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LibGfx: Factor out PNG frame decoding logic

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The logic for decoding APNGs and single-frame PNGs had some duplicated
code. No functional changes.
This commit is contained in:
Jelle Raaijmakers 2025-02-26 16:38:13 +01:00
parent 9e3391b850
commit 2102546d32
1 changed files with 14 additions and 16 deletions
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30
Libraries/LibGfx/ImageFormats/PNGLoader.cpp
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@ -248,15 +248,25 @@ ErrorOr<void> PNGLoadingContext::apply_exif_orientation()
ErrorOr<size_t> PNGLoadingContext::read_frames(png_structp png_ptr, png_infop info_ptr)
{
Vector<u8*> row_pointers;
auto decode_frame = [&](IntSize frame_size) -> ErrorOr<NonnullRefPtr<Bitmap>> {
auto frame_bitmap = TRY(Bitmap::create(BitmapFormat::BGRA8888, AlphaType::Unpremultiplied, frame_size));
row_pointers.resize_and_keep_capacity(frame_size.height());
for (auto i = 0; i < frame_size.height(); ++i)
row_pointers[i] = frame_bitmap->scanline_u8(i);
png_read_image(png_ptr, row_pointers.data());
return frame_bitmap;
};
if (png_get_acTL(png_ptr, info_ptr, &frame_count, &loop_count)) {
// acTL chunk present: This is an APNG.
png_set_acTL(png_ptr, info_ptr, frame_count, loop_count);
// Conceptually, at the beginning of each play the output buffer must be completely initialized to a fully transparent black rectangle, with width and height dimensions from the `IHDR` chunk.
auto output_buffer = TRY(Bitmap::create(BitmapFormat::BGRA8888, AlphaType::Unpremultiplied, size));
auto painter = Painter::create(output_buffer);
Vector<u8*> row_pointers;
for (size_t frame_index = 0; frame_index < frame_count; ++frame_index) {
png_read_frame_head(png_ptr, info_ptr);
@ -287,12 +297,7 @@ ErrorOr<size_t> PNGLoadingContext::read_frames(png_structp png_ptr, png_infop in
}
auto frame_rect = FloatRect { x, y, width, height };
auto decoded_frame_bitmap = TRY(Bitmap::create(BitmapFormat::BGRA8888, AlphaType::Unpremultiplied, IntSize { static_cast<int>(width), static_cast<int>(height) }));
row_pointers.resize(height);
for (u32 i = 0; i < height; ++i) {
row_pointers[i] = decoded_frame_bitmap->scanline_u8(i);
}
png_read_image(png_ptr, row_pointers.data());
auto decoded_frame_bitmap = TRY(decode_frame({ width, height }));
RefPtr<Bitmap> prev_output_buffer;
if (dispose_op == PNG_DISPOSE_OP_PREVIOUS) // Only actually clone if it's necessary
@ -331,17 +336,10 @@ ErrorOr<size_t> PNGLoadingContext::read_frames(png_structp png_ptr, png_infop in
}
} else {
// This is a single-frame PNG.
frame_count = 1;
loop_count = 0;
auto decoded_frame_bitmap = TRY(Bitmap::create(BitmapFormat::BGRA8888, AlphaType::Unpremultiplied, size));
Vector<u8*> row_pointers;
row_pointers.resize(size.height());
for (int i = 0; i < size.height(); ++i)
row_pointers[i] = decoded_frame_bitmap->scanline_u8(i);
png_read_image(png_ptr, row_pointers.data());
auto decoded_frame_bitmap = TRY(decode_frame(size));
frame_descriptors.append({ move(decoded_frame_bitmap), 0 });
}
return this->frame_count;