IMG_pnm.c
author Ryan C. Gordon <icculus@icculus.org>
Tue, 13 Feb 2007 10:09:17 +0000
changeset 154 201cc5c1b373
parent 121 1bf9c0c87374
child 186 5fbbeabf647f
permissions -rw-r--r--
SDL_image shouldn't dereference a rwops if it's NULL.

Fixes Bugzilla #284.
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/*
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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,
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    but WITHOUT ANY WARRANTY; without even the implied warranty of
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    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
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    License along with this library; if not, write to the Free Software
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    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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*/
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/*
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 * PNM (portable anymap) image loader:
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 *
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 * Supports: PBM, PGM and PPM, ASCII and binary formats
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 * (PBM and PGM are loaded as 8bpp surfaces)
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 * Does not support: maximum component value > 255
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 */
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#include <stdio.h>
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#include <stdlib.h>
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#include <ctype.h>
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#include <string.h>
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#include "SDL_image.h"
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#ifdef LOAD_PNM
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/* See if an image is contained in a data source */
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int IMG_isPNM(SDL_RWops *src)
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{
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	int start;
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	int is_PNM;
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	char magic[2];
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	if ( !src )
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		return 0;
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	start = SDL_RWtell(src);
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	is_PNM = 0;
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	if ( SDL_RWread(src, magic, sizeof(magic), 1) ) {
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		/*
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		 * PNM magic signatures:
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		 * P1	PBM, ascii format
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		 * P2	PGM, ascii format
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		 * P3	PPM, ascii format
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		 * P4	PBM, binary format
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		 * P5	PGM, binary format
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		 * P6	PPM, binary format
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		 * P7	PAM, a general wrapper for PNM data
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		 */
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		if ( magic[0] == 'P' && magic[1] >= '1' && magic[1] <= '6' ) {
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			is_PNM = 1;
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		}
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	}
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	SDL_RWseek(src, start, SEEK_SET);
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	return(is_PNM);
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}
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/* read a non-negative integer from the source. return -1 upon error */
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static int ReadNumber(SDL_RWops *src)
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{
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	int number;
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	unsigned char ch;
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	/* Initialize return value */
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	number = 0;
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	/* Skip leading whitespace */
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	do {
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		if ( ! SDL_RWread(src, &ch, 1, 1) ) {
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			return(0);
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		}
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		/* Eat comments as whitespace */
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		if ( ch == '#' ) {  /* Comment is '#' to end of line */
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			do {
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				if ( ! SDL_RWread(src, &ch, 1, 1) ) {
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					return -1;
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				}
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			} while ( (ch != '\r') && (ch != '\n') );
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		}
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	} while ( isspace(ch) );
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	/* Add up the number */
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	do {
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		number *= 10;
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		number += ch-'0';
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		if ( !SDL_RWread(src, &ch, 1, 1) ) {
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			return -1;
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		}
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	} while ( isdigit(ch) );
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	return(number);
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}
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SDL_Surface *IMG_LoadPNM_RW(SDL_RWops *src)
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{
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	int start;
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	SDL_Surface *surface = NULL;
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	int width, height;
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	int maxval, y, bpl;
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	Uint8 *row;
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	Uint8 *buf = NULL;
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	char *error = NULL;
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	Uint8 magic[2];
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	int ascii;
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	enum { PBM, PGM, PPM, PAM } kind;
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#define ERROR(s) do { error = (s); goto done; } while(0)
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	if ( !src ) {
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		/* The error message has been set in SDL_RWFromFile */
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		return NULL;
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	}
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	start = SDL_RWtell(src);
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	SDL_RWread(src, magic, 2, 1);
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	kind = magic[1] - '1';
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	ascii = 1;
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	if(kind >= 3) {
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		ascii = 0;
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		kind -= 3;
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	}
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	width = ReadNumber(src);
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	height = ReadNumber(src);
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	if(width <= 0 || height <= 0)
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		ERROR("Unable to read image width and height");
