img_pcx.c

It is extension program for SDL to display images other than bmp, but all the other formats.

/*
    SDL_image:  An example image loading library for use with SDL
    Copyright (C) 1997-2006 Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 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
    Lesser General Public License for more details.

    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

    Sam Lantinga
    [e-mail]
*/

/*
 * PCX file reader:
 * Supports:
 *  1..4 bits/pixel in multiplanar format (1 bit/plane/pixel)
 *  8 bits/pixel in single-planar format (8 bits/plane/pixel)
 *  24 bits/pixel in 3-plane format (8 bits/plane/pixel)
 *
 * (The <8bpp formats are expanded to 8bpp surfaces)
 *
 * Doesn't support:
 *  single-planar packed-pixel formats other than 8bpp
 *  4-plane 32bpp format with a fourth "intensity" plane
 */
#include <stdio.h>
#include <stdlib.h>

#include "SDL_endian.h"

#include "SDL_image.h"

#ifdef LOAD_PCX

struct PCXheader {
	Uint8 Manufacturer;
	Uint8 Version;
	Uint8 Encoding;
	Uint8 BitsPerPixel;
	Sint16 Xmin, Ymin, Xmax, Ymax;
	Sint16 HDpi, VDpi;
	Uint8 Colormap[48];
	Uint8 Reserved;
	Uint8 NPlanes;
	Sint16 BytesPerLine;
	Sint16 PaletteInfo;
	Sint16 HscreenSize;
	Sint16 VscreenSize;
	Uint8 Filler[54];
};

/* See if an image is contained in a data source */
int IMG_isPCX(SDL_RWops *src)
{
	int start;
	int is_PCX;
	const int ZSoft_Manufacturer = 10;
	const int PC_Paintbrush_Version = 5;
	const int PCX_RunLength_Encoding = 1;
	struct PCXheader pcxh;

	if ( !src )
		return 0;
	start = SDL_RWtell(src);
	is_PCX = 0;
	if ( SDL_RWread(src, &pcxh, sizeof(pcxh), 1) == 1 ) {
		if ( (pcxh.Manufacturer == ZSoft_Manufacturer) &&
		     (pcxh.Version == PC_Paintbrush_Version) &&
		     (pcxh.Encoding == PCX_RunLength_Encoding) ) {
			is_PCX = 1;
		}
	}
	SDL_RWseek(src, start, SEEK_SET);
	return(is_PCX);
}

/* Load a PCX type image from an SDL datasource */
SDL_Surface *IMG_LoadPCX_RW(SDL_RWops *src)
{
	int start;
	struct PCXheader pcxh;
	Uint32 Rmask;
	Uint32 Gmask;
	Uint32 Bmask;
	Uint32 Amask;
	SDL_Surface *surface = NULL;
	int width, height;
	int y, bpl;
	Uint8 *row, *buf = NULL;
	char *error = NULL;
	int bits, src_bits;

	if ( !src ) {
		/* The error message has been set in SDL_RWFromFile */
		return NULL;
	}
	start = SDL_RWtell(src);

	if ( ! SDL_RWread(src, &pcxh, sizeof(pcxh), 1) ) {
		error = "file truncated";
		goto done;
	}
	pcxh.Xmin = SDL_SwapLE16(pcxh.Xmin);
	pcxh.Ymin = SDL_SwapLE16(pcxh.Ymin);
	pcxh.Xmax = SDL_SwapLE16(pcxh.Xmax);
	pcxh.Ymax = SDL_SwapLE16(pcxh.Ymax);
	pcxh.BytesPerLine = SDL_SwapLE16(pcxh.BytesPerLine);

