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LibWeb: Use box sampling instead of bilinear scaling when downscaling

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As a heuristic, either the width or height of the scaled image should
decrease for box sampling to be used. Otherwise, we use bilinear
scaling.
This commit is contained in:
Jelle Raaijmakers 2023-05-19 00:41:12 +02:00 • committed by Andreas Kling
parent fae9a05039
commit 7652dbd983
5 changed files with 13 additions and 6 deletions
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4
Userland/Libraries/LibWeb/CSS/ComputedValues.h
View file

@ -185,12 +185,14 @@ struct BorderRadiusData {
};
// FIXME: Find a better place for this helper.
inline Gfx::Painter::ScalingMode to_gfx_scaling_mode(CSS::ImageRendering css_value)
inline Gfx::Painter::ScalingMode to_gfx_scaling_mode(CSS::ImageRendering css_value, Gfx::IntRect source, Gfx::IntRect target)
{
switch (css_value) {
case CSS::ImageRendering::Auto:
case CSS::ImageRendering::HighQuality:
case CSS::ImageRendering::Smooth:
if (target.width() < source.width() || target.height() < source.height())
return Gfx::Painter::ScalingMode::BoxSampling;
return Gfx::Painter::ScalingMode::BilinearBlend;
case CSS::ImageRendering::CrispEdges:
return Gfx::Painter::ScalingMode::NearestNeighbor;

6
Userland/Libraries/LibWeb/CSS/StyleValues/ImageStyleValue.cpp
View file

@ -102,8 +102,10 @@ Optional<CSSPixels> ImageStyleValue::natural_height() const
void ImageStyleValue::paint(PaintContext& context, DevicePixelRect const& dest_rect, CSS::ImageRendering image_rendering) const
{
if (auto* b = bitmap(m_current_frame_index); b != nullptr)
context.painter().draw_scaled_bitmap(dest_rect.to_type<int>(), *b, bitmap(0)->rect(), 1.0f, to_gfx_scaling_mode(image_rendering));
if (auto* b = bitmap(m_current_frame_index); b != nullptr) {
auto scaling_mode = to_gfx_scaling_mode(image_rendering, bitmap(0)->rect(), dest_rect.to_type<int>());
context.painter().draw_scaled_bitmap(dest_rect.to_type<int>(), *b, bitmap(0)->rect(), 1.f, scaling_mode);
}
}
}