bmpgen

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

#define BYTES_PER_LINE(width) (3 * ((width) + 1) / 4) * 4

typedef unsigned char pix_t;
typedef unsigned int coord_t;

struct bmp_hdr {
    char bmp_propietary[2];
    int bmp_filesize;
    int bmp_reserved;
    int bmp_hdr_size;
    int bmp_info_size;
    int bmp_width;
    int bmp_height;
    short bmp_planes;
    short bmp_bits;
    int bmp_compression;
    int bmp_size_bytes;
    int bmp_x_res;
    int bmp_y_res;
    int bmp_colors;
    int bmp_imp_colors;
} __attribute__((__packed__));

struct bmp {
    struct bmp_hdr header;
    unsigned char *data;

    unsigned int height;
    unsigned int width;
    unsigned int bpl;

    char filename[128];
    FILE *handle;
};


struct bmp *bmp_new (const char *filename, int width, int height);
struct bmp *bmp_open (const char *filename);


void bmp_close (struct bmp *bmp);
int bmp_save (struct bmp *bmp);


void bmp_set_pixel (struct bmp *bmp, pix_t r, pix_t g, pix_t b,
            coord_t x, coord_t y);
void bmp_get_pixel (struct bmp *bmp, pix_t *r, pix_t *g, pix_t *b,
            coord_t x, coord_t y);

struct bmp *bmp_new (const char *filename, int width, int height)
{
    int bpl = BYTES_PER_LINE(width);
    struct bmp *bmp = malloc(sizeof(*bmp));

    bmp->height = height;
    bmp->width = width;

    bmp->data = malloc(bpl * (height + 1));

    bmp->bpl = bpl;

    bmp->header.bmp_propietary[0] = 'B';
    bmp->header.bmp_propietary[1] = 'M';
    bmp->header.bmp_hdr_size = 54;
    bmp->header.bmp_filesize = bmp->header.bmp_hdr_size + bpl * height;
    bmp->header.bmp_reserved = 0;
    bmp->header.bmp_info_size = 40;
    bmp->header.bmp_width = width;
    bmp->header.bmp_height = height;
    bmp->header.bmp_planes = 1;
    bmp->header.bmp_bits = 24;
    bmp->header.bmp_compression = 0;
    bmp->header.bmp_size_bytes = bpl * height;
    bmp->header.bmp_x_res = 2835;
    bmp->header.bmp_y_res = 2835;
    bmp->header.bmp_colors = 0;
    bmp->header.bmp_imp_colors = 0;

    strncpy(bmp->filename, filename, 128);

    bmp->handle = fopen(filename, "wb+");
    if (!bmp->handle) {
        perror("File open");
        free(bmp->data);
        free(bmp);
        return NULL;
    }

    fwrite(&bmp->header, sizeof(struct bmp_hdr), 1, bmp->handle);

    return bmp;
}

struct bmp *bmp_open (const char *filename)
{
    struct bmp *bmp = malloc(sizeof(*bmp));
    int x, y, ipos, pos;
    unsigned char *buffer;

    strncpy(bmp->filename, filename, 128);

    bmp->handle = fopen(filename, "r+b");
    if (!bmp->handle) {
        perror("File open");
        free(bmp);
        return NULL;
    }

    fread(&bmp->header, sizeof(struct bmp_hdr), 1, bmp->handle);

    bmp->height = bmp->header.bmp_height;
    bmp->width = bmp->header.bmp_width;

    bmp->bpl = BYTES_PER_LINE(bmp->width);
    bmp->data = malloc((bmp->bpl * bmp->height) + 1);

    if (!(buffer = malloc(bmp->bpl * bmp->height + 1))) {
        perror("Buffer allocation");
        return NULL;
    }

    fread(buffer, 1, (bmp->bpl * bmp->height), bmp->handle);

    pos = 0;

    for (y = 0; y < bmp->height; y++) {
        for (x = 0; x < bmp->width; x++) {
            ipos = 3 * ((bmp->height * y) + x);
            bmp->data[ipos + 0] = buffer[pos++];
            bmp->data[ipos + 1] = buffer[pos++];
            bmp->data[ipos + 2] = buffer[pos++];
        }
        pos += (-pos) & 3;
    }

    free(buffer);

    return bmp;
}

int bmp_save (struct bmp *bmp)
{
    int x, y, ipos, pos;
    unsigned char *buffer;

    if (!(buffer = malloc(bmp->bpl * bmp->height + 1))) {
        perror("Buffer allocation");
        return -1;
    }

    pos = 0;

    for (y = 0; y < bmp->height; y++) {
        for (x = 0; x < bmp->width; x++) {
            ipos = 3 * ((bmp->height * y) + x);
            buffer[pos++] = bmp->data[ipos + 0];
            buffer[pos++] = bmp->data[ipos + 1];
            buffer[pos++] = bmp->data[ipos + 2];
        }
        pos += (-pos) & 3;
    }

    fseek(bmp->handle, sizeof(struct bmp_hdr), SEEK_SET);
    fwrite(buffer, 1, pos, bmp->handle);

    free(buffer);

    return 0;
}


void bmp_close (struct bmp *bmp)
{
    fclose(bmp->handle);
    free(bmp->data);
    free(bmp);
}

void bmp_set_pixel (struct bmp *bmp, pix_t r, pix_t g, pix_t b,
            coord_t x, coord_t y)
{
    if (x > bmp->width)
        x = bmp->width;
    if (y > bmp->height)
        y = bmp->height;

    coord_t index = 3 * ((bmp->height * y) + x);

    bmp->data[index + 2] = r;
    bmp->data[index + 1] = g;
    bmp->data[index + 0] = b;
}

void bmp_get_pixel (struct bmp *bmp, pix_t *r, pix_t *g, pix_t *b,
            coord_t x, coord_t y)
{
    if (x > bmp->width)
        x = bmp->width;
    if (y > bmp->height)
        y = bmp->height;

    coord_t index = 3 * ((bmp->height * y) + x);

    (*r) = bmp->data[index + 2];
    (*g) = bmp->data[index + 1];
    (*b) = bmp->data[index + 0];
}

int main (int argc, const char * argv[])
{
    struct bmp *bmp = bmp_new("/file.bmp", 1024, 1024);
    int x, y;

    for (y = 0; y < bmp->height; y++) {
        for (x = 0; x < bmp->width; x++) {
            bmp_set_pixel(bmp, x & y, x ^ y, x | y, x, y);
        }
    }

    bmp_save (bmp);
    bmp_close(bmp);

    return 0;
}