_animation_frame_image_data(WebPLoadingContext& context, ANMFChunk const& frame)
{
ReadonlyBytes chunks = frame.frame_data;
ImageData image_data;
auto chunk = TRY(decode_webp_advance_chunk(context, chunks));
if (chunk.type == FourCC("ALPH")) {
image_data.alpha_chunk = chunk;
chunk = TRY(decode_webp_advance_chunk(context, chunks));
}
if (chunk.type != FourCC("VP8 ") && chunk.type != FourCC("VP8L"))
return Error::from_string_literal("WebPImageDecoderPlugin: no image data found in animation frame");
image_data.image_data_chunk = chunk;
// https://developers.google.com/speed/webp/docs/riff_container#alpha
// "A frame containing a 'VP8L' chunk SHOULD NOT contain this chunk."
if (image_data.alpha_chunk.has_value() && image_data.image_data_chunk.has_value() && image_data.image_data_chunk->type == FourCC("VP8L")) {
dbgln_if(WEBP_DEBUG, "WebPImageDecoderPlugin: VP8L frames should not have ALPH chunks. Ignoring ALPH chunk.");
image_data.alpha_chunk.clear();
}
return image_data;
}
// https://developers.google.com/speed/webp/docs/riff_container#assembling_the_canvas_from_frames
static ErrorOr<ImageFrameDescriptor> decode_webp_animation_frame(WebPLoadingContext& context, size_t frame_index)
{
if (frame_index >= context.animation_frame_chunks_data->size())
return context.error("frame_index size too high");
VERIFY(context.first_chunk->type == FourCC("VP8X"));
VERIFY(context.vp8x_header.has_animation);
Color clear_color = Color::from_argb(context.animation_header_chunk_data->background_color);
size_t start_frame = context.current_frame + 1;
dbgln_if(WEBP_DEBUG, "start_frame {} context.current_frame {}", start_frame, context.current_frame);
if (context.state < WebPLoadingContext::State::BitmapDecoded) {
start_frame = 0;
context.bitmap = TRY(Bitmap::create(BitmapFormat::BGRA8888, { context.vp8x_header.width, context.vp8x_header.height }));
context.bitmap->fill(clear_color);
} else if (frame_index < context.current_frame) {
start_frame = 0;
}
Painter painter(*context.bitmap);
// FIXME: Honor context.animation_header_chunk_data.loop_count.
for (size_t i = start_frame; i <= frame_index; ++i) {
dbgln_if(WEBP_DEBUG, "drawing frame {} to produce frame {}", i, frame_index);
auto const& frame_description = context.animation_frame_chunks_data.value()[i];
if (i > 0) {
auto const& previous_frame = context.animation_frame_chunks_data.value()[i - 1];
if (previous_frame.disposal_method == ANMFChunk::DisposalMethod::DisposeToBackgroundColor)
painter.clear_rect({ previous_frame.frame_x, previous_frame.frame_y, previous_frame.frame_width, previous_frame.frame_height }, clear_color);
}
auto frame_image_data = TRY(decode_webp_animation_frame_image_data(context, frame_description));
VERIFY(frame_image_data.image_data_chunk.has_value());
if (frame_image_data.image_data_chunk->type == FourCC("VP8 "))
return context.error("WebPImageDecoderPlugin: decoding lossy webps not yet implemented");
auto frame_bitmap = TRY(decode_webp_chunk_VP8L(context, frame_image_data.image_data_chunk.value()));
if (static_cast<u32>(frame_bitmap->width()) != frame_description.frame_width || static_cast<u32>(frame_bitmap->height()) != frame_description.frame_height)
return context.error("WebPImageDecoderPlugin: decoded frame bitmap size doesn't match frame description size");
// FIXME: "Alpha-blending SHOULD be done in linear color space..."
bool apply_alpha = frame_description.blending_method == ANMFChunk::BlendingMethod::UseAlphaBlending;
painter.blit({ frame_description.frame_x, frame_description.frame_y }, *frame_bitmap, { {}, frame_bitmap->size() }, /*opacity=*/1.0, apply_alpha);
context.current_frame = i;
context.state = WebPLoadingContext::State::BitmapDecoded;
}
return ImageFrameDescriptor { context.bitmap, static_cast<int>(context.animation_frame_chunks_data.value()[frame_index].frame_duration_in_milliseconds) };
}
WebPImageDecoderPlugin::WebPImageDecoderPlugin(ReadonlyBytes data, OwnPtr<WebPLoadingContext> context)
: m_context(move(context))
{
@ -1659,8 +1744,7 @@ ErrorOr<ImageFrameDescriptor> WebPImageDecoderPlugin::frame(size_t index)
if (m_context->state < WebPLoadingContext::State::AnimationFrameChunksDecoded) {
TRY(decode_webp_animation_frame_chunks(*m_context));
}
// FIXME: Do something with the animation frames.
return Error::from_string_literal("WebPImageDecoderPlugin: decoding of animated files not yet implemented");
return decode_webp_animation_frame(*m_context, index);
}
if (m_context->image_data.image_data_chunk.has_value() && m_context->image_data.image_data_chunk->type == FourCC("VP8L")) {