www.pudn.com > ilib > IBMP.c
/*
* IBMP.c
*
* Image library
*
* Description:
* Read BMP files.
*
* History:
* 01-Apr-00 Jim Winstead jimw@trainedmonkey.com
* Created
*
****************************************************************************/
#include
#include
#include
#include
#include
#include "Ilib.h"
#include "IlibP.h"
#define BMP_HEADER ('B' + ('M' << 8))
/* Compression formats */
#define BI_RGB 0
#define BI_RLE8 1
#define BI_RLE4 2
#define BI_BITFIELDS 3
#define SET_PIXEL(buffer, byte) \
do { \
*(buffer+0) = (colortable[byte&0xff]&(0xff<<16))>>16; \
*(buffer+1) = (colortable[byte&0xff]&(0xff<<8))>>8; \
*(buffer+2) = (colortable[byte&0xff]&(0xff<<0))>>0; \
} while (0);
static int ReadShort (fp, ret)
FILE *fp;
int *ret;
{
int c = fgetc(fp);
if (c == EOF) return 0;
*ret = (c&0xff);
c = fgetc(fp);
if (c == EOF) return 0;
*ret |= (c&0xff) << 8;
return 1;
}
static int ReadLong (fp, ret)
FILE *fp;
int *ret;
{
int c = fgetc(fp);
if (c == EOF) return 0;
*ret = (c&0xff);
c = fgetc(fp);
if (c == EOF) return 0;
*ret |= (c&0xff) << 8;
c = fgetc(fp);
if (c == EOF) return 0;
*ret |= (c&0xff) << 16;
c = fgetc(fp);
if (c == EOF) return 0;
*ret |= (c&0xff) << 24;
return 1;
}
IError _IReadBMP ( fp, options, image_return )
FILE *fp;
IOptions options;
IImageP **image_return;
{
IImageP *image = NULL;
int scratch, fileSize, offset, w, h, depth, compression,
imagesize, xpelspermeter, ypelspermeter, colorsused, colorsimportant;
int redmask, greenmask, bluemask,
redshift, greenshift, blueshift,
redbits, greenbits, bluebits;
int *colortable = NULL;
/* read the header and make sure this is a BMP file */
if (!ReadShort(fp, &scratch) || scratch != BMP_HEADER) return IInvalidFormat;
/* read the file size (not sure this is useful) */
if (!ReadLong(fp, &fileSize)) return (IInvalidFormat);
/* read the two reserved fields (must be zero, according to spec) */
if (!ReadShort(fp, &scratch) || scratch != 0) return (IInvalidFormat);
if (!ReadShort(fp, &scratch) || scratch != 0) return (IInvalidFormat);
/* read the offset of the actual graphic bits */
if (!ReadLong(fp, &offset)) return (IInvalidFormat);
/*fprintf(stderr, "offset = %d\n", offset);*/
/* verify that the header is 40 bytes */
/* XXX: really should save this and just skip bytes we don't understand. */
/* and we could be using this to detect things in OS/2 format */
if (!ReadLong(fp, &scratch) || scratch != 40) return (IInvalidFormat);
/* get image size and depth */
if (!ReadLong(fp, &w)) return (IInvalidFormat);
if (!ReadLong(fp, &h)) return (IInvalidFormat);
if (!ReadShort(fp, &scratch) || scratch != 1) return (IInvalidFormat);
if (!ReadShort(fp, &depth)) return (IInvalidFormat);
/*fprintf(stderr, "image size: %dx%dx%d\n", w, h, depth);*/
if (!ReadLong(fp, &compression)) return (IInvalidFormat);
if (!ReadLong(fp, &imagesize)) return (IInvalidFormat);
if (!ReadLong(fp, &xpelspermeter)) return (IInvalidFormat);
if (!ReadLong(fp, &ypelspermeter)) return (IInvalidFormat);
if (!ReadLong(fp, &colorsused)) return (IInvalidFormat);
if (!ReadLong(fp, &colorsimportant)) return (IInvalidFormat);
/* we have read 40 bytes of header */
/* we have read 54 bytes of data from the file */
/*
