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gui_fader: precompute dithered 16x16 tile

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This improves the performance of the Alpha_dither_painter in
the run/gui_fader scenario by about 3x.
This commit is contained in:
Norman Feske 2025-01-28 12:52:37 +01:00 committed by Christian Helmuth
parent a5d3613f50
commit 146f161383
1 changed files with 27 additions and 13 deletions
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40
repos/gems/src/server/gui_fader/alpha_dither_painter.h
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@ -24,6 +24,28 @@ struct Alpha_dither_painter
using Pixel_alpha8 = Genode::Pixel_alpha8;
using Rect = Genode::Surface_base::Rect;
using Point = Genode::Surface_base::Point;
using uint8_t = Genode::uint8_t;
struct Alpha_tile_16x16
{
uint8_t v[256];
static Alpha_tile_16x16 from_fade_value(int fade)
{
using namespace Genode;
fade *= 256; /* scale fade value to range of alpha values */
Alpha_tile_16x16 t;
for (unsigned y = 0; y < 16; y++) {
for (unsigned x = 0; x < 16; x++) {
int const v = Dither_matrix::value(x, y) << 13;
t.v[y*16 + x] = (uint8_t)min(255, max(0, (fade - v) >> 16));
}
}
return t;
}
};
/*
* \param fade fade value in 16.16 fixpoint format
@ -39,23 +61,15 @@ struct Alpha_dither_painter
int y = clipped.y1();
/* scale fade value to range of alpha values */
fade *= 256;
Alpha_tile_16x16 const tile = Alpha_tile_16x16::from_fade_value(fade);
for (int w, h = clipped.h() ; h--; dst_line += surface.size().w) {
for (int w, h = clipped.h() ; h--; dst_line += surface.size().w, y++) {
int x = clipped.x1();
unsigned const y_offset = y << 4;
for (dst = dst_line, w = clipped.w(); w--; dst++, x++) {
using namespace Genode;
int const v = Dither_matrix::value(x, y) << 13;
dst->pixel = (uint8_t)min(255, max(0, (fade - v) >> 16));
}
y++;
for (dst = dst_line, w = clipped.w(); w--; dst++, x++)
dst->pixel = tile.v[(y_offset + x) & 0xff];
}
}