IMG_pnm.c
author Sam Lantinga <slouken@libsdl.org>
Sat, 04 Feb 2006 23:26:45 +0000
changeset 119 336c49447e0d
parent 118 c5e736a47ad2
child 121 1bf9c0c87374
permissions -rw-r--r--
Added support for XV thumbnail images
     1 /*
     2     SDL_image:  An example image loading library for use with SDL
     3     Copyright (C) 1999-2004 Sam Lantinga
     4 
     5     This library is free software; you can redistribute it and/or
     6     modify it under the terms of the GNU Library General Public
     7     License as published by the Free Software Foundation; either
     8     version 2 of the License, or (at your option) any later version.
     9 
    10     This library is distributed in the hope that it will be useful,
    11     but WITHOUT ANY WARRANTY; without even the implied warranty of
    12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    13     Library General Public License for more details.
    14 
    15     You should have received a copy of the GNU Library General Public
    16     License along with this library; if not, write to the Free
    17     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    18 
    19     Sam Lantinga
    20     slouken@libsdl.org
    21 */
    22 
    23 /* $Id$ */
    24 
    25 /*
    26  * PNM (portable anymap) image loader:
    27  *
    28  * Supports: PBM, PGM and PPM, ASCII and binary formats
    29  * (PBM and PGM are loaded as 8bpp surfaces)
    30  * Does not support: maximum component value > 255
    31  */
    32 
    33 #include <stdio.h>
    34 #include <stdlib.h>
    35 #include <ctype.h>
    36 #include <string.h>
    37 
    38 #include "SDL_image.h"
    39 
    40 #ifdef LOAD_PNM
    41 
    42 /* See if an image is contained in a data source */
    43 int IMG_isPNM(SDL_RWops *src)
    44 {
    45 	int start;
    46 	int is_PNM;
    47 	char magic[2];
    48 
    49 	start = SDL_RWtell(src);
    50 	is_PNM = 0;
    51 	if ( SDL_RWread(src, magic, sizeof(magic), 1) ) {
    52 		/*
    53 		 * PNM magic signatures:
    54 		 * P1	PBM, ascii format
    55 		 * P2	PGM, ascii format
    56 		 * P3	PPM, ascii format
    57 		 * P4	PBM, binary format
    58 		 * P5	PGM, binary format
    59 		 * P6	PPM, binary format
    60 		 * P7	PAM, a general wrapper for PNM data
    61 		 */
    62 		if ( magic[0] == 'P' && magic[1] >= '1' && magic[1] <= '6' ) {
    63 			is_PNM = 1;
    64 		}
    65 	}
    66 	SDL_RWseek(src, start, SEEK_SET);
    67 	return(is_PNM);
    68 }
    69 
    70 /* read a non-negative integer from the source. return -1 upon error */
    71 static int ReadNumber(SDL_RWops *src)
    72 {
    73 	int number;
    74 	unsigned char ch;
    75 
    76 	/* Initialize return value */
    77 	number = 0;
    78 
    79 	/* Skip leading whitespace */
    80 	do {
    81 		if ( ! SDL_RWread(src, &ch, 1, 1) ) {
    82 			return(0);
    83 		}
    84 		/* Eat comments as whitespace */
    85 		if ( ch == '#' ) {  /* Comment is '#' to end of line */
    86 			do {
    87 				if ( ! SDL_RWread(src, &ch, 1, 1) ) {
    88 					return -1;
    89 				}
    90 			} while ( (ch != '\r') && (ch != '\n') );
    91 		}
    92 	} while ( isspace(ch) );
    93 
    94 	/* Add up the number */
    95 	do {
    96 		number *= 10;
    97 		number += ch-'0';
    98 
    99 		if ( !SDL_RWread(src, &ch, 1, 1) ) {
   100 			return -1;
   101 		}
   102 	} while ( isdigit(ch) );
   103 
   104 	return(number);
   105 }
   106 
   107 SDL_Surface *IMG_LoadPNM_RW(SDL_RWops *src)
   108 {
   109 	int start;
   110 	SDL_Surface *surface = NULL;
   111 	int width, height;
   112 	int maxval, y, bpl;
   113 	Uint8 *row;
   114 	Uint8 *buf = NULL;
   115 	char *error = NULL;
   116 	Uint8 magic[2];
   117 	int ascii;
   118 	enum { PBM, PGM, PPM, PAM } kind;
   119 
   120 #define ERROR(s) do { error = (s); goto done; } while(0)
   121 
   122 	if ( !src ) {
   123 		/* The error message has been set in SDL_RWFromFile */
   124 		return NULL;
