tinytga.c

// Tiny TGA writer: original code by jon olick, public domain
// Elder C version by rlyeh, public domain | wtrmrkrlyeh
#include <stdio.h>
static void tinytga(FILE *fp, void *rgba, int width, int height, int numChannels) {
    // Swap RGBA to BGRA if using 3 or more channels
    int x, i, y, j, bpc = numChannels * 8; // 8 bits per channel
    int remap[4] = {numChannels >= 3 ? 2 : 0, 1, numChannels >= 3 ? 0 : 2, 3};
    char *s = (char *)rgba;
    // Header
    fwrite("\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00", 12, 1, fp);
    fwrite(&width, 2, 1, fp);
    fwrite(&height, 2, 1, fp);
    fwrite(&bpc, 2, 1, fp);
    for(y = height-1; y >= 0; --y) {
        i = (y * width) * numChannels;
        for(x = i; x < i+width*numChannels; x += numChannels) {
            for(j = 0; j < numChannels; ++j) {
                fputc(s[x+remap[j]], fp);
            }
        }
    }
}