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Sped up conversion from Pango surface to SDL surface.

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(Reference compiler: gcc 4.3 on amd64.)
This commit is contained in:
Guillaume Melquiond 2009-10-10 09:36:39 +00:00
parent 56fda937be
commit c56050dda1
1 changed files with 43 additions and 33 deletions
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76
src/text.cpp
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@ -449,21 +449,49 @@ void ttext::recalculate(const bool force) const
}
}
/**
* Helper function to decode pixels.
*
* @param alpha The value of the alpha channel, this value
* must not be zero.
* @param sub_pixel The address of a sub pixel, either red,
* green or blue.
*/
static void decode_pixel(const unsigned char alpha, unsigned char *sub_pixel)
struct decode_table
{
unsigned colour = *sub_pixel;
// Saturate at 255.
*sub_pixel = colour >= alpha
? 255
: static_cast<unsigned char>((colour << 8) / alpha);
// 1-based, from 1 to 255.
unsigned values[255];
decode_table()
{
for (int i = 1; i < 256; ++i) values[i - 1] = (255 * 256) / i;
}
};
static decode_table decode_table;
/**
* Converts from premultiplied alpha to plain alpha.
* @param p pointer to a 4-byte endian-dependent color.
*/
static void decode_pixel(unsigned char *p)
{
// Assume everything not compiled with gcc to be on a little endian platform.
#if defined(__GNUC__) && defined(__BIG_ENDIAN__)
int alpha = p[0];
#else
int alpha = p[3];
#endif
if (alpha == 0) return;
int div = decode_table.values[alpha - 1];
#define DECODE(i) \
do { \
unsigned color = p[i]; \
color = color * div / 256; \
if (color > 255) color = 255; \
p[i] = color; \
} while (0)
#if defined(__GNUC__) && defined(__BIG_ENDIAN__)
DECODE(3);
#else
DECODE(0);
#endif
DECODE(1);
DECODE(2);
}
void ttext::rerender(const bool force) const
@ -504,25 +532,7 @@ void ttext::rerender(const bool force) const
for (int x = 0; x < width; ++x)
{
unsigned char *pixel = &surface_buffer_[(y * width + x) * 4];
// Assume everything not compiled with gcc to be on a little endian platform.
#if defined(__GNUC__) && defined(__BIG_ENDIAN__)
const unsigned char alpha = *(pixel + 0);
#else
const unsigned char alpha = *(pixel + 3);
#endif
if(alpha == 0) {
continue;
}
// Assume everything not compiled with gcc to be on a little endian platform.
#if defined(__GNUC__) && defined(__BIG_ENDIAN__)
decode_pixel(alpha, pixel + 3);
#else
decode_pixel(alpha, pixel + 0);
#endif
decode_pixel(alpha, pixel + 1);
decode_pixel(alpha, pixel + 2);
decode_pixel(pixel);
}
}
#else