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#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"
#include <stdio.h>
#define TSIZE 8
#define RGB(r, g, b) (((r) << 11) | ((g) << 5) | (b))
static void
output_tile(const uint8_t *data, int x, int y, int w)
{
for (int iy = 0; iy < TSIZE; iy += 1) {
putchar('\t');
for (int ix = 0; ix < TSIZE; ix += 1) {
const int i = (ix + x + (iy + y) * w) * 3;
const int v = RGB(data[i]/8, data[i+1]/4, data[i+2]/8);
printf("%04x ", v);
}
putchar('\n');
}
}
int
main(int argc, char **argv)
{
if (argc != 1) {
fprintf(stderr, "usage: %s < tileset.png\n", argv[0]);
return 1;
}
/* Load image. */
int w, h, chans;
uint8_t *const data = stbi_load_from_file(stdin, &w, &h, &chans, 3);
if (data == NULL) {
fprintf(stderr, "stbi_load_from_file failed\n");
return 1;
}
if (w % TSIZE || h % TSIZE) {
fprintf(stderr, "invalid dimensions %dx%d, "
"expected dimensions divisible by %d\n",
w, h, TSIZE);
goto panic;
}
if (chans != 3) {
fprintf(stderr, "my lame utility only supports "
"images using 3 color channels, "
"yours has %d channels. too bad\n", chans);
goto panic;
}
for (int y = 0; y < h; y += TSIZE)
for (int x = 0; x < w; x += TSIZE)
output_tile(data, x, y, w);
stbi_image_free(data);
return 0;
panic:
stbi_image_free(data);
return 0;
}
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