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#include <stdio.h>
#include <stdlib.h>
#include "meh.h"
unsigned short getshort(FILE *f){
unsigned short ret;
ret = getc(f);
ret = ret | (getc(f) << 8);
return ret;
}
unsigned long getlong(FILE *f){
unsigned short ret;
ret = getc(f);
ret = ret | (getc(f) << 8);
ret = ret | (getc(f) << 16);
ret = ret | (getc(f) << 24);
return ret;
}
struct rgb_t{
unsigned char r, g, b;
};
struct bmp_t{
struct image img;
unsigned long bitmapoffset;
int compression;
int bpp;
int ncolors;
struct rgb_t *colours;
unsigned int rowwidth;
};
struct image *bmp_open(FILE *f){
struct bmp_t *b;
unsigned long headersize;
rewind(f);
if(getc(f) != 'B' || getc(f) != 'M')
return NULL;
b = malloc(sizeof(struct bmp_t));
b->img.f = f;
fseek(f, 10, SEEK_SET);
b->bitmapoffset = getlong(f);
fseek(f, 14, SEEK_SET);
headersize = getlong(f);
if(headersize == 12){ /* OS/2 v1 */
b->ncolors = 0;
fseek(f, 18, SEEK_SET);
b->img.width = getshort(f);
b->img.height = getshort(f);
b->compression = 0;
}else{
fseek(f, 18, SEEK_SET);
b->img.width = getlong(f);
b->img.height = getlong(f);
fseek(f, 28, SEEK_SET);
b->bpp = getshort(f);
fseek(f, 30, SEEK_SET);
b->compression = getlong(f);
fseek(f, 46, SEEK_SET);
b->ncolors = getlong(f);
}
if(!b->ncolors){
b->ncolors = 1 << b->bpp;
}
if(b->compression){
fprintf(stderr, "unsupported compression method %i\n", b->compression);
return NULL;
}
if(b->bpp >= 16){
b->rowwidth = b->img.width * b->bpp;
}else{
int i;
b->colours = malloc(b->ncolors * sizeof(struct rgb_t));
fseek(f, 14+headersize, SEEK_SET);
for(i = 0; i < b->ncolors; i++){
b->colours[i].b = getc(f);
b->colours[i].g = getc(f);
b->colours[i].r = getc(f);
if(headersize != 12)
getc(f);
}
b->rowwidth = (b->img.width * b->bpp + 7) / 8;
}
if(b->rowwidth & 3){
b->rowwidth += 4 - (b->rowwidth & 3);
}
return (struct image *)b;
}
static void readrow(struct image *img, unsigned char *row, unsigned char *buf){
struct bmp_t *b = (struct bmp_t *)img;
int x;
int i = 0;
if(b->bpp == 24 || b->bpp == 32){
for(x = 0; x < img->width * 3; x+=3){
buf[x + 2] = row[i++];
buf[x + 1] = row[i++];
buf[x + 0] = row[i++];
if(b->bpp == 32)
i++;
}
}else if(b->bpp <= 8){
int mask;
int pixelsperbit = 8 / b->bpp;
mask = ~((~0) << b->bpp);
for(x = 0; x < img->width; x++){
unsigned char c = ((row[i / pixelsperbit]) >> ((8 - ((i+1) % pixelsperbit) * b->bpp)) % 8) & mask;
*buf++ = b->colours[c].r;
*buf++ = b->colours[c].g;
*buf++ = b->colours[c].b;
i++;
}
}else{
fprintf(stderr, "bad bpp %i\n", b->bpp);
return;
}
}
int bmp_read(struct image *img){
struct bmp_t *b = (struct bmp_t *)img;
FILE *f = img->f;
fseek(f, b->bitmapoffset, SEEK_SET);
int i, y;
int dy = img->width * 3;
i = img->height * dy;
unsigned char row[b->rowwidth];
for(y = img->height; y; y--){
i -= dy;
if(fread(row, 1, b->rowwidth, f) != b->rowwidth)
return 1;
readrow(img, row, &img->buf[i]);
}
return 0;
}
struct imageformat gif = {
bmp_open,
bmp_read
};
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