src/video/SDL_pixels.c
author Ryan C. Gordon <icculus@icculus.org>
Fri, 06 Jan 2006 13:20:10 +0000
changeset 1234 73676c1f56ee
parent 1057 e9d23bb80140
child 1312 c9b51268668f
permissions -rw-r--r--
For sanity's sake, removed the '&' when passing copy_row array to asm.
     1 /*
     2     SDL - Simple DirectMedia Layer
     3     Copyright (C) 1997-2004 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 #ifdef SAVE_RCSID
    24 static char rcsid =
    25  "@(#) $Id$";
    26 #endif
    27 
    28 /* General (mostly internal) pixel/color manipulation routines for SDL */
    29 
    30 #include <stdio.h>
    31 #include <stdlib.h>
    32 #include <string.h>
    33 
    34 #include "SDL_error.h"
    35 #include "SDL_endian.h"
    36 #include "SDL_video.h"
    37 #include "SDL_sysvideo.h"
    38 #include "SDL_blit.h"
    39 #include "SDL_pixels_c.h"
    40 #include "SDL_RLEaccel_c.h"
    41 
    42 /* Helper functions */
    43 /*
    44  * Allocate a pixel format structure and fill it according to the given info.
    45  */
    46 SDL_PixelFormat *SDL_AllocFormat(int bpp,
    47 			Uint32 Rmask, Uint32 Gmask, Uint32 Bmask, Uint32 Amask)
    48 {
    49 	SDL_PixelFormat *format;
    50 	Uint32 mask;
    51 
    52 	/* Allocate an empty pixel format structure */
    53 	format = malloc(sizeof(*format));
    54 	if ( format == NULL ) {
    55 		SDL_OutOfMemory();
    56 		return(NULL);
    57 	}
    58 	memset(format, 0, sizeof(*format));
    59 	format->alpha = SDL_ALPHA_OPAQUE;
    60 
    61 	/* Set up the format */
    62 	format->BitsPerPixel = bpp;
    63 	format->BytesPerPixel = (bpp+7)/8;
    64 	if ( Rmask || Bmask || Gmask ) { /* Packed pixels with custom mask */
    65 		format->palette = NULL;
    66 		format->Rshift = 0;
    67 		format->Rloss = 8;
    68 		if ( Rmask ) {
    69 			for ( mask = Rmask; !(mask&0x01); mask >>= 1 )
    70 				++format->Rshift;
    71 			for ( ; (mask&0x01); mask >>= 1 )
    72 				--format->Rloss;
    73 		}
    74 		format->Gshift = 0;
    75 		format->Gloss = 8;
    76 		if ( Gmask ) {
    77 			for ( mask = Gmask; !(mask&0x01); mask >>= 1 )
    78 				++format->Gshift;
    79 			for ( ; (mask&0x01); mask >>= 1 )
    80 				--format->Gloss;
    81 		}
    82 		format->Bshift = 0;
    83 		format->Bloss = 8;
    84 		if ( Bmask ) {
    85 			for ( mask = Bmask; !(mask&0x01); mask >>= 1 )
    86 				++format->Bshift;
    87 			for ( ; (mask&0x01); mask >>= 1 )
    88 				--format->Bloss;
    89 		}
    90 		format->Ashift = 0;
    91 		format->Aloss = 8;
    92 		if ( Amask ) {
    93 			for ( mask = Amask; !(mask&0x01); mask >>= 1 )
    94 				++format->Ashift;
    95 			for ( ; (mask&0x01); mask >>= 1 )
    96 				--format->Aloss;
    97 		}
    98 		format->Rmask = Rmask;
    99 		format->Gmask = Gmask;
   100 		format->Bmask = Bmask;
   101 		format->Amask = Amask;
   102 	} else if ( bpp > 8 ) {		/* Packed pixels with standard mask */
   103 		/* R-G-B */
