bmp.c

linux下开源图片codec

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#ifdef HAVE_ENDIAN_H
# include <endian.h>
#endif

#include "loader.h"

/* ---------------------------------------------------------------------- */

typedef unsigned int   uint32;
typedef unsigned short uint16;

/* bitmap files are little endian */
#if BYTE_ORDER == LITTLE_ENDIAN
# define le16_to_cpu(x) (x)
# define le32_to_cpu(x) (x)
#elif BYTE_ORDER == BIG_ENDIAN
# define le16_to_cpu(x) (((x>>8) & 0x00ff) |\
                         ((x<<8) & 0xff00))
# define le32_to_cpu(x) (((x>>24) & 0x000000ff) |\
                         ((x>>8)  & 0x0000ff00) |\
                         ((x<<8)  & 0x00ff0000) |\
                         ((x<<24) & 0xff000000))
#else
# error "Oops: unknown byte order"
#endif

/* ---------------------------------------------------------------------- */
/* load                                                                   */

struct bmp_hdr {
    uint32 foobar;

    uint32 size;              /* == BitMapInfoHeader */
    uint32 width;
    uint32 height;
    uint16 planes;
    uint16 bit_cnt;
    char   compression[4];
    uint32 image_size;
    uint32 xpels_meter;
    uint32 ypels_meter;
    uint32 num_colors;        /* used colors */
    uint32 imp_colors;        /* important colors */
    /* may be more for some codecs */
};

struct bmp_cmap {
    unsigned char blue;
    unsigned char green;
    unsigned char red;
    unsigned char unused;
};

struct bmp_state {
    struct bmp_hdr  hdr;
    struct bmp_cmap cmap[256];
    FILE *fp;
};

static void*
bmp_init(FILE *fp, char *filename, unsigned int page,
	 struct ida_image_info *i, int thumbnail)
{
    struct bmp_state *h;
    
    h = malloc(sizeof(*h));
    memset(h,0,sizeof(*h));
    h->fp = fp;

    fseek(fp,10,SEEK_SET);
    fread(&h->hdr,sizeof(struct bmp_hdr),1,fp);

#if BYTE_ORDER == BIG_ENDIAN
    h->hdr.foobar      = le32_to_cpu(h->hdr.foobar);
    h->hdr.size        = le32_to_cpu(h->hdr.size);
    h->hdr.width       = le32_to_cpu(h->hdr.width);
    h->hdr.height      = le32_to_cpu(h->hdr.height);
    
    h->hdr.planes      = le16_to_cpu(h->hdr.planes);
    h->hdr.bit_cnt     = le16_to_cpu(h->hdr.bit_cnt);
    
    h->hdr.image_size  = le32_to_cpu(h->hdr.image_size);
    h->hdr.xpels_meter = le32_to_cpu(h->hdr.xpels_meter);
    h->hdr.ypels_meter = le32_to_cpu(h->hdr.ypels_meter);
    h->hdr.num_colors  = le32_to_cpu(h->hdr.num_colors);
    h->hdr.imp_colors  = le32_to_cpu(h->hdr.imp_colors);
#endif

    if (debug)
	fprintf(stderr,"bmp: hdr=%d size=%dx%d planes=%d"
		" bits=%d size=%d res=%dx%d colors=%d/%d | %d\n",
		h->hdr.size,h->hdr.width,h->hdr.height,
		h->hdr.planes,h->hdr.bit_cnt,h->hdr.image_size,
		h->hdr.xpels_meter,h->hdr.ypels_meter,
		h->hdr.num_colors,h->hdr.imp_colors,h->hdr.foobar);
    if (h->hdr.bit_cnt != 1  &&
	h->hdr.bit_cnt != 4  &&
	h->hdr.bit_cnt != 8  &&
	h->hdr.bit_cnt != 24) {
	fprintf(stderr,"bmp: can't handle depth [%d]\n",h->hdr.bit_cnt);
	goto oops;
    }
    if (h->hdr.compression[0] || h->hdr.compression[1] ||
	h->hdr.compression[2] || h->hdr.compression[3]) {
	fprintf(stderr,"bmp: can't handle compressed bitmaps [%c%c%c%c]\n",
		h->hdr.compression[0],
		h->hdr.compression[1],
		h->hdr.compression[2],
		h->hdr.compression[3]);
	goto oops;
    }

    if (0 == h->hdr.num_colors && h->hdr.bit_cnt <= 8)
	h->hdr.num_colors = (1 << h->hdr.bit_cnt);
    if (h->hdr.num_colors > 256)
	h->hdr.num_colors = 256;
    if (h->hdr.num_colors) {
	fseek(fp,14+h->hdr.size,SEEK_SET);
	fread(&h->cmap,sizeof(struct bmp_cmap),h->hdr.num_colors,fp);
    }
    
    i->width  = h->hdr.width;
    i->height = h->hdr.height;
    if (h->hdr.xpels_meter)
	i->dpi = res_m_to_inch(h->hdr.xpels_meter);
    i->npages = 1;
    return h;

 oops:
    free(h);
    return NULL;
}

static void
bmp_read(unsigned char *dst, unsigned int line, void *data)
{
    struct bmp_state *h = data;
    unsigned int ll,y,x,pixel,byte = 0;
    
    ll = (((h->hdr.width * h->hdr.bit_cnt + 31) & ~0x1f) >> 3);
    y  = h->hdr.height - line - 1;
    fseek(h->fp,h->hdr.foobar + y * ll,SEEK_SET);

    switch (h->hdr.bit_cnt) {
    case 1:
	for (x = 0; x < h->hdr.width; x++) {
	    if (0 == (x & 0x07))
		byte = fgetc(h->fp);
	    pixel = byte & (0x80 >> (x & 0x07)) ? 1 : 0;
	    *(dst++) = h->cmap[pixel].red;
	    *(dst++) = h->cmap[pixel].green;
	    *(dst++) = h->cmap[pixel].blue;
	}
	break;
    case 4:
	for (x = 0; x < h->hdr.width; x++) {
	    if (x & 1) {
		pixel = byte & 0xf;
	    } else {
		byte = fgetc(h->fp);
		pixel = byte >> 4;
	    }
	    *(dst++) = h->cmap[pixel].red;
	    *(dst++) = h->cmap[pixel].green;
	    *(dst++) = h->cmap[pixel].blue;
	}
	break;
    case 8:
	for (x = 0; x < h->hdr.width; x++) {
	    pixel = fgetc(h->fp);
	    *(dst++) = h->cmap[pixel].red;
	    *(dst++) = h->cmap[pixel].green;
	    *(dst++) = h->cmap[pixel].blue;
	}
	break;
    case 24:
	for (x = 0; x < h->hdr.width; x++) {
	    dst[2] = fgetc(h->fp);
	    dst[1] = fgetc(h->fp);
	    dst[0] = fgetc(h->fp);
	    dst += 3;
	}
	break;
    default:
	memset(dst,128,h->hdr.width*3);
	break;
    }
}

static void
bmp_done(void *data)
{
    struct bmp_state *h = data;

    fclose(h->fp);
    free(h);
}

static struct ida_loader bmp_loader = {
    magic: "BM",
    moff:  0,
    mlen:  2,
    name:  "bmp",
    init:  bmp_init,
    read:  bmp_read,
    done:  bmp_done,
};

static void __init init_rd(void)
{
    load_register(&bmp_loader);
}