	/* Create the surface of the appropriate type */
	width = (pcxh.Xmax - pcxh.Xmin) + 1;
	height = (pcxh.Ymax - pcxh.Ymin) + 1;
	Rmask = Gmask = Bmask = Amask = 0;
	src_bits = pcxh.BitsPerPixel * pcxh.NPlanes;
	if((pcxh.BitsPerPixel == 1 && pcxh.NPlanes >= 1 && pcxh.NPlanes <= 4)
	   || (pcxh.BitsPerPixel == 8 && pcxh.NPlanes == 1)) {
		bits = 8;
	} else if(pcxh.BitsPerPixel == 8 && pcxh.NPlanes == 3) {
		bits = 24;
		if ( SDL_BYTEORDER == SDL_LIL_ENDIAN ) {
			Rmask = 0x000000FF;
			Gmask = 0x0000FF00;
			Bmask = 0x00FF0000;
		} else {
			Rmask = 0xFF0000;
			Gmask = 0x00FF00;
			Bmask = 0x0000FF;
		}
	} else {
		error = "unsupported PCX format";
		goto done;
	}
	surface = SDL_AllocSurface(SDL_SWSURFACE, width, height,
				   bits, Rmask, Gmask, Bmask, Amask);
	if ( surface == NULL )
		goto done;

	bpl = pcxh.NPlanes * pcxh.BytesPerLine;
	buf = malloc(bpl);
	row = surface->pixels;
	for ( y=0; y<surface->h; ++y ) {
		/* decode a scan line to a temporary buffer first */
		int i, count = 0;
		Uint8 ch;
		Uint8 *dst = (src_bits == 8) ? row : buf;
		for(i = 0; i < bpl; i++) {
			if(!count) {
				if(!SDL_RWread(src, &ch, 1, 1)) {
					error = "file truncated";
					goto done;
				}
				if( (ch & 0xc0) == 0xc0) {
					count = ch & 0x3f;
					if(!SDL_RWread(src, &ch, 1, 1)) {
						error = "file truncated";
						goto done;
					}
				} else
					count = 1;
			}
			dst[i] = ch;
			count--;
		}

		if(src_bits <= 4) {
			/* expand planes to 1 byte/pixel */
			Uint8 *src = buf;
			int plane;
			for(plane = 0; plane < pcxh.NPlanes; plane++) {
				int i, j, x = 0;
				for(i = 0; i < pcxh.BytesPerLine; i++) {
					Uint8 byte = *src++;
					for(j = 7; j >= 0; j--) {
						unsigned bit = (byte >> j) & 1;
						/* skip padding bits */
						if (i * 8 + j >= width)
							continue;
						row[x++] |= bit << plane;
					}
				}
			}
 		} else if(src_bits == 24) {
			/* de-interlace planes */
			Uint8 *src = buf;
			int plane;
			for(plane = 0; plane < pcxh.NPlanes; plane++) {
				int x;
				dst = row + plane;
				for(x = 0; x < width; x++) {
					*dst = *src++;
					dst += pcxh.NPlanes;
				}
			}
		}

		row += surface->pitch;
	}

	if(bits == 8) {
		SDL_Color *colors = surface->format->palette->colors;
		int nc = 1 << src_bits;
		int i;

		surface->format->palette->ncolors = nc;
		if(src_bits == 8) {
			Uint8 ch;
			/* look for a 256-colour palette */
			do {
				if ( !SDL_RWread(src, &ch, 1, 1)) {
					error = "file truncated";
					goto done;
				}
			} while ( ch != 12 );

			for(i = 0; i < 256; i++) {
				SDL_RWread(src, &colors[i].r, 1, 1);
				SDL_RWread(src, &colors[i].g, 1, 1);
				SDL_RWread(src, &colors[i].b, 1, 1);
			}
		} else {
			for(i = 0; i < nc; i++) {
				colors[i].r = pcxh.Colormap[i * 3];
				colors[i].g = pcxh.Colormap[i * 3 + 1];
				colors[i].b = pcxh.Colormap[i * 3 + 2];
			}
		}
	}

done:
	free(buf);
	if ( error ) {
		SDL_RWseek(src, start, SEEK_SET);
		if ( surface ) {
			SDL_FreeSurface(surface);
			surface = NULL;
		}
		IMG_SetError(error);
	}
	return(surface);
}

#else

/* See if an image is contained in a data source */
int IMG_isPCX(SDL_RWops *src)
{
	return(0);
}

/* Load a PCX type image from an SDL datasource */
SDL_Surface *IMG_LoadPCX_RW(SDL_RWops *src)
{
	return(NULL);
}

#endif /* LOAD_PCX */