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Code Issues Projects Releases Packages Wiki Activity Actions 7

LibGfx: Support APNG more completely

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This fixes 3/4 of the remaining test failures in wpt/png/apng. Also,
about half of the APNG files on
https://commons.wikimedia.org/wiki/Category:Animated_PNG_files
used to be broken, and they all seem to work properly now :^)

I also refactored the code to be (at least to me) simpler and more
similar to what the spec describes. As a nice side effect, there are now
fewer lines of code than before.

Lastly, I replaced DeprecatedPainter with Painter.
This commit is contained in:
justus2510 2024-11-04 12:03:27 +01:00 committed by Andreas Kling
parent c31d44ee18
commit 6d9dab5a29
Notes: github-actions[bot] 2024-11-05 09:38:52 +00:00 
Author: https://github.com/justus2510
Commit: https://github.com/LadybirdBrowser/ladybird/commit/6d9dab5a29f
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2155
1 changed files with 54 additions and 85 deletions
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139
Userland/Libraries/LibGfx/ImageFormats/PNGLoader.cpp
View file

@ -6,53 +6,15 @@
*/
#include <AK/Vector.h>
#include <LibGfx/DeprecatedPainter.h>
#include <LibGfx/ImageFormats/ExifOrientedBitmap.h>
#include <LibGfx/ImageFormats/PNGLoader.h>
#include <LibGfx/ImageFormats/TIFFLoader.h>
#include <LibGfx/ImageFormats/TIFFMetadata.h>
#include <LibGfx/Painter.h>
#include <png.h>
namespace Gfx {
struct AnimationFrame {
RefPtr<Bitmap> bitmap;
int x_offset { 0 };
int y_offset { 0 };
int width { 0 };
int height { 0 };
int delay_den { 0 };
int delay_num { 0 };
u8 blend_op { 0 };
u8 dispose_op { 0 };
AnimationFrame(RefPtr<Bitmap> bitmap, int x_offset, int y_offset, int width, int height, int delay_den, int delay_num, u8 blend_op, u8 dispose_op)
: bitmap(move(bitmap))
, x_offset(x_offset)
, y_offset(y_offset)
, width(width)
, height(height)
, delay_den(delay_den)
, delay_num(delay_num)
, blend_op(blend_op)
, dispose_op(dispose_op)
{
}
[[nodiscard]] int duration_ms() const
{
if (delay_num == 0)
return 1;
u32 const denominator = delay_den != 0 ? static_cast<u32>(delay_den) : 100u;
auto unsigned_duration_ms = (delay_num * 1000) / denominator;
if (unsigned_duration_ms > INT_MAX)
return INT_MAX;
return static_cast<int>(unsigned_duration_ms);
}
[[nodiscard]] IntRect rect() const { return { x_offset, y_offset, width, height }; }
};
struct PNGLoadingContext {
ReadonlyBytes data;
IntSize size;
@ -62,11 +24,6 @@ struct PNGLoadingContext {
Optional<ByteBuffer> icc_profile;
OwnPtr<ExifMetadata> exif_metadata;
Vector<AnimationFrame> animation_frames;
Vector<u8*> row_pointers;
Vector<u8> image_data;
RefPtr<Gfx::Bitmap> decoded_frame_bitmap;
ErrorOr<size_t> read_frames(png_structp, png_infop);
ErrorOr<void> apply_exif_orientation();
};
@ -226,35 +183,6 @@ ErrorOr<void> PNGLoadingContext::apply_exif_orientation()
return {};
}
static ErrorOr<NonnullRefPtr<Bitmap>> render_animation_frame(AnimationFrame const& prev_animation_frame, AnimationFrame const& animation_frame, Bitmap const& decoded_frame_bitmap)
{
auto rendered_bitmap = TRY(prev_animation_frame.bitmap->clone());
DeprecatedPainter painter(rendered_bitmap);
auto frame_rect = animation_frame.rect();
switch (prev_animation_frame.dispose_op) {
case PNG_DISPOSE_OP_BACKGROUND:
painter.clear_rect(rendered_bitmap->rect(), Color::NamedColor::Transparent);
break;
case PNG_DISPOSE_OP_PREVIOUS:
painter.blit(frame_rect.location(), decoded_frame_bitmap, frame_rect, 1.0f, false);
break;
default:
break;
}
switch (animation_frame.blend_op) {
case PNG_BLEND_OP_SOURCE:
painter.blit(frame_rect.location(), decoded_frame_bitmap, decoded_frame_bitmap.rect(), 1.0f, false);
break;
case PNG_BLEND_OP_OVER:
painter.blit(frame_rect.location(), decoded_frame_bitmap, decoded_frame_bitmap.rect(), 1.0f, true);
break;
default:
break;
}
return rendered_bitmap;
}
