IMG_lbm.c
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SDL_image: An example image loading library for use with SDL
Copyright (C) 1999, 2000, 2001 Sam Lantinga
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This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with this library; if not, write to the Free
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
Sam Lantinga
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slouken@libsdl.org
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/* $Id$ */
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/* This is a ILBM image file loading framework
Load IFF pictures, PBM & ILBM packing methods, with or without stencil
Written by Daniel Morais ( Daniel@Morais.com ) in September 2001
*/
#include <stdio.h>
#include <stdlib.h>
#include "SDL_endian.h"
#include "SDL_image.h"
#ifdef LOAD_LBM
#define MAXCOLORS 256
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/* Structure for an IFF picture ( BMHD = Bitmap Header ) */
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typedef struct
{
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Uint16 w, h; /* width & height of the bitmap in pixels */
Sint16 x, y; /* screen coordinates of the bitmap */
Uint8 planes; /* number of planes of the bitmap */
Uint8 mask; /* mask type ( 0 => no mask ) */
Uint8 tcomp; /* compression type */
Uint8 pad1; /* dummy value, for padding */
Uint16 tcolor; /* transparent color */
Uint8 xAspect, /* pixel aspect ratio */
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yAspect;
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Sint16 Lpage; /* width of the screen in pixels */
Sint16 Hpage; /* height of the screen in pixels */
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} BMHD;
int IMG_isLBM( SDL_RWops *src )
{
int is_LBM;
Uint8 magic[4+4+4];
is_LBM = 0;
if ( SDL_RWread( src, magic, 4+4+4, 1 ) )
{
if ( !memcmp( magic, "FORM", 4 ) &&
( !memcmp( magic + 8, "PBM ", 4 ) ||
!memcmp( magic + 8, "ILBM", 4 ) ) )
{
is_LBM = 1;
}
}
return( is_LBM );
}
SDL_Surface *IMG_LoadLBM_RW( SDL_RWops *src )
{
SDL_Surface *Image;
Uint8 id[4], pbm, colormap[MAXCOLORS*3], *MiniBuf, *ptr, count, color, msk;
Uint32 size, bytesloaded, nbcolors;
Uint32 i, j, bytesperline, nbplanes, plane, h;
Uint32 remainingbytes;
int width;
BMHD bmhd;
char *error;
Image = NULL;
error = NULL;
MiniBuf = NULL;
if ( src == NULL ) goto done;
if ( !SDL_RWread( src, id, 4, 1 ) )
{
error="error reading IFF chunk";
goto done;
}
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/* Should be the size of the file minus 4+4 ( 'FORM'+size ) */
if ( !SDL_RWread( src, &size, 4, 1 ) )
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{
error="error reading IFF chunk size";
goto done;
}
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/* As size is not used here, no need to swap it */
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if ( memcmp( id, "FORM", 4 ) != 0 )
{
error="not a IFF file";
goto done;
}
if ( !SDL_RWread( src, id, 4, 1 ) )
{
error="error reading IFF chunk";
goto done;
}
pbm = 0;
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/* File format : PBM=Packed Bitmap, ILBM=Interleaved Bitmap */
if ( !memcmp( id, "PBM ", 4 ) ) pbm = 1;
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else if ( memcmp( id, "ILBM", 4 ) )
{
error="not a IFF picture";
goto done;
}
nbcolors = 0;
memset( &bmhd, 0, sizeof( BMHD ) );
while ( memcmp( id, "BODY", 4 ) != 0 )
{
if ( !SDL_RWread( src, id, 4, 1 ) )
{
error="error reading IFF chunk";
goto done;
}
if ( !SDL_RWread( src, &size, 4, 1 ) )
{
error="error reading IFF chunk size";
goto done;
}
bytesloaded = 0;
size = SDL_SwapBE32( size );
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if ( !memcmp( id, "BMHD", 4 ) ) /* Bitmap header */
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{
if ( !SDL_RWread( src, &bmhd, sizeof( BMHD ), 1 ) )
{
error="error reading BMHD chunk";
goto done;
}
bytesloaded = sizeof( BMHD );
bmhd.w = SDL_SwapBE16( bmhd.w );
bmhd.h = SDL_SwapBE16( bmhd.h );
bmhd.x = SDL_SwapBE16( bmhd.x );
bmhd.y = SDL_SwapBE16( bmhd.y );
bmhd.tcolor = SDL_SwapBE16( bmhd.tcolor );
bmhd.Lpage = SDL_SwapBE16( bmhd.Lpage );
bmhd.Hpage = SDL_SwapBE16( bmhd.Hpage );
}
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if ( !memcmp( id, "CMAP", 4 ) ) /* palette ( Color Map ) */
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{
if ( !SDL_RWread( src, &colormap, size, 1 ) )
{
error="error reading CMAP chunk";
goto done;
}
bytesloaded = size;
