bmp file reader and diff computation pixel by pixel

image_diff.c

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdint.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <string.h>

#define memcpy_lol(_dst, _src, _size, _loc) {\
    memcpy(_dst, _src, _size);\
    (_loc) = (uint8_t *)((uint8_t *)_src + (size_t)_size);\
}

#define memcpy_ultra(_dst_noptr, _src, _loc) memcpy_lol(&_dst_noptr, _src, sizeof _dst_noptr, _loc)

struct rgb_s {
    uint8_t red;
    uint8_t green;
    uint8_t blue;
};

struct bmp_s {
    struct header_s {
        uint8_t id[2];
        uint32_t size;
        uint16_t _reserved0;
        uint16_t _reserved1;
        uint32_t offset;
    } header;

    struct dip_s {
        uint16_t width;
        uint16_t heigth;
    } dip;

    struct rgb_s *pixels;
};

typedef union {
    uint8_t byte;
    struct {
        unsigned red: 1;
        unsigned green: 1;
        unsigned blue: 1;
        unsigned _reserved: 5;
    } channels;
} diffsign_t;

void read_bmp(struct bmp_s *bmp, const char *bmpfile) {
    int fd, i;
    struct stat sb;
    uint8_t *file;
    uint8_t *bmap;

    lstat(bmpfile, &sb);
    file = malloc(sb.st_size * sizeof *file);
    fd = open(bmpfile, O_RDONLY);

    if (read(fd, file, sb.st_size * sizeof *file) != sb.st_size) {
        fprintf(stderr, "WTF!\n");
    }

    memcpy(bmp->header.id, file + 0x00, 2 * sizeof *bmp->header.id);
    memcpy(&bmp->header.size, file + 0x02, sizeof bmp->header.size);
    memcpy(&bmp->header.offset, file + 0x0a, sizeof bmp->header.offset);
    memcpy(&bmp->dip.width, file + 0x12, sizeof bmp->dip.width);
    memcpy(&bmp->dip.heigth, file + 0x16, sizeof bmp->dip.heigth);
    
    bmap = malloc(bmp->header.size * sizeof *bmap);
    memcpy(bmap, file + bmp->header.offset, bmp->header.size * sizeof *bmap);

    bmp->pixels = malloc((bmp->header.size / 3) * sizeof *bmp->pixels);
    for (i = 0; i < bmp->dip.heigth * bmp->dip.width; i++) {
        bmp->pixels[i].red = bmap[3 * i + 2];
        bmp->pixels[i].green = bmap[3 * i + 1];
        bmp->pixels[i].blue = bmap[3 * i + 0];
    }

    free(bmap);
    free(file);
    close(fd);
}

int main(int argc, char **argv) {
    struct bmp_s bmp1, bmp2;
    int i, j, max;
    struct rgb_s *diff;
    diffsign_t *diffsign;

    if (argc < 3) {
        fprintf(stderr, "ERROR: no image specified!\n");
    }

    read_bmp(&bmp1, argv[1]);
    read_bmp(&bmp2, argv[2]);

    diff = malloc(bmp1.dip.heigth * bmp1.dip.width * sizeof *diff);
    diffsign = malloc(bmp1.dip.heigth * bmp1.dip.width * sizeof *diffsign);

    // for (i = 0, max = bmp1.dip.heigth * bmp1.dip.width; i < max; i++) {
    //     diff[i].red = abs(bmp2.pixels[i].red - bmp1.pixels[i].red);
    //     diff[i].green = abs(bmp2.pixels[i].green - bmp1.pixels[i].green);
    //     diff[i].blue = abs(bmp2.pixels[i].blue - bmp1.pixels[i].blue);

    //     diffsign[i].channels.red = bmp2.pixels[i].red < bmp1.pixels[i].red;
    //     diffsign[i].channels.green = bmp2.pixels[i].green < bmp1.pixels[i].green;
    //     diffsign[i].channels.blue = bmp2.pixels[i].blue < bmp1.pixels[i].blue;