   104 		if ( bpp > 24 )
   105 			bpp = 24;
   106 		format->Rloss = 8-(bpp/3);
   107 		format->Gloss = 8-(bpp/3)-(bpp%3);
   108 		format->Bloss = 8-(bpp/3);
   109 		format->Rshift = ((bpp/3)+(bpp%3))+(bpp/3);
   110 		format->Gshift = (bpp/3);
   111 		format->Bshift = 0;
   112 		format->Rmask = ((0xFF>>format->Rloss)<<format->Rshift);
   113 		format->Gmask = ((0xFF>>format->Gloss)<<format->Gshift);
   114 		format->Bmask = ((0xFF>>format->Bloss)<<format->Bshift);
   115 	} else {
   116 		/* Palettized formats have no mask info */
   117 		format->Rloss = 8;
   118 		format->Gloss = 8;
   119 		format->Bloss = 8;
   120 		format->Aloss = 8;
   121 		format->Rshift = 0;
   122 		format->Gshift = 0;
   123 		format->Bshift = 0;
   124 		format->Ashift = 0;
   125 		format->Rmask = 0;
   126 		format->Gmask = 0;
   127 		format->Bmask = 0;
   128 		format->Amask = 0;
   129 	}
   130 	if ( bpp <= 8 ) {			/* Palettized mode */
   131 		int ncolors = 1<<bpp;
   132 #ifdef DEBUG_PALETTE
   133 		fprintf(stderr,"bpp=%d ncolors=%d\n",bpp,ncolors);
   134 #endif
   135 		format->palette = (SDL_Palette *)malloc(sizeof(SDL_Palette));
   136 		if ( format->palette == NULL ) {
   137 			SDL_FreeFormat(format);
   138 			SDL_OutOfMemory();
   139 			return(NULL);
   140 		}
   141 		(format->palette)->ncolors = ncolors;
   142 		(format->palette)->colors = (SDL_Color *)malloc(
   143 				(format->palette)->ncolors*sizeof(SDL_Color));
   144 		if ( (format->palette)->colors == NULL ) {
   145 			SDL_FreeFormat(format);
   146 			SDL_OutOfMemory();
   147 			return(NULL);
   148 		}
   149 		if ( Rmask || Bmask || Gmask ) {
   150 			/* create palette according to masks */
   151 			int i;
   152 			int Rm=0,Gm=0,Bm=0;
   153 			int Rw=0,Gw=0,Bw=0;
   154 #ifdef ENABLE_PALETTE_ALPHA
   155 			int Am=0,Aw=0;
   156 #endif
   157 			if(Rmask)
   158 			{
   159 				Rw=8-format->Rloss;
   160 				for(i=format->Rloss;i>0;i-=Rw)
   161 					Rm|=1<<i;
   162 			}
   163 #ifdef DEBUG_PALETTE
   164 			fprintf(stderr,"Rw=%d Rm=0x%02X\n",Rw,Rm);
   165 #endif
   166 			if(Gmask)
   167 			{
   168 				Gw=8-format->Gloss;
   169 				for(i=format->Gloss;i>0;i-=Gw)
   170 					Gm|=1<<i;
   171 			}
   172 #ifdef DEBUG_PALETTE
   173 			fprintf(stderr,"Gw=%d Gm=0x%02X\n",Gw,Gm);
   174 #endif
   175 			if(Bmask)
   176 			{
   177 				Bw=8-format->Bloss;
   178 				for(i=format->Bloss;i>0;i-=Bw)
   179 					Bm|=1<<i;
   180 			}
   181 #ifdef DEBUG_PALETTE
   182 			fprintf(stderr,"Bw=%d Bm=0x%02X\n",Bw,Bm);
   183 #endif
   184 #ifdef ENABLE_PALETTE_ALPHA
   185 			if(Amask)
   186 			{
   187 				Aw=8-format->Aloss;
   188 				for(i=format->Aloss;i>0;i-=Aw)
   189 					Am|=1<<i;
   190 			}
   191 # ifdef DEBUG_PALETTE
   192 			fprintf(stderr,"Aw=%d Am=0x%02X\n",Aw,Am);
   193 # endif
   194 #endif
   195 			for(i=0; i < ncolors; ++i) {
   196 				int r,g,b;
   197 				r=(i&Rmask)>>format->Rshift;
