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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct {
unsigned char r, g, b, a;
} Colour;
int main(int argc, char** argv) {
FILE* outfile, * infile;
char bmp_magic[2];
int ret = 0;
unsigned bmp_offset;
int bmp_w, bmp_h, x, y, s, bs;
unsigned short bmp_bits;
unsigned* bitmap;
Colour pixel, * buffer;
unsigned char t;
if (argc < 3) {
fprintf(stderr, "Usage: %s infile outfile.\n", argv[0]);
return 1;
}
infile = fopen(argv[1], "rb");
if (!infile) {
fprintf(stderr, "Failed to open %s.\n", argv[1]);
return 2;
}
fread(bmp_magic, 2, 1, infile);
if (bmp_magic[0] != 'B' || bmp_magic[1] != 'M') {
ret = 3;
fprintf(stderr, "Not a valid bitmap file.\n");
goto end;
}
fseek(infile, 10, SEEK_SET);
fread(&bmp_offset, 4, 1, infile);
fseek(infile, 18, SEEK_SET);
fread(&bmp_w, 4, 1, infile);
fread(&bmp_h, 4, 1, infile);
fseek(infile, 28, SEEK_SET);
fread(&bmp_bits, 2, 1, infile);
if (bmp_bits != 32) {
ret = 4;
fprintf(stderr, "Bitmap must have 32 bit pixels. %d\n", bmp_bits);
goto end;
}
fseek(infile, bmp_offset, SEEK_SET);
s = bmp_w * bmp_h;
buffer = malloc(s * 4);
/* Read & flip */
for (y = 0; y < bmp_h; y++) {
for (x = 0; x < bmp_w; x++) {
fread(&pixel, 1, 4, infile);
t = pixel.r;
pixel.r = pixel.b;
pixel.b = t;
if (pixel.a == 0) {
pixel.r = 0;
pixel.g = 0;
pixel.b = 0;
}
buffer[x + (bmp_h - y - 1) * bmp_w] = pixel;
}
}
outfile = fopen(argv[2], "wb");
if (!outfile) {
fprintf(stderr, "Failed to open %s.\n", argv[2]);
fclose(infile);
return 2;
}
bs = (bmp_w * bmp_h + 32) / 32 * 4;
bitmap = calloc(bs, 1);
for (y = 0; y < bmp_h; y++) {
for (x = 0; x < bmp_w; x++) {
int idx = x + y * bmp_w;
if (buffer[idx].r) {
bitmap[idx / 32] |= 1 << (idx % 32);
}
}
}
fwrite(&bmp_w, 1, 2, outfile);
fwrite(&bmp_h, 1, 2, outfile);
fwrite(bitmap, 1, bs, outfile);
free(buffer);
end:
fclose(infile);
fclose(outfile);
return ret;
}
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