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LibWeb: Factor out canvas serialization algorihtm

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Factor out canvas serialization algorihtm from HTMLCanvasElement to
seperate file. This makes it usable by other things too.
This commit is contained in:
Totto16 2025-03-06 23:37:13 +01:00 • committed by Andrew Kaster
parent 8ef7df2a95
commit 49500ac386
Notes: github-actions[bot] 2025-06-30 15:47:56 +00:00
4 changed files with 68 additions and 34 deletions
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42
Libraries/LibWeb/HTML/HTMLCanvasElement.cpp
View file

@ -6,10 +6,7 @@
#include <AK/Base64.h>
#include <AK/Checked.h>
#include <AK/MemoryStream.h>
#include <LibGfx/Bitmap.h>
#include <LibGfx/ImageFormats/JPEGWriter.h>
#include <LibGfx/ImageFormats/PNGWriter.h>
#include <LibWeb/Bindings/ExceptionOrUtils.h>
#include <LibWeb/Bindings/HTMLCanvasElementPrototype.h>
#include <LibWeb/CSS/ComputedProperties.h>
@ -19,6 +16,7 @@
#include <LibWeb/CSS/StyleValues/RatioStyleValue.h>
#include <LibWeb/CSS/StyleValues/StyleValueList.h>
#include <LibWeb/DOM/Document.h>
#include <LibWeb/HTML/Canvas/SerializeBitmap.h>
#include <LibWeb/HTML/CanvasRenderingContext2D.h>
#include <LibWeb/HTML/HTMLCanvasElement.h>
#include <LibWeb/HTML/Numbers.h>
@ -289,35 +287,8 @@ Gfx::IntSize HTMLCanvasElement::bitmap_size_for_canvas(size_t minimum_width, siz
return Gfx::IntSize(width, height);
}
struct SerializeBitmapResult {
ByteBuffer buffer;
StringView mime_type;
};
// https://html.spec.whatwg.org/multipage/canvas.html#a-serialisation-of-the-bitmap-as-a-file
static ErrorOr<SerializeBitmapResult> serialize_bitmap(Gfx::Bitmap const& bitmap, StringView type, JS::Value quality)
{
// If type is an image format that supports variable quality (such as "image/jpeg"), quality is given, and type is not "image/png", then,
// if quality is a Number in the range 0.0 to 1.0 inclusive, the user agent must treat quality as the desired quality level.
// Otherwise, the user agent must use its default quality value, as if the quality argument had not been given.
bool valid_quality = quality.is_number() && quality.as_double() >= 0.0 && quality.as_double() <= 1.0;
if (type.equals_ignoring_ascii_case("image/jpeg"sv)) {
AllocatingMemoryStream file;
Gfx::JPEGWriter::Options jpeg_options;
if (valid_quality)
jpeg_options.quality = static_cast<int>(quality.as_double() * 100);
TRY(Gfx::JPEGWriter::encode(file, bitmap, jpeg_options));
return SerializeBitmapResult { TRY(file.read_until_eof()), "image/jpeg"sv };
}
// User agents must support PNG ("image/png"). User agents may support other types.
// If the user agent does not support the requested type, then it must create the file using the PNG format. [PNG]
return SerializeBitmapResult { TRY(Gfx::PNGWriter::encode(bitmap)), "image/png"sv };
}
// https://html.spec.whatwg.org/multipage/canvas.html#dom-canvas-todataurl
String HTMLCanvasElement::to_data_url(StringView type, JS::Value quality)
String HTMLCanvasElement::to_data_url(StringView type, JS::Value js_quality)
{
// It is possible the canvas doesn't have a associated bitmap so create one
allocate_painting_surface_if_needed();
@ -340,7 +311,8 @@ String HTMLCanvasElement::to_data_url(StringView type, JS::Value quality)
auto snapshot = Gfx::ImmutableBitmap::create_snapshot_from_painting_surface(*surface);
auto bitmap = MUST(Gfx::Bitmap::create(Gfx::BitmapFormat::BGRA8888, Gfx::AlphaType::Premultiplied, surface->size()));
surface->read_into_bitmap(*bitmap);
auto file = serialize_bitmap(bitmap, type, move(quality));
Optional<double> quality = js_quality.is_number() ? js_quality.as_double() : Optional<double>();
auto file = serialize_bitmap(bitmap, type, quality);
// 4. If file is null, then return "data:,".
if (file.is_error()) {
@ -357,7 +329,7 @@ String HTMLCanvasElement::to_data_url(StringView type, JS::Value quality)
}
// https://html.spec.whatwg.org/multipage/canvas.html#dom-canvas-toblob
WebIDL::ExceptionOr<void> HTMLCanvasElement::to_blob(GC::Ref<WebIDL::CallbackType> callback, StringView type, JS::Value quality)
WebIDL::ExceptionOr<void> HTMLCanvasElement::to_blob(GC::Ref<WebIDL::CallbackType> callback, StringView type, JS::Value js_quality)
{
// It is possible the canvas doesn't have a associated bitmap so create one
allocate_painting_surface_if_needed();
@ -381,12 +353,14 @@ WebIDL::ExceptionOr<void> HTMLCanvasElement::to_blob(GC::Ref<WebIDL::CallbackTyp
surface->read_into_bitmap(*bitmap_result);
}
Optional<double> quality = js_quality.is_number() ? js_quality.as_double() : Optional<double>();
// 4. Run these steps in parallel:
Platform::EventLoopPlugin::the().deferred_invoke(GC::create_function(heap(), [this, callback, bitmap_result, type, quality] {
// 1. If result is non-null, then set result to a serialization of result as a file with type and quality if given.
Optional<SerializeBitmapResult> file_result;
if (bitmap_result) {
if (auto result = serialize_bitmap(*bitmap_result, type, move(quality)); !result.is_error())
if (auto result = serialize_bitmap(*bitmap_result, type, quality); !result.is_error())
file_result = result.release_value();
}