   125 	}
   126 	start = SDL_RWtell(src);
   127 
   128 	SDL_RWread(src, magic, 2, 1);
   129 	kind = magic[1] - '1';
   130 	ascii = 1;
   131 	if(kind >= 3) {
   132 		ascii = 0;
   133 		kind -= 3;
   134 	}
   135 
   136 	width = ReadNumber(src);
   137 	height = ReadNumber(src);
   138 	if(width <= 0 || height <= 0)
   139 		ERROR("Unable to read image width and height");
   140 
   141 	if(kind != PBM) {
   142 		maxval = ReadNumber(src);
   143 		if(maxval <= 0 || maxval > 255)
   144 			ERROR("unsupported PNM format");
   145 	} else
   146 		maxval = 255;	/* never scale PBMs */
   147 
   148 	/* binary PNM allows just a single character of whitespace after
   149 	   the last parameter, and we've already consumed it */
   150 
   151 	if(kind == PPM) {
   152 		/* 24-bit surface in R,G,B byte order */
   153 		surface = SDL_AllocSurface(SDL_SWSURFACE, width, height, 24,
   154 #if SDL_BYTEORDER == SDL_LIL_ENDIAN
   155 					   0x000000ff, 0x0000ff00, 0x00ff0000,
   156 #else
   157 					   0x00ff0000, 0x0000ff00, 0x000000ff,
   158 #endif
   159 					   0);
   160 	} else {
   161 		/* load PBM/PGM as 8-bit indexed images */
   162 		surface = SDL_AllocSurface(SDL_SWSURFACE, width, height, 8,
   163 					   0, 0, 0, 0);
   164 	}
   165 	if ( surface == NULL )
   166 		ERROR("Out of memory");
   167 	bpl = width * surface->format->BytesPerPixel;
   168 	if(kind == PGM) {
   169 		SDL_Color *c = surface->format->palette->colors;
   170 		int i;
   171 		for(i = 0; i < 256; i++)
   172 			c[i].r = c[i].g = c[i].b = i;
   173 		surface->format->palette->ncolors = 256;
   174 	} else if(kind == PBM) {
   175 		/* for some reason PBM has 1=black, 0=white */
   176 		SDL_Color *c = surface->format->palette->colors;
   177 		c[0].r = c[0].g = c[0].b = 255;
   178 		c[1].r = c[1].g = c[1].b = 0;
   179 		surface->format->palette->ncolors = 2;
   180 		bpl = (width + 7) >> 3;
   181 		buf = malloc(bpl);
   182 		if(buf == NULL)
   183 			ERROR("Out of memory");
   184 	}
   185 
   186 	/* Read the image into the surface */
   187 	row = surface->pixels;
   188 	for(y = 0; y < height; y++) {
   189 		if(ascii) {
   190 			int i;
   191 			if(kind == PBM) {
   192 				for(i = 0; i < width; i++) {
   193 					Uint8 ch;
   194 					do {
   195 						if(!SDL_RWread(src, &ch,
   196 							       1, 1))
   197 						       ERROR("file truncated");
   198 						ch -= '0';
   199 					} while(ch > 1);
   200 					row[i] = ch;
   201 				}
   202 			} else {
   203 				for(i = 0; i < bpl; i++) {
   204 					int c;
   205 					c = ReadNumber(src);
   206 					if(c < 0)
   207 						ERROR("file truncated");
   208 					row[i] = c;
   209 				}
   210 			}
   211 		} else {
   212 			Uint8 *dst = (kind == PBM) ? buf : row;
   213 			if(!SDL_RWread(src, dst, bpl, 1))
   214 				ERROR("file truncated");
   215 			if(kind == PBM) {
   216 				/* expand bitmap to 8bpp */
   217 				int i;
   218 				for(i = 0; i < width; i++) {
   219 					int bit = 7 - (i & 7);
   220 					row[i] = (buf[i >> 3] >> bit) & 1;
   221 				}
   222 			}
   223 		}
   224 		if(maxval < 255) {
   225 			/* scale up to full dynamic range (slow) */
   226 			int i;
   227 			for(i = 0; i < bpl; i++)
   228 				row[i] = row[i] * 255 / maxval;
   229 		}
   230 		row += surface->pitch;
   231 	}
   232 done:
   233 	free(buf);
   234 	if(error) {
   235 		SDL_RWseek(src, start, SEEK_SET);
   236 		if ( surface ) {
   237 			SDL_FreeSurface(surface);
   238 			surface = NULL;
   239 		}
   240 		IMG_SetError(error);
   241 	}
   242 	return(surface);
   243 }
   244 
   245 #else
   246 
   247 /* See if an image is contained in a data source */
   248 int IMG_isPNM(SDL_RWops *src)
   249 {
   250 	return(0);
   251 }
   252 
   253 /* Load a PNM type image from an SDL datasource */
   254 SDL_Surface *IMG_LoadPNM_RW(SDL_RWops *src)
   255 {
   256 	return(NULL);
   257 }
   258 
   259 #endif /* LOAD_PNM */