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LibGfx: Enable Painter::blit to apply opacity and mix alpha channels

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This enables us to properly render windows that use both opacity and
alpha channels.
This commit is contained in:
Tom 2021-02-13 11:10:27 -07:00 committed by Andreas Kling
parent 9ce0639383
commit ddbd88d5c6
Notes: sideshowbarker 2024-07-18 22:21:16 +09:00 
Author: https://github.com/tomuta
Commit: https://github.com/SerenityOS/serenity/commit/ddbd88d5c6e
Pull-request: https://github.com/SerenityOS/serenity/pull/5331
2 changed files with 26 additions and 65 deletions
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88
Userland/Libraries/LibGfx/Painter.cpp
View file

@ -522,14 +522,11 @@ void Painter::draw_triangle(const IntPoint& a, const IntPoint& b, const IntPoint
}
}
void Painter::blit_with_opacity(const IntPoint& position, const Gfx::Bitmap& source, const IntRect& a_src_rect, float opacity)
void Painter::blit_with_opacity(const IntPoint& position, const Gfx::Bitmap& source, const IntRect& a_src_rect, float opacity, bool apply_alpha)
{
ASSERT(scale() >= source.scale() && "painter doesn't support downsampling scale factors");
ASSERT(!m_target->has_alpha_channel());
if (!opacity)
return;
if (opacity >= 1.0f)
if (opacity >= 1.0f && !(source.has_alpha_channel() && apply_alpha))
return blit(position, source, a_src_rect);
u8 alpha = 255 * opacity;
@ -558,18 +555,28 @@ void Painter::blit_with_opacity(const IntPoint& position, const Gfx::Bitmap& sou
const RGBA32* src = source.scanline(src_rect.top() + first_row) + src_rect.left() + first_column;
const unsigned src_skip = source.pitch() / sizeof(RGBA32);
// FIXME: This does the wrong thing if source has an alpha channel: It ignores it and pretends that every pixel in source is fully opaque.
// Maybe just punt to draw_scaled_bitmap() in that case too?
for (int row = first_row; row <= last_row; ++row) {
for (int x = 0; x <= (last_column - first_column); ++x) {
Color src_color_with_alpha = Color::from_rgb(src[x]);
src_color_with_alpha.set_alpha(alpha);
Color dst_color = Color::from_rgb(dst[x]);
dst[x] = dst_color.blend(src_color_with_alpha).value();
auto do_blit = [&]<bool with_src_alpha>() {
for (int row = first_row; row <= last_row; ++row) {
for (int x = 0; x <= (last_column - first_column); ++x) {
if constexpr (with_src_alpha) {
Color src_color_with_alpha = Color::from_rgba(src[x]);
float pixel_opacity = src_color_with_alpha.alpha() / 255.0;
src_color_with_alpha.set_alpha(255 * (opacity * pixel_opacity));
dst[x] = Color::from_rgba(dst[x]).blend(src_color_with_alpha).value();
} else {
Color src_color_with_alpha = Color::from_rgb(src[x]);
src_color_with_alpha.set_alpha(alpha);
dst[x] = Color::from_rgb(dst[x]).blend(src_color_with_alpha).value();
}
}
dst += dst_skip;
src += src_skip;
}
dst += dst_skip;
src += src_skip;
}
};
if (source.has_alpha_channel() && apply_alpha)
do_blit.template operator()<true>();
else
do_blit.template operator()<false>();
}
void Painter::blit_filtered(const IntPoint& position, const Gfx::Bitmap& source, const IntRect& src_rect, Function<Color(Color)> filter)
@ -712,57 +719,12 @@ void Painter::blit_offset(const IntPoint& a_position, const Gfx::Bitmap& source,
blit(position, source, src_rect);
}
void Painter::blit_with_alpha(const IntPoint& position, const Gfx::Bitmap& source, const IntRect& a_src_rect)
{
auto safe_src_rect = a_src_rect.intersected(source.rect());
if (scale() != source.scale())
return draw_scaled_bitmap({ position, safe_src_rect.size() }, source, safe_src_rect);
ASSERT(source.has_alpha_channel());
auto dst_rect = IntRect(position, safe_src_rect.size()).translated(translation());
auto clipped_rect = dst_rect.intersected(clip_rect());
if (clipped_rect.is_empty())
return;
int scale = this->scale();
auto src_rect = a_src_rect * scale;
clipped_rect *= scale;
dst_rect *= scale;
const int first_row = clipped_rect.top() - dst_rect.top();
const int last_row = clipped_rect.bottom() - dst_rect.top();
const int first_column = clipped_rect.left() - dst_rect.left();
const int last_column = clipped_rect.right() - dst_rect.left();
RGBA32* dst = m_target->scanline(clipped_rect.y()) + clipped_rect.x();
const RGBA32* src = source.scanline(src_rect.top() + first_row) + src_rect.left() + first_column;
const size_t dst_skip = m_target->pitch() / sizeof(RGBA32);
const size_t src_skip = source.pitch() / sizeof(RGBA32);
for (int row = first_row; row <= last_row; ++row) {
for (int x = 0; x <= (last_column - first_column); ++x) {
u8 alpha = Color::from_rgba(src[x]).alpha();
if (alpha == 0xff)
dst[x] = src[x];
else if (!alpha)
continue;
else
dst[x] = Color::from_rgba(dst[x]).blend(Color::from_rgba(src[x])).value();
}
dst += dst_skip;
src += src_skip;
}
}
void Painter::blit(const IntPoint& position, const Gfx::Bitmap& source, const IntRect& a_src_rect, float opacity, bool apply_alpha)
{
ASSERT(scale() >= source.scale() && "painter doesn't support downsampling scale factors");
if (opacity < 1.0f)
return blit_with_opacity(position, source, a_src_rect, opacity);
if (source.has_alpha_channel() && apply_alpha)
return blit_with_alpha(position, source, a_src_rect);
if (opacity < 1.0f || (source.has_alpha_channel() && apply_alpha))
return blit_with_opacity(position, source, a_src_rect, opacity, apply_alpha);
auto safe_src_rect = a_src_rect.intersected(source.rect());
if (scale() != source.scale())

3
Userland/Libraries/LibGfx/Painter.h
View file

@ -137,8 +137,7 @@ protected:
void set_physical_pixel_with_draw_op(u32& pixel, const Color&);
void fill_physical_scanline_with_draw_op(int y, int x, int width, const Color& color);
void fill_rect_with_draw_op(const IntRect&, Color);
void blit_with_alpha(const IntPoint&, const Gfx::Bitmap&, const IntRect& src_rect);
void blit_with_opacity(const IntPoint&, const Gfx::Bitmap&, const IntRect& src_rect, float opacity);
void blit_with_opacity(const IntPoint&, const Gfx::Bitmap&, const IntRect& src_rect, float opacity, bool apply_alpha = true);
void draw_physical_pixel(const IntPoint&, Color, int thickness = 1);
IntRect clip_rect() const { return state().clip_rect; }