    //     // if (diff[i].red || diff[i].green || diff[i].blue) {
    //     //     printf("\tbmp1 [%04d][%04d] r: %03d g: %03d b: %03d\n", i / bmp1.dip.width, j % bmp1.dip.width, bmp1.pixels[i].red, bmp1.pixels[i].green, bmp1.pixels[i].blue);
    //     //     printf("\tbmp2 [%04d][%04d] r: %03d g: %03d b: %03d\n", i / bmp1.dip.width, j % bmp1.dip.width, bmp2.pixels[i].red, bmp2.pixels[i].green, bmp2.pixels[i].blue);
    //     //     printf("\tdiff [%04d][%04d] r: %03d g: %03d b: %03d\n", i / bmp1.dip.width, j % bmp1.dip.width, diff[i].red, diff[i].green, diff[i].blue);
    //     //     printf("\tsign [%04d][%04d] r: %03d g: %03d b: %03d\n", i / bmp1.dip.width, j % bmp1.dip.width, diffsign[i].channels.red, diffsign[i].channels.green, diffsign[i].channels.blue);
    //     //     printf("\n");
    //     // }
    // }

    for (i = 0; i < bmp1.dip.heigth; i++) {
        for (j = 0; j < bmp1.dip.width; j++) {
            diff[i * bmp1.dip.width + j].red = abs(bmp2.pixels[i * bmp1.dip.width + j].red - bmp1.pixels[i * bmp1.dip.width + j].red);
            diff[i * bmp1.dip.width + j].green = abs(bmp2.pixels[i * bmp1.dip.width + j].green - bmp1.pixels[i * bmp1.dip.width + j].green);
            diff[i * bmp1.dip.width + j].blue = abs(bmp2.pixels[i * bmp1.dip.width + j].blue - bmp1.pixels[i * bmp1.dip.width + j].blue);

            diffsign[i * bmp1.dip.width + j].channels.red = bmp2.pixels[i * bmp1.dip.width + j].red < bmp1.pixels[i * bmp1.dip.width + j].red;
            diffsign[i * bmp1.dip.width + j].channels.green = bmp2.pixels[i * bmp1.dip.width + j].green < bmp1.pixels[i * bmp1.dip.width + j].green;
            diffsign[i * bmp1.dip.width + j].channels.blue = bmp2.pixels[i * bmp1.dip.width + j].blue < bmp1.pixels[i * bmp1.dip.width + j].blue;

            // if (diff[i * bmp1.dip.width + j].red || diff[i * bmp1.dip.width + j].green || diff[i * bmp1.dip.width + j].blue) {
            //     printf("\tbmp1 [%04d][%04d] r: %03d g: %03d b: %03d\n", i, j, bmp1.pixels[i * bmp1.dip.width + j].red, bmp1.pixels[i * bmp1.dip.width + j].green, bmp1.pixels[i * bmp1.dip.width + j].blue);
            //     printf("\tbmp2 [%04d][%04d] r: %03d g: %03d b: %03d\n", i, j, bmp2.pixels[i * bmp1.dip.width + j].red, bmp2.pixels[i * bmp1.dip.width + j].green, bmp2.pixels[i * bmp1.dip.width + j].blue);
            //     printf("\tdiff [%04d][%04d] r: %03d g: %03d b: %03d\n", i, j, diff[i * bmp1.dip.width + j].red, diff[i * bmp1.dip.width + j].green, diff[i * bmp1.dip.width + j].blue);
            //     printf("\tsign [%04d][%04d] r: %03d g: %03d b: %03d\n", i, j, diffsign[i * bmp1.dip.width + j].channels.red, diffsign[i * bmp1.dip.width + j].channels.green, diffsign[i * bmp1.dip.width + j].channels.blue);
            //     printf("\n");
            // }

        }
    }


    free(diff);
    free(diffsign);
    free(bmp1.pixels);
    free(bmp2.pixels);
    return 0;

}