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LibWeb: Support CRC2D.drawImage() with affine transform
Previously, we only remapped the destination rect through the context's affine transform, but didn't actually paint through it. This patch fixes that by implementing a very inefficient algorithm for rasterizing a transformed bitmap. When the context has a plain identity transform, we bypass this algorithm in favor of calling Gfx::Painter directly as we did before. This makes the player character in "Biolab Disaster" able to turn left!
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1 changed files with 53 additions and 2 deletions
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@ -9,6 +9,7 @@
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#include <AK/ExtraMathConstants.h>
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#include <AK/OwnPtr.h>
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#include <LibGfx/Painter.h>
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#include <LibGfx/Quad.h>
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#include <LibGfx/Rect.h>
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#include <LibWeb/Bindings/CanvasRenderingContext2DWrapper.h>
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#include <LibWeb/Bindings/WindowObject.h>
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@ -179,8 +180,58 @@ DOM::ExceptionOr<void> CanvasRenderingContext2D::draw_image(CanvasImageSource co
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auto painter = this->painter();
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if (!painter)
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return {};
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auto transformed_destination_rect = m_drawing_state.transform.map(destination_rect);
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painter->draw_scaled_bitmap(transformed_destination_rect.to_rounded<int>(), *bitmap, source_rect, 1.0f, Gfx::Painter::ScalingMode::BilinearBlend);
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if (m_drawing_state.transform.is_identity()) {
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// There's no affine transformation to worry about, we can just call Gfx::Painter.
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painter->draw_scaled_bitmap(destination_rect.to_rounded<int>(), *bitmap, source_rect, 1.0f, Gfx::Painter::ScalingMode::BilinearBlend);
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} else {
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// The context has an affine transform, we have to draw through it!
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// FIXME: This is *super* inefficient.
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// What we currently do, roughly:
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// - Map the destination rect through the context's transform.
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// - Compute the bounding rect of the destination quad.
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// - For each point in the computed bounding rect, reverse-map it to a point in the source image.
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// - Sample the source image at the computed point.
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// - Set or blend (depending on alpha values) one pixel in the canvas.
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// - Loop.
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// FIXME: Gfx::Painter should have an affine transform as part of its state and handle all of this instead.
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auto inverse_transform = m_drawing_state.transform.inverse();
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if (!inverse_transform.has_value())
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return {};
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auto destination_quad = m_drawing_state.transform.map_to_quad(destination_rect);
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auto destination_bounding_rect = destination_quad.bounding_rect().to_rounded<int>();
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Gfx::AffineTransform source_transform;
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source_transform.translate(source_x, source_y);
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source_transform.scale(source_width / destination_width, source_height / destination_height);
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source_transform.translate(-destination_x, -destination_y);
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for (int y = destination_bounding_rect.y(); y <= destination_bounding_rect.bottom(); ++y) {
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for (int x = destination_bounding_rect.x(); x <= destination_bounding_rect.right(); ++x) {
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auto destination_point = Gfx::IntPoint { x, y };
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if (!painter->clip_rect().contains(destination_point))
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continue;
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if (!destination_quad.contains(destination_point.to_type<float>()))
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continue;
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auto source_point = source_transform.map(inverse_transform->map(destination_point)).to_rounded<int>();
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if (!bitmap->rect().contains(source_point))
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continue;
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auto source_color = bitmap->get_pixel(source_point);
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if (source_color.alpha() == 0)
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continue;
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if (source_color.alpha() == 255) {
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painter->set_pixel(destination_point, source_color);
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continue;
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}
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auto dst_color = painter->target()->get_pixel(destination_point);
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painter->set_pixel(destination_point, dst_color.blend(source_color));
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}
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}
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}
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// 7. If image is not origin-clean, then set the CanvasRenderingContext2D's origin-clean flag to false.
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if (image_is_not_origin_clean(image))
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