vorbis_ca.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define B 4

static unsigned char* ntb(unsigned char b[], unsigned int n) {
    b[0] = n >> 24;
    b[1] = n >> 16;
    b[2] = n >> 8;
    b[3] = n;
    return b;
}

int main(int argc, char *argv[]) {
    if (argc < 4) {
        fprintf(stderr, "Usage: %s width height image_file\n", argv[0]);
        exit(1);
    }

    unsigned char b[4];
    int pic_type = 3; // Cover (front);
    fwrite(ntb(b, pic_type), B, 1, stdout);
    char mime_type[] = "image/jpg";
    int mt_len = strlen(mime_type);
    fwrite(ntb(b, mt_len), B, 1, stdout);
    fwrite(mime_type, mt_len, 1, stdout);
    fwrite(ntb(b, 0), B, 1, stdout); // description length (= 0)
    fwrite(ntb(b, atoi(argv[1])), B, 1, stdout); // width
    fwrite(ntb(b, atoi(argv[2])), B, 1, stdout); // height
    fwrite(ntb(b, 24), B, 1, stdout); // color depth in bits-per-pixel
    fwrite(ntb(b, 0), B, 1, stdout); // non-indexed picture

    FILE* image = fopen(argv[3], "rb");
    if (!image) {
        fprintf(stderr, "cannot open image file\n");
        exit(1);
    }

    fseek(image, 0, SEEK_END);
    int file_size = ftell(image);

    fwrite(ntb(b, file_size), B, 1, stdout);
}