1 #include <math.h>
2
3 #include "pixman.h"
4 #include "gtk-utils.h"
5
6 static uint32_t
linear_argb_to_premult_argb(float a,float r,float g,float b)7 linear_argb_to_premult_argb (float a,
8 float r,
9 float g,
10 float b)
11 {
12 r *= a;
13 g *= a;
14 b *= a;
15 return (uint32_t) (a * 255.0f + 0.5f) << 24
16 | (uint32_t) (r * 255.0f + 0.5f) << 16
17 | (uint32_t) (g * 255.0f + 0.5f) << 8
18 | (uint32_t) (b * 255.0f + 0.5f) << 0;
19 }
20
21 static float
lin2srgb(float linear)22 lin2srgb (float linear)
23 {
24 if (linear < 0.0031308f)
25 return linear * 12.92f;
26 else
27 return 1.055f * powf (linear, 1.0f/2.4f) - 0.055f;
28 }
29
30 static uint32_t
linear_argb_to_premult_srgb_argb(float a,float r,float g,float b)31 linear_argb_to_premult_srgb_argb (float a,
32 float r,
33 float g,
34 float b)
35 {
36 r = lin2srgb (r * a);
37 g = lin2srgb (g * a);
38 b = lin2srgb (b * a);
39 return (uint32_t) (a * 255.0f + 0.5f) << 24
40 | (uint32_t) (r * 255.0f + 0.5f) << 16
41 | (uint32_t) (g * 255.0f + 0.5f) << 8
42 | (uint32_t) (b * 255.0f + 0.5f) << 0;
43 }
44
45 int
main(int argc,char ** argv)46 main (int argc, char **argv)
47 {
48 #define WIDTH 400
49 #define HEIGHT 200
50 int y, x, p;
51 float alpha;
52
53 uint32_t *dest = malloc (WIDTH * HEIGHT * 4);
54 uint32_t *src1 = malloc (WIDTH * HEIGHT * 4);
55 pixman_image_t *dest_img, *src1_img;
56
57 dest_img = pixman_image_create_bits (PIXMAN_a8r8g8b8_sRGB,
58 WIDTH, HEIGHT,
59 dest,
60 WIDTH * 4);
61 src1_img = pixman_image_create_bits (PIXMAN_a8r8g8b8,
62 WIDTH, HEIGHT,
63 src1,
64 WIDTH * 4);
65
66 for (y = 0; y < HEIGHT; y ++)
67 {
68 p = WIDTH * y;
69 for (x = 0; x < WIDTH; x ++)
70 {
71 alpha = (float) x / WIDTH;
72 src1[p + x] = linear_argb_to_premult_argb (alpha, 1, 0, 1);
73 dest[p + x] = linear_argb_to_premult_srgb_argb (1-alpha, 0, 1, 0);
74 }
75 }
76
77 pixman_image_composite (PIXMAN_OP_ADD, src1_img, NULL, dest_img,
78 0, 0, 0, 0, 0, 0, WIDTH, HEIGHT);
79 pixman_image_unref (src1_img);
80 free (src1);
81
82 show_image (dest_img);
83 pixman_image_unref (dest_img);
84 free (dest);
85
86 return 0;
87 }
88