   198 				r=(r<<format->Rloss)|((r*Rm)>>Rw);
   199 				format->palette->colors[i].r=r;
   200 
   201 				g=(i&Gmask)>>format->Gshift;
   202 				g=(g<<format->Gloss)|((g*Gm)>>Gw);
   203 				format->palette->colors[i].g=g;
   204 
   205 				b=(i&Bmask)>>format->Bshift;
   206 				b=(b<<format->Bloss)|((b*Bm)>>Bw);
   207 				format->palette->colors[i].b=b;
   208 
   209 #ifdef ENABLE_PALETTE_ALPHA
   210 				a=(i&Amask)>>format->Ashift;
   211 				a=(a<<format->Aloss)|((a*Am)>>Aw);
   212 				format->palette->colors[i].unused=a;
   213 #else
   214 				format->palette->colors[i].unused=0;
   215 #endif
   216 			}
   217 		} else if ( ncolors == 2 ) {
   218 			/* Create a black and white bitmap palette */
   219 			format->palette->colors[0].r = 0xFF;
   220 			format->palette->colors[0].g = 0xFF;
   221 			format->palette->colors[0].b = 0xFF;
   222 			format->palette->colors[1].r = 0x00;
   223 			format->palette->colors[1].g = 0x00;
   224 			format->palette->colors[1].b = 0x00;
   225 		} else {
   226 			/* Create an empty palette */
   227 			memset((format->palette)->colors, 0,
   228 				(format->palette)->ncolors*sizeof(SDL_Color));
   229 		}
   230 	}
   231 	return(format);
   232 }
   233 SDL_PixelFormat *SDL_ReallocFormat(SDL_Surface *surface, int bpp,
   234 			Uint32 Rmask, Uint32 Gmask, Uint32 Bmask, Uint32 Amask)
   235 {
   236 	if ( surface->format ) {
   237 		SDL_FreeFormat(surface->format);
   238 		SDL_FormatChanged(surface);
   239 	}
   240 	surface->format = SDL_AllocFormat(bpp, Rmask, Gmask, Bmask, Amask);
   241 	return surface->format;
   242 }
   243 
   244 /*
   245  * Change any previous mappings from/to the new surface format
   246  */
   247 void SDL_FormatChanged(SDL_Surface *surface)
   248 {
   249 	static int format_version = 0;
   250 	++format_version;
   251 	if ( format_version < 0 ) { /* It wrapped... */
   252 		format_version = 1;
   253 	}
   254 	surface->format_version = format_version;
   255 	SDL_InvalidateMap(surface->map);
   256 }
   257 /*
   258  * Free a previously allocated format structure
   259  */
   260 void SDL_FreeFormat(SDL_PixelFormat *format)
   261 {
   262 	if ( format ) {
   263 		if ( format->palette ) {
   264 			if ( format->palette->colors ) {
   265 				free(format->palette->colors);
   266 			}
   267 			free(format->palette);
   268 		}
   269 		free(format);
   270 	}
   271 }
   272 /*
   273  * Calculate an 8-bit (3 red, 3 green, 2 blue) dithered palette of colors
   274  */
   275 void SDL_DitherColors(SDL_Color *colors, int bpp)
   276 {
   277 	int i;
   278 	if(bpp != 8)
   279 		return;		/* only 8bpp supported right now */
   280 
   281 	for(i = 0; i < 256; i++) {
   282 		int r, g, b;
   283 		/* map each bit field to the full [0, 255] interval,
   284 		   so 0 is mapped to (0, 0, 0) and 255 to (255, 255, 255) */
   285 		r = i & 0xe0;
   286 		r |= r >> 3 | r >> 6;
   287 		colors[i].r = r;
   288 		g = (i << 3) & 0xe0