ErrorOr<size_t> PNGLoadingContext::read_frames(png_structp png_ptr, png_infop info_ptr)
{
if (png_get_acTL(png_ptr, info_ptr, &frame_count, &loop_count)) {
@ -262,6 +190,11 @@ ErrorOr<size_t> PNGLoadingContext::read_frames(png_structp png_ptr, png_infop in
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);
u32 width = 0;
@ -273,32 +206,67 @@ ErrorOr<size_t> PNGLoadingContext::read_frames(png_structp png_ptr, png_infop in
u8 dispose_op = PNG_DISPOSE_OP_NONE;
u8 blend_op = PNG_BLEND_OP_SOURCE;
auto duration_ms = [&]() -> int {
if (delay_num == 0)
return 1;
u32 const denominator = delay_den != 0 ? static_cast<u32>(delay_den) : 100u;
auto unsigned_duration_ms = (delay_num * 1000) / denominator;
if (unsigned_duration_ms > INT_MAX)
return INT_MAX;
return static_cast<int>(unsigned_duration_ms);
};
if (png_get_valid(png_ptr, info_ptr, PNG_INFO_fcTL)) {
png_get_next_frame_fcTL(png_ptr, info_ptr, &width, &height, &x, &y, &delay_num, &delay_den, &dispose_op, &blend_op);
} else {
width = png_get_image_width(png_ptr, info_ptr);
height = png_get_image_height(png_ptr, info_ptr);
}
auto frame_rect = FloatRect { x, y, width, height };
decoded_frame_bitmap = TRY(Bitmap::create(BitmapFormat::BGRA8888, AlphaType::Unpremultiplied, IntSize { static_cast<int>(width), static_cast<int>(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 animation_frame = AnimationFrame(nullptr, x, y, width, height, delay_den, delay_num, blend_op, dispose_op);
RefPtr<Bitmap> prev_output_buffer;
if (dispose_op == PNG_DISPOSE_OP_PREVIOUS) // Only actually clone if it's necessary
prev_output_buffer = TRY(output_buffer->clone());
if (frame_index == 0) {
animation_frame.bitmap = decoded_frame_bitmap;
frame_descriptors.append({ decoded_frame_bitmap, animation_frame.duration_ms() });
} else {
animation_frame.bitmap = TRY(render_animation_frame(animation_frames.last(), animation_frame, *decoded_frame_bitmap));
frame_descriptors.append({ animation_frame.bitmap, animation_frame.duration_ms() });
switch (blend_op) {
case PNG_BLEND_OP_SOURCE:
// All color components of the frame, including alpha, overwrite the current contents of the frame's output buffer region.
painter->clear_rect(frame_rect, Gfx::Color::Transparent);
painter->draw_bitmap(frame_rect, *decoded_frame_bitmap, decoded_frame_bitmap->rect(), Gfx::ScalingMode::NearestNeighbor, 1.0f);
break;
case PNG_BLEND_OP_OVER:
// The frame should be composited onto the output buffer based on its alpha, using a simple OVER operation as described in the "Alpha Channel Processing" section of the PNG specification.
painter->draw_bitmap(frame_rect, *decoded_frame_bitmap, decoded_frame_bitmap->rect(), ScalingMode::NearestNeighbor, 1.0f);
break;
default:
VERIFY_NOT_REACHED();
}
frame_descriptors.append({ TRY(output_buffer->clone()), duration_ms() });
switch (dispose_op) {
case PNG_DISPOSE_OP_NONE:
// No disposal is done on this frame before rendering the next; the contents of the output buffer are left as is.
break;
case PNG_DISPOSE_OP_BACKGROUND:
// The frame's region of the output buffer is to be cleared to fully transparent black before rendering the next frame.
painter->clear_rect(frame_rect, Gfx::Color::Transparent);
break;
case PNG_DISPOSE_OP_PREVIOUS:
// The frame's region of the output buffer is to be reverted to the previous contents before rendering the next frame.
painter->clear_rect(frame_rect, Gfx::Color::Transparent);
painter->draw_bitmap(frame_rect, *prev_output_buffer, IntRect { x, y, width, height }, Gfx::ScalingMode::NearestNeighbor, 1.0f);
break;
default:
VERIFY_NOT_REACHED();
}
animation_frames.append(move(animation_frame));
}
} else {
// This is a single-frame PNG.
@ -306,7 +274,8 @@ ErrorOr<size_t> PNGLoadingContext::read_frames(png_structp png_ptr, png_infop in
frame_count = 1;
loop_count = 0;
decoded_frame_bitmap = TRY(Bitmap::create(BitmapFormat::BGRA8888, AlphaType::Unpremultiplied, size));
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);