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LibGfx: Make draw_scaled_bitmap() apply relative opacity

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Instead of overriding the alpha value of all source pixels, apply the
override opacity by multiplying with the source alpha.

Fixes #3004.
This commit is contained in:
Andreas Kling 2020-08-05 14:40:11 +02:00
parent f3cbb79f80
commit 00fe4c7bcb
1 changed files with 6 additions and 5 deletions
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11
Libraries/LibGfx/Painter.cpp
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@ -691,12 +691,13 @@ void Painter::blit(const IntPoint& position, const Gfx::Bitmap& source, const In
template<bool has_alpha_channel, typename GetPixel>
ALWAYS_INLINE static void do_draw_integer_scaled_bitmap(Gfx::Bitmap& target, const IntRect& dst_rect, const Gfx::Bitmap& source, int hfactor, int vfactor, GetPixel get_pixel, float opacity)
{
u8 src_alpha = opacity * 255;
bool has_opacity = opacity != 1.0f;
for (int y = source.rect().top(); y <= source.rect().bottom(); ++y) {
int dst_y = dst_rect.y() + y * vfactor;
for (int x = source.rect().left(); x <= source.rect().right(); ++x) {
auto src_pixel = get_pixel(source, x, y);
src_pixel.set_alpha(src_alpha);
if (has_opacity)
src_pixel.set_alpha(src_pixel.alpha() * opacity);
for (int yo = 0; yo < vfactor; ++yo) {
auto* scanline = (Color*)target.scanline(dst_y + yo);
int dst_x = dst_rect.x() + x * hfactor;
@ -726,7 +727,7 @@ ALWAYS_INLINE static void do_draw_scaled_bitmap(Gfx::Bitmap& target, const IntRe
return do_draw_integer_scaled_bitmap<has_alpha_channel>(target, dst_rect, source, hfactor, vfactor, get_pixel, opacity);
}
u8 src_alpha = opacity * 255;
bool has_opacity = opacity != 1.0f;
for (int y = clipped_rect.top(); y <= clipped_rect.bottom(); ++y) {
auto* scanline = (Color*)target.scanline(y);
@ -734,8 +735,8 @@ ALWAYS_INLINE static void do_draw_scaled_bitmap(Gfx::Bitmap& target, const IntRe
auto scaled_x = ((x - dst_rect.x()) * hscale) >> 16;
auto scaled_y = ((y - dst_rect.y()) * vscale) >> 16;
auto src_pixel = get_pixel(source, scaled_x, scaled_y);
src_pixel.set_alpha(src_alpha);
if (has_opacity)
src_pixel.set_alpha(src_pixel.alpha() * opacity);
if constexpr (has_alpha_channel) {
scanline[x] = scanline[x].blend(src_pixel);
} else