fprintf(stderr, "compression=%d, imagesize=%d, colorsused=%d\n",
compression,
imagesize,
colorsused);
*/
/* get the masks, shifts, and bits for bitfields (16 and 32 bits) */
if (compression == BI_BITFIELDS) {
if (!ReadLong(fp,&redmask)) return IInvalidImage;
for (redshift = 0; !(redmask&(1<= 0; y--) {
for (x = 0; x < w; x++) {
int r,g,b;
r = fgetc(fp); g = fgetc(fp); b = fgetc(fp);
/* this leaks the image object if we hit a premature EOF */
if (r == EOF || g == EOF || b == EOF) return (IInvalidFormat);
*(image->data + (y*3*w) + (x*3)) = b;
*(image->data + (y*3*w) + (x*3) + 1) = g;
*(image->data + (y*3*w) + (x*3) + 2) = r;
}
}
}
else if (depth == 16 && compression == BI_BITFIELDS) {
int x, y;
/* slurp in the data */
for (y = h - 1; y >= 0; y--) {
for (x = 0; x < w; x++) {
char *pixel = image->data + (y*3*w) + (x*3);
int color;
/* this leaks the image object if we hit a premature EOF */
if (!ReadShort(fp, &color)) return (IInvalidFormat);
/* scale 5/6 bit values to 8 bits */
*(pixel + 0) = (((color&redmask)>>redshift)<<8)>>redbits;
*(pixel + 1) = (((color&greenmask)>>greenshift)<<8)>>greenbits;
*(pixel + 2) = (((color&bluemask)>>blueshift)<<8)>>bluebits;
}
}
}
else if (depth == 8 && compression == BI_RGB) {
int x, y;
/*fprintf(stderr, "8 bit, no compression\n");*/
for (y = h - 1; y >= 0; y--) {
for (x = 0; x < w; x++) {
char *pixel = image->data+(y*w*3)+(x*3);
int byte = fgetc(fp); if (byte == EOF) return IInvalidFormat;
SET_PIXEL(pixel, byte);
}
}
} else if (depth <= 8 && compression) {
int byte, count, x, y;
char *buffer = image->data+w*(h-1)*3;
for (y = 0; y < h; ) {
count = fgetc(fp);
if (count == EOF) return (IInvalidFormat);
if (count != 0) {
/*fprintf(stderr, "stretch of %d bytes\n", count);*/
byte = fgetc(fp); if (byte == EOF) return (IInvalidFormat);
for (scratch = 0; scratch < count; scratch++) {
if (compression == 1) {
SET_PIXEL(buffer, byte);
}
else {
int thisbyte = (scratch & 0x01) ? (byte & 0x0f) : ((byte >> 4) & 0x0f);
SET_PIXEL(buffer, thisbyte);
}
buffer += 3;
}
}
else {
count = fgetc(fp);
if (count == EOF) return (IInvalidFormat);
if (count == 0x01) break; /* end of bitmap */
switch (count) {
case 0x00: /* end of the line */
/*fprintf(stderr, "hit end of line %d\n", y);*/
y++;
buffer = image->data+w*(h-y-1)*3;
break;
case 0x02: /* goto specific position */
x = fgetc(fp);
y = fgetc(fp);
/*fprintf(stderr, "going to %d,%d\n", x, y);*/
if (x == EOF || y == EOF) return (IInvalidFormat);
buffer = image->data+w*(h-y-1)*3+(x*3);
break;
default: /* a bunch of literal bytes */
/*fprintf(stderr, "handling %d literal bytes\n", count);*/
for (scratch = 0; scratch < count; scratch++) {
byte = fgetc(fp); if (byte == EOF) return (IInvalidFormat);
if (compression == 1) {
SET_PIXEL(buffer, byte);
}
else {
int thisbyte = (scratch & 0x01) ? (byte & 0x0f) : ((byte >> 4) & 0x0f);
SET_PIXEL(buffer, thisbyte);
}
buffer += 3;
}
/* handle padding */
if (compression == 1) {
if (count & 0x01) {
/*fprintf(stderr, "eating padding\n");*/
(void)fgetc(fp);
}
}
else if ((count & 0x03) == 1 || ((count & 0x03) == 2)) {
(void)fgetc(fp);
}
break;
}
}
}
}
else {
_IFreeImage(image);
return (IInvalidFormat);
}
if (colortable) free(colortable);
*image_return = image;
return ( INoError );
}