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#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <cairo.h>
#define CLAMP(x, l, h) (((x) > (h)) ? (h) : (((x) < (l)) ? (l) : (x)))
static inline double
cos4(double x)
{
return CLAMP(pow(cos(x), 4.0), 0.001, 1.0);
}
int
main(int argc, char *argv[])
{
cairo_surface_t *s;
unsigned char *row, *p;
int x, y, i, width, height, stride;
if (argc < 2)
exit(EXIT_FAILURE);
s = cairo_image_surface_create_from_png(argv[1]);
if (!s || cairo_surface_status(s) != CAIRO_STATUS_SUCCESS)
exit(EXIT_FAILURE);
row = cairo_image_surface_get_data(s);
width = cairo_image_surface_get_width(s);
height = cairo_image_surface_get_height(s);
stride = cairo_image_surface_get_stride(s);
for (y = 0; y < height; ++y, row += stride) {
for (x = 0, p = row; x < width; ++x, p += 4) {
double c = 1.0 / cos4(1.2 * (x - width / 2) / width);
for (i = 0; i < 3; ++i)
p[i] = CLAMP(c * p[i], 0, 255);
}
}
cairo_surface_write_to_png(s, argc > 2 ? argv[2] : "unvignetted.png");
cairo_surface_destroy(s);
return 0;
}
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