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gdk: Specialise RGBA8 → premultiplied BGRA8 conversion

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On x86 on a Kaby Lake CPU, this makes it go from 6.63% of the total
execution time (loading some PNGs using the cairo backend) down to
3.20%.

On ARM on a Cortex-A7, on the same workload, this makes it go from 57%
to 8.36%.
This commit is contained in:
Emmanuel Gil Peyrot 2022-02-15 20:54:18 +01:00
parent 82e4690564
commit 0e3ed7a738
1 changed files with 34 additions and 0 deletions
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34
gdk/gdkmemoryformat.c
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@ -166,6 +166,29 @@ r32g32b32a32_float_from_float (guchar *dest,
memcpy (dest, src, sizeof (float) * n * 4);
}
// This one conversion is quite important, it converts from RGBA with straight
// alpha (as found in PNG for instance) to BGRA with premultiplied alpha (the
// sole cairo format available).
static void
r8g8b8a8_to_b8g8r8a8_premultiplied (guchar *dest,
const guchar *src,
gsize n)
{
for (; n > 0; n--)
{
guchar a = src[3];
guint16 r = (guint16)src[0] * a + 127;
guint16 g = (guint16)src[1] * a + 127;
guint16 b = (guint16)src[2] * a + 127;
dest[0] = (b + (b >> 8) + 1) >> 8;
dest[1] = (g + (g >> 8) + 1) >> 8;
dest[2] = (r + (r >> 8) + 1) >> 8;
dest[3] = a;
dest += 4;
src += 4;
}
}
struct _GdkMemoryFormatDescription
{
GdkMemoryAlpha alpha;
@ -479,6 +502,17 @@ gdk_memory_convert (guchar *dest_data,
g_assert (dest_format < GDK_MEMORY_N_FORMATS);
g_assert (src_format < GDK_MEMORY_N_FORMATS);
if (src_format == GDK_MEMORY_R8G8B8A8 && dest_format == GDK_MEMORY_B8G8R8A8_PREMULTIPLIED)
{
for (y = 0; y < height; y++)
{
r8g8b8a8_to_b8g8r8a8_premultiplied (dest_data, src_data, width);
src_data += src_stride;
dest_data += dest_stride;
}
return;
}
tmp = g_new (float, width * 4);
for (y = 0; y < height; y++)