88 lines
1.9 KiB
C
88 lines
1.9 KiB
C
#include <math.h>
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#include "pixman.h"
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#include "gtk-utils.h"
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static uint32_t
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linear_argb_to_premult_argb (float a,
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float r,
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float g,
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float b)
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{
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r *= a;
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g *= a;
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b *= a;
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return (uint32_t) (a * 255.0f + 0.5f) << 24
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| (uint32_t) (r * 255.0f + 0.5f) << 16
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| (uint32_t) (g * 255.0f + 0.5f) << 8
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| (uint32_t) (b * 255.0f + 0.5f) << 0;
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}
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static float
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lin2srgb (float linear)
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{
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if (linear < 0.0031308f)
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return linear * 12.92f;
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else
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return 1.055f * powf (linear, 1.0f/2.4f) - 0.055f;
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}
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static uint32_t
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linear_argb_to_premult_srgb_argb (float a,
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float r,
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float g,
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float b)
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{
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r = lin2srgb (r * a);
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g = lin2srgb (g * a);
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b = lin2srgb (b * a);
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return (uint32_t) (a * 255.0f + 0.5f) << 24
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| (uint32_t) (r * 255.0f + 0.5f) << 16
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| (uint32_t) (g * 255.0f + 0.5f) << 8
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| (uint32_t) (b * 255.0f + 0.5f) << 0;
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}
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int
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main (int argc, char **argv)
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{
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#define WIDTH 400
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#define HEIGHT 200
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int y, x, p;
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float alpha;
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uint32_t *dest = malloc (WIDTH * HEIGHT * 4);
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uint32_t *src1 = malloc (WIDTH * HEIGHT * 4);
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pixman_image_t *dest_img, *src1_img;
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dest_img = pixman_image_create_bits (PIXMAN_a8r8g8b8_sRGB,
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WIDTH, HEIGHT,
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dest,
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WIDTH * 4);
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src1_img = pixman_image_create_bits (PIXMAN_a8r8g8b8,
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WIDTH, HEIGHT,
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src1,
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WIDTH * 4);
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for (y = 0; y < HEIGHT; y ++)
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{
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p = WIDTH * y;
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for (x = 0; x < WIDTH; x ++)
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{
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alpha = (float) x / WIDTH;
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src1[p + x] = linear_argb_to_premult_argb (alpha, 1, 0, 1);
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dest[p + x] = linear_argb_to_premult_srgb_argb (1-alpha, 0, 1, 0);
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}
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}
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pixman_image_composite (PIXMAN_OP_ADD, src1_img, NULL, dest_img,
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0, 0, 0, 0, 0, 0, WIDTH, HEIGHT);
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pixman_image_unref (src1_img);
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free (src1);
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show_image (dest_img);
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pixman_image_unref (dest_img);
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free (dest);
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return 0;
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}
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