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	if(kind != PBM) {
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		maxval = ReadNumber(src);
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		if(maxval <= 0 || maxval > 255)
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			ERROR("unsupported PNM format");
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	} else
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		maxval = 255;	/* never scale PBMs */
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	/* binary PNM allows just a single character of whitespace after
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	   the last parameter, and we've already consumed it */
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	if(kind == PPM) {
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		/* 24-bit surface in R,G,B byte order */
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		surface = SDL_AllocSurface(SDL_SWSURFACE, width, height, 24,
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#if SDL_BYTEORDER == SDL_LIL_ENDIAN
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					   0x000000ff, 0x0000ff00, 0x00ff0000,
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#else
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					   0x00ff0000, 0x0000ff00, 0x000000ff,
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#endif
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					   0);
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	} else {
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		/* load PBM/PGM as 8-bit indexed images */
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		surface = SDL_AllocSurface(SDL_SWSURFACE, width, height, 8,
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					   0, 0, 0, 0);
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	}
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	if ( surface == NULL )
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		ERROR("Out of memory");
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	bpl = width * surface->format->BytesPerPixel;
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	if(kind == PGM) {
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		SDL_Color *c = surface->format->palette->colors;
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		int i;
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		for(i = 0; i < 256; i++)
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			c[i].r = c[i].g = c[i].b = i;
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		surface->format->palette->ncolors = 256;
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	} else if(kind == PBM) {
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		/* for some reason PBM has 1=black, 0=white */
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		SDL_Color *c = surface->format->palette->colors;
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		c[0].r = c[0].g = c[0].b = 255;
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		c[1].r = c[1].g = c[1].b = 0;
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		surface->format->palette->ncolors = 2;
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		bpl = (width + 7) >> 3;
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		buf = malloc(bpl);
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		if(buf == NULL)
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			ERROR("Out of memory");
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	}
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	/* Read the image into the surface */
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	row = surface->pixels;
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	for(y = 0; y < height; y++) {
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		if(ascii) {
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			int i;
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			if(kind == PBM) {
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				for(i = 0; i < width; i++) {
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					Uint8 ch;
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					do {
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						if(!SDL_RWread(src, &ch,
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							       1, 1))
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						       ERROR("file truncated");
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						ch -= '0';
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					} while(ch > 1);
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					row[i] = ch;
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				}
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			} else {
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				for(i = 0; i < bpl; i++) {
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					int c;
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					c = ReadNumber(src);
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					if(c < 0)
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						ERROR("file truncated");
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					row[i] = c;
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				}
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			}
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		} else {
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			Uint8 *dst = (kind == PBM) ? buf : row;
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			if(!SDL_RWread(src, dst, bpl, 1))
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				ERROR("file truncated");
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			if(kind == PBM) {
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				/* expand bitmap to 8bpp */
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				int i;
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				for(i = 0; i < width; i++) {
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					int bit = 7 - (i & 7);
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					row[i] = (buf[i >> 3] >> bit) & 1;
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				}
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			}
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		}
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		if(maxval < 255) {
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			/* scale up to full dynamic range (slow) */
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			int i;
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			for(i = 0; i < bpl; i++)
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				row[i] = row[i] * 255 / maxval;
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		}
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		row += surface->pitch;
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	}
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done:
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	free(buf);
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	if(error) {
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		SDL_RWseek(src, start, SEEK_SET);
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		if ( surface ) {
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			SDL_FreeSurface(surface);
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			surface = NULL;
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		}
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		IMG_SetError(error);
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	}
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	return(surface);
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}
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#else
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/* See if an image is contained in a data source */
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int IMG_isPNM(SDL_RWops *src)
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{
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	return(0);
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}
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/* Load a PNM type image from an SDL datasource */
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SDL_Surface *IMG_LoadPNM_RW(SDL_RWops *src)
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{
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	return(NULL);
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}
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#endif /* LOAD_PNM */