nbcolors = size / 3;
}
if ( memcmp( id, "BODY", 4 ) )
{
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if ( size & 1 ) ++size; /* padding ! */
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size -= bytesloaded;
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/* skip the remaining bytes of this chunk */
if ( size ) SDL_RWseek( src, size, SEEK_CUR );
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}
}
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/* compute some usefull values, based on the bitmap header */
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width = ( bmhd.w + 15 ) & 0xFFFFFFF0; /* Width in pixels modulo 16 */
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bytesperline = ( ( bmhd.w + 15 ) / 16 ) * 2;
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nbplanes = bmhd.planes;
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if ( pbm ) /* File format : 'Packed Bitmap' */
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{
bytesperline *= 8;
nbplanes = 1;
}
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if ( bmhd.mask ) ++nbplanes; /* There is a mask ( 'stencil' ) */
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/* Allocate memory for a temporary buffer ( used for
decompression/deinterleaving ) */
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if ( ( MiniBuf = (void *)malloc( bytesperline * nbplanes ) ) == NULL )
{
error="no enough memory for temporary buffer";
goto done;
}
if ( ( Image = SDL_CreateRGBSurface( SDL_SWSURFACE, width, bmhd.h, 8, 0, 0, 0, 0 ) ) == NULL )
goto done;
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/* Update palette informations */
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Image->format->palette->ncolors = nbcolors;
ptr = &colormap[0];
for ( i=0; i<nbcolors; i++ )
{
Image->format->palette->colors[i].r = *ptr++;
Image->format->palette->colors[i].g = *ptr++;
Image->format->palette->colors[i].b = *ptr++;
}
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/* Get the bitmap */
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for ( h=0; h < bmhd.h; h++ )
{
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/* uncompress the datas of each planes */
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for ( plane=0; plane < nbplanes; plane++ )
{
ptr = MiniBuf + ( plane * bytesperline );
remainingbytes = bytesperline;
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if ( bmhd.tcomp == 1 ) /* Datas are compressed */
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{
do
{
if ( !SDL_RWread( src, &count, 1, 1 ) )
{
error="error reading BODY chunk";
goto done;
}
if ( count & 0x80 )
{
count ^= 0xFF;
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count += 2; /* now it */
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if ( !SDL_RWread( src, &color, 1, 1 ) )
{
error="error reading BODY chunk";
goto done;
}
memset( ptr, color, count );
}
else
{
++count;
if ( !SDL_RWread( src, ptr, count, 1 ) )
{
error="error reading BODY chunk";
goto done;
}
}
ptr += count;
remainingbytes -= count;
} while ( remainingbytes > 0 );
}
else
{
if ( !SDL_RWread( src, ptr, bytesperline, 1 ) )
{
error="error reading BODY chunk";
goto done;
}
}
}
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/* One line has been read, store it ! */
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ptr = Image->pixels;
ptr += h * width;
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if ( pbm ) /* File format : 'Packed Bitmap' */
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{
memcpy( ptr, MiniBuf, width );
}
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else /* We have to un-interlace the bits ! */
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{
size = ( width + 7 ) / 8;
for ( i=0; i < size; i++ )
{
memset( ptr, 0, 8 );
for ( plane=0; plane < nbplanes; plane++ )
{
color = *( MiniBuf + i + ( plane * bytesperline ) );
msk = 0x80;
for ( j=0; j<8; j++ )
{
if ( ( plane + j ) <= 7 ) ptr[j] |= (Uint8)( color & msk ) >> ( 7 - plane - j );
else ptr[j] |= (Uint8)( color & msk ) << ( plane + j - 7 );
msk >>= 1;
}
}
ptr += 8;
}
}
}
done:
if ( MiniBuf ) free( MiniBuf );
if ( error )
{
IMG_SetError( error );
SDL_FreeSurface( Image );
Image = NULL;
}
return( Image );
}
#else /* LOAD_LBM */
/* See if an image is contained in a data source */
int IMG_isLBM(SDL_RWops *src)
{
return(0);
}
/* Load an IFF type image from an SDL datasource */
SDL_Surface *IMG_LoadLBM_RW(SDL_RWops *src)
{
return(NULL);
}
#endif /* LOAD_LBM */