IMG_lbm.c
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SDL_image: An example image loading library for use with SDL
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Copyright (C) 1997-2006 Sam Lantinga
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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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
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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Sam Lantinga
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slouken@libsdl.org
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/* This is a ILBM image file loading framework
Load IFF pictures, PBM & ILBM packing methods, with or without stencil
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Written by Daniel Morais ( Daniel AT Morais DOT com ) in September 2001.
24 bits ILBM files support added by Marc Le Douarain (http://www.multimania.com/mavati)
in December 2002.
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EHB and HAM (specific Amiga graphic chip modes) support added by Marc Le Douarain
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(http://www.multimania.com/mavati) in December 2003.
Stencil and colorkey fixes by David Raulo (david.raulo AT free DOT fr) in February 2004.
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*/
#include <stdio.h>
#include <stdlib.h>
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#include <string.h>
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#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 )
{
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int is_LBM;
Uint8 magic[4+4+4];
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start = SDL_RWtell(src);
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is_LBM = 0;
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if ( SDL_RWread( src, magic, sizeof(magic), 1 ) )
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if ( !memcmp( magic, "FORM", 4 ) &&
( !memcmp( magic + 8, "PBM ", 4 ) ||
!memcmp( magic + 8, "ILBM", 4 ) ) )
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{
is_LBM = 1;
}
}
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SDL_RWseek(src, start, SEEK_SET);
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return( is_LBM );
}
SDL_Surface *IMG_LoadLBM_RW( SDL_RWops *src )
{
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SDL_Surface *Image;
Uint8 id[4], pbm, colormap[MAXCOLORS*3], *MiniBuf, *ptr, count, color, msk;
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Uint32 size, bytesloaded, nbcolors;
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Uint32 i, j, bytesperline, nbplanes, plane, h;
Uint32 remainingbytes;
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Uint32 width;
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BMHD bmhd;
char *error;
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Uint8 flagHAM,flagEHB;
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Image = NULL;
error = NULL;
MiniBuf = NULL;
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if ( !src ) {
/* The error message has been set in SDL_RWFromFile */
return NULL;
}
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start = SDL_RWtell(src);
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if ( !SDL_RWread( src, id, 4, 1 ) )
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error="error reading IFF chunk";
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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";
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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 )
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error="not a IFF file";
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goto done;
}
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if ( !SDL_RWread( src, id, 4, 1 ) )
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error="error reading IFF chunk";
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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 ) )
{
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error="not a IFF picture";
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goto done;
}
nbcolors = 0;
memset( &bmhd, 0, sizeof( BMHD ) );
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flagHAM = 0;
flagEHB = 0;
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while ( memcmp( id, "BODY", 4 ) != 0 )
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{
if ( !SDL_RWread( src, id, 4, 1 ) )
{
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error="error reading IFF chunk";
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goto done;
}
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if ( !SDL_RWread( src, &size, 4, 1 ) )
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error="error reading IFF chunk size";
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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 ) )
{
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error="error reading BMHD chunk";
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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 ) )
{
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error="error reading CMAP chunk";
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goto done;
}
bytesloaded = size;
nbcolors = size / 3;
}
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if ( !memcmp( id, "CAMG", 4 ) ) /* Amiga ViewMode */
{
Uint32 viewmodes;
if ( !SDL_RWread( src, &viewmodes, sizeof(viewmodes), 1 ) )
{
error="error reading CAMG chunk";
goto done;
}
bytesloaded = size;
viewmodes = SDL_SwapBE32( viewmodes );
if ( viewmodes & 0x0800 )
flagHAM = 1;
if ( viewmodes & 0x0080 )
flagEHB = 1;
}
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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;
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nbplanes = 1;
}
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if ( bmhd.mask & 1 ) ++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 )
{
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error="no enough memory for temporary buffer";
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goto done;
}
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if ( ( Image = SDL_CreateRGBSurface( SDL_SWSURFACE, width, bmhd.h, (bmhd.planes==24 || flagHAM==1)?24:8, 0, 0, 0, 0 ) ) == NULL )
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goto done;
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if ( bmhd.mask & 2 ) /* There is a transparent color */
SDL_SetColorKey( Image, SDL_SRCCOLORKEY, bmhd.tcolor );
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/* Update palette informations */
