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PNGLoader: Reduce unfiltering branchiness even more.

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Use a dummy scanline for y=0 filled with all zeroes to avoid having to check
y on every iteration before grabbing color data from scanline[y - 1].
This commit is contained in:
Andreas Kling 2019-03-21 16:55:31 +01:00
parent cd1afde48c
commit 796bc56a13
Notes: sideshowbarker 2024-07-19 14:58:41 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/796bc56a13a
1 changed files with 22 additions and 17 deletions
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39
SharedGraphics/PNGLoader.cpp
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@ -162,8 +162,9 @@ union [[gnu::packed]] Pixel {
static_assert(sizeof(Pixel) == 4);
template<bool has_alpha, byte filter_type>
[[gnu::always_inline]] static inline void unfilter_impl(const GraphicsBitmap& bitmap, int y)
[[gnu::always_inline]] static inline void unfilter_impl(const GraphicsBitmap& bitmap, int y, const void* dummy_scanline_data)
{
auto* dummy_scanline = (const Pixel*)dummy_scanline_data;
if constexpr (filter_type == 1) {
auto* pixels = (Pixel*)bitmap.scanline(y);
for (int i = 0; i < bitmap.width(); ++i) {
@ -181,11 +182,12 @@ template<bool has_alpha, byte filter_type>
}
if constexpr (filter_type == 2) {
auto* pixels = (Pixel*)bitmap.scanline(y);
auto* pixels_y_minus_1 = y == 0 ? dummy_scanline : (Pixel*)bitmap.scanline(y - 1);
for (int i = 0; i < bitmap.width(); ++i) {
auto& x = pixels[i];
swap(x.r, x.b);
Pixel b;
if (y != 0) b.rgba = bitmap.scanline(y - 1)[i];
b.rgba = pixels_y_minus_1[i].rgba;
x.r += b.r;
x.g += b.g;
x.b += b.b;
@ -197,13 +199,14 @@ template<bool has_alpha, byte filter_type>
if constexpr (filter_type == 3) {
auto* pixels = (Pixel*)bitmap.scanline(y);
auto* pixels_y_minus_1 = y == 0 ? dummy_scanline : (Pixel*)bitmap.scanline(y - 1);
for (int i = 0; i < bitmap.width(); ++i) {
auto& x = pixels[i];
swap(x.r, x.b);
Pixel a;
Pixel b;
if (i != 0) a.rgba = bitmap.scanline(y)[i - 1];
if (y != 0) b.rgba = bitmap.scanline(y - 1)[i];
b.rgba = pixels_y_minus_1[i].rgba;
x.r = x.r + ((a.r + b.r) / 2);
x.g = x.g + ((a.g + b.g) / 2);
x.b = x.b + ((a.b + b.b) / 2);
@ -215,15 +218,18 @@ template<bool has_alpha, byte filter_type>
if constexpr (filter_type == 4) {
auto* pixels = (Pixel*)bitmap.scanline(y);
auto* pixels_y_minus_1 = y == 0 ? dummy_scanline : (Pixel*)bitmap.scanline(y - 1);
for (int i = 0; i < bitmap.width(); ++i) {
auto& x = pixels[i];
swap(x.r, x.b);
Pixel a;
Pixel b;
Pixel c;
if (i != 0) a.rgba = bitmap.scanline(y)[i - 1];
if (y != 0) b.rgba = bitmap.scanline(y - 1)[i];
if (y != 0 && i != 0) c.rgba = bitmap.scanline(y - 1)[i - 1];
if (i != 0) {
a.rgba = bitmap.scanline(y)[i - 1];
c.rgba = pixels_y_minus_1[i - 1].rgba;
}
b.rgba = pixels_y_minus_1[i].rgba;
x.r += paeth_predictor(a.r, b.r, c.r);
x.g += paeth_predictor(a.g, b.g, c.g);
x.b += paeth_predictor(a.b, b.b, c.b);
@ -233,9 +239,6 @@ template<bool has_alpha, byte filter_type>
}
}
[[gnu::noinline]] static void unfilter(PNGLoadingContext& context)
{
{
@ -266,6 +269,8 @@ template<bool has_alpha, byte filter_type>
}
}
auto dummy_scanline = ByteBuffer::create_zeroed(context.width * sizeof(RGBA32));
Stopwatch sw("load_png_impl: unfilter: process");
for (int y = 0; y < context.height; ++y) {
auto filter = context.scanlines[y].filter;
@ -273,30 +278,30 @@ template<bool has_alpha, byte filter_type>
continue;
if (filter == 1) {
if (context.has_alpha())
unfilter_impl<true, 1>(*context.bitmap, y);
unfilter_impl<true, 1>(*context.bitmap, y, dummy_scanline.pointer());
else
unfilter_impl<false, 1>(*context.bitmap, y);
unfilter_impl<false, 1>(*context.bitmap, y, dummy_scanline.pointer());
continue;
}
if (filter == 2) {
if (context.has_alpha())
unfilter_impl<true, 2>(*context.bitmap, y);
unfilter_impl<true, 2>(*context.bitmap, y, dummy_scanline.pointer());
else
unfilter_impl<false, 2>(*context.bitmap, y);
unfilter_impl<false, 2>(*context.bitmap, y, dummy_scanline.pointer());
continue;
}
if (filter == 3) {
if (context.has_alpha())
unfilter_impl<true, 3>(*context.bitmap, y);
unfilter_impl<true, 3>(*context.bitmap, y, dummy_scanline.pointer());
else
unfilter_impl<false, 3>(*context.bitmap, y);
unfilter_impl<false, 3>(*context.bitmap, y, dummy_scanline.pointer());
continue;
}
if (filter == 4) {
if (context.has_alpha())
unfilter_impl<true, 4>(*context.bitmap, y);
unfilter_impl<true, 4>(*context.bitmap, y, dummy_scanline.pointer());
else
unfilter_impl<false, 4>(*context.bitmap, y);
unfilter_impl<false, 4>(*context.bitmap, y, dummy_scanline.pointer());
continue;
}
}