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#include <math.h>
#include "pixman.h"
#include "gtk-utils.h"
static uint32_t
linear_argb_to_premult_argb (float a,
float r,
float g,
float b)
{
r *= a;
g *= a;
b *= a;
return (uint32_t) (a * 255.0f + 0.5f) << 24
| (uint32_t) (r * 255.0f + 0.5f) << 16
| (uint32_t) (g * 255.0f + 0.5f) << 8
| (uint32_t) (b * 255.0f + 0.5f) << 0;
}
static float
lin2srgb (float linear)
{
if (linear < 0.0031308f)
return linear * 12.92f;
else
return 1.055f * powf (linear, 1.0f/2.4f) - 0.055f;
}
static uint32_t
linear_argb_to_premult_srgb_argb (float a,
float r,
float g,
float b)
{
r = lin2srgb (r * a);
g = lin2srgb (g * a);
b = lin2srgb (b * a);
return (uint32_t) (a * 255.0f + 0.5f) << 24
| (uint32_t) (r * 255.0f + 0.5f) << 16
| (uint32_t) (g * 255.0f + 0.5f) << 8
| (uint32_t) (b * 255.0f + 0.5f) << 0;
}
int
main (int argc, char **argv)
{
#define WIDTH 400
#define HEIGHT 200
int y, x, p;
float alpha;
uint32_t *dest = malloc (WIDTH * HEIGHT * 4);
uint32_t *src1 = malloc (WIDTH * HEIGHT * 4);
pixman_image_t *dest_img, *src1_img;
dest_img = pixman_image_create_bits (PIXMAN_a8r8g8b8_sRGB,
WIDTH, HEIGHT,
dest,
WIDTH * 4);
src1_img = pixman_image_create_bits (PIXMAN_a8r8g8b8,
WIDTH, HEIGHT,
src1,
WIDTH * 4);
for (y = 0; y < HEIGHT; y ++)
{
p = WIDTH * y;
for (x = 0; x < WIDTH; x ++)
{
alpha = (float) x / WIDTH;
src1[p + x] = linear_argb_to_premult_argb (alpha, 1, 0, 1);
dest[p + x] = linear_argb_to_premult_srgb_argb (1-alpha, 0, 1, 0);
}
}
pixman_image_composite (PIXMAN_OP_ADD, src1_img, NULL, dest_img,
0, 0, 0, 0, 0, 0, WIDTH, HEIGHT);
pixman_image_unref (src1_img);
free (src1);
pixman_image_unref (dest_img);
/* Now that the picture has been correctly constructed,
* we hand it over to our support library as argb which it
* knows how to handle (it doesn't understand _sRGB format). */
dest_img = pixman_image_create_bits (PIXMAN_a8r8g8b8,
WIDTH, HEIGHT,
dest,
WIDTH * 4);
show_image (dest_img);
pixman_image_unref (dest_img);
free (dest);
return 0;
}
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