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/* There is no palette in 24 bits ILBM file */
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if ( nbcolors>0 && flagHAM==0 )
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int nbrcolorsfinal = 1 << nbplanes;
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ptr = &colormap[0];
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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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/* Amiga EHB mode (Extra-Half-Bright) */
/* 6 bitplanes mode with a 32 colors palette */
/* The 32 last colors are the same but divided by 2 */
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/* Some Amiga pictures save 64 colors with 32 last wrong colors, */
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/* they shouldn't !, and here we overwrite these 32 bad colors. */
if ( (nbcolors==32 || flagEHB ) && (1<<bmhd.planes)==64 )
{
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nbcolors = 64;
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ptr = &colormap[0];
for ( i=32; i<64; i++ )
{
Image->format->palette->colors[i].r = (*ptr++)/2;
Image->format->palette->colors[i].g = (*ptr++)/2;
Image->format->palette->colors[i].b = (*ptr++)/2;
}
}
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/* If nbcolors < 2^nbplanes, repeat the colormap */
/* This happens when pictures have a stencil mask */
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if ( nbrcolorsfinal > (1<<bmhd.planes) ) {
nbrcolorsfinal = (1<<bmhd.planes);
}
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for ( i=nbcolors; i < (Uint32)nbrcolorsfinal; i++ )
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{
Image->format->palette->colors[i].r = Image->format->palette->colors[i%nbcolors].r;
Image->format->palette->colors[i].g = Image->format->palette->colors[i%nbcolors].g;
Image->format->palette->colors[i].b = Image->format->palette->colors[i%nbcolors].b;
}
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Image->format->palette->ncolors = nbrcolorsfinal;
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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 */
for ( plane=0; plane < nbplanes; plane++ )
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ptr = MiniBuf + ( plane * bytesperline );
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remainingbytes = bytesperline;
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if ( bmhd.tcomp == 1 ) /* Datas are compressed */
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if ( !SDL_RWread( src, &count, 1, 1 ) )
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error="error reading BODY chunk";
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goto done;
}
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if ( count & 0x80 )
{
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count ^= 0xFF;
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
{
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if ( !SDL_RWread( src, ptr, count, 1 ) )
{
error="error reading BODY chunk";
goto done;
}
}
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ptr += count;
remainingbytes -= count;
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} while ( remainingbytes > 0 );
}
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if ( !SDL_RWread( src, ptr, bytesperline, 1 ) )
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error="error reading BODY chunk";
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goto done;
}
}
}
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/* One line has been read, store it ! */
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ptr = Image->pixels;
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if ( nbplanes==24 || flagHAM==1 )
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ptr += h * width * 3;
else
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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if ( nbplanes!=24 && flagHAM==0 )
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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;
}
}
else
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Uint32 finalcolor = 0;
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size = ( width + 7 ) / 8;
/* 24 bitplanes ILBM : R0...R7,G0...G7,B0...B7 */
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/* or HAM (6 bitplanes) or HAM8 (8 bitplanes) modes */
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for ( i=0; i<width; i=i+8 )
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Uint8 maskBit = 0x80;
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for ( j=0; j<8; j++ )
{
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Uint32 pixelcolor = 0;
Uint32 maskColor = 1;
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Uint8 dataBody;
for ( plane=0; plane < nbplanes; plane++ )
{
dataBody = MiniBuf[ plane*size+i/8 ];
if ( dataBody&maskBit )
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pixelcolor = pixelcolor | maskColor;
maskColor = maskColor<<1;
}
/* HAM : 12 bits RGB image (4 bits per color component) */
/* HAM8 : 18 bits RGB image (6 bits per color component) */
if ( flagHAM )
{
switch( pixelcolor>>(nbplanes-2) )
{
case 0: /* take direct color from palette */
finalcolor = colormap[ pixelcolor*3 ] + (colormap[ pixelcolor*3+1 ]<<8) + (colormap[ pixelcolor*3+2 ]<<16);
break;
case 1: /* modify only blue component */
finalcolor = finalcolor&0x00FFFF;
finalcolor = finalcolor | (pixelcolor<<(16+(10-nbplanes)));
break;
case 2: /* modify only red component */
finalcolor = finalcolor&0xFFFF00;
finalcolor = finalcolor | pixelcolor<<(10-nbplanes);
break;
case 3: /* modify only green component */
finalcolor = finalcolor&0xFF00FF;
finalcolor = finalcolor | (pixelcolor<<(8+(10-nbplanes)));
break;
}
}
else
{
finalcolor = pixelcolor;
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}
if ( SDL_BYTEORDER == SDL_LIL_ENDIAN )
{
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*ptr++ = finalcolor>>16;
*ptr++ = finalcolor>>8;
*ptr++ = finalcolor;
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}
else
{
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*ptr++ = finalcolor;
*ptr++ = finalcolor>>8;
*ptr++ = finalcolor>>16;
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}
maskBit = maskBit>>1;
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}
}
}
}
}
done:
if ( MiniBuf ) free( MiniBuf );
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if ( error )
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SDL_RWseek(src, start, SEEK_SET);
if ( Image ) {
SDL_FreeSurface( Image );
Image = NULL;
}
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IMG_SetError( error );
}
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 */