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LibWeb+LibGfx: Move the blit image through 2D transfrom to Gfx::Painter

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Even though this code is obnoxiously slow, it still belongs in LibGfx
and should not be hidden away in LibWeb's CanvasRenderingContext2D.
This commit is contained in:
Andreas Kling 2022-09-24 13:00:53 +02:00
parent 37ea6de772
commit b52165c5d7
3 changed files with 59 additions and 54 deletions
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57
Userland/Libraries/LibGfx/Painter.cpp
View file

@ -31,6 +31,7 @@
#include <LibGfx/FillPathImplementation.h>
#include <LibGfx/Palette.h>
#include <LibGfx/Path.h>
#include <LibGfx/Quad.h>
#include <LibGfx/TextDirection.h>
#include <LibGfx/TextLayout.h>
#include <stdio.h>
@ -2423,4 +2424,60 @@ void Painter::draw_text_run(FloatPoint const& baseline_start, Utf8View const& st
}
}
void Painter::draw_scaled_bitmap_with_transform(Gfx::IntRect const& dst_rect, Gfx::Bitmap const& bitmap, Gfx::FloatRect const& src_rect, Gfx::AffineTransform const& transform, float opacity, Gfx::Painter::ScalingMode scaling_mode)
{
if (transform.is_identity_or_translation()) {
translate(transform.e(), transform.f());
draw_scaled_bitmap(dst_rect, bitmap, src_rect, opacity, scaling_mode);
translate(-transform.e(), -transform.f());
} else {
// The painter has an affine transform, we have to draw through it!
// FIXME: This is *super* inefficient.
// What we currently do, roughly:
// - Map the destination rect through the context's transform.
// - Compute the bounding rect of the destination quad.
// - For each point in the computed bounding rect, reverse-map it to a point in the source image.
// - Sample the source image at the computed point.
// - Set or blend (depending on alpha values) one pixel in the canvas.
// - Loop.
// FIXME: Painter should have an affine transform as part of its state and handle all of this instead.
auto inverse_transform = transform.inverse();
if (!inverse_transform.has_value())
return;
auto destination_quad = transform.map_to_quad(dst_rect.to_type<float>());
auto destination_bounding_rect = destination_quad.bounding_rect().to_rounded<int>();
Gfx::AffineTransform source_transform;
source_transform.translate(src_rect.x(), src_rect.y());
source_transform.scale(src_rect.width() / dst_rect.width(), src_rect.height() / dst_rect.height());
source_transform.translate(-dst_rect.x(), -dst_rect.y());
for (int y = destination_bounding_rect.y(); y <= destination_bounding_rect.bottom(); ++y) {
for (int x = destination_bounding_rect.x(); x <= destination_bounding_rect.right(); ++x) {
auto destination_point = Gfx::IntPoint { x, y };
if (!clip_rect().contains(destination_point))
continue;
if (!destination_quad.contains(destination_point.to_type<float>()))
continue;
auto source_point = source_transform.map(inverse_transform->map(destination_point)).to_rounded<int>();
if (!bitmap.rect().contains(source_point))
continue;
auto source_color = bitmap.get_pixel(source_point);
if (source_color.alpha() == 0)
continue;
if (source_color.alpha() == 255) {
set_pixel(destination_point, source_color);
continue;
}
auto dst_color = target()->get_pixel(destination_point);
set_pixel(destination_point, dst_color.blend(source_color));
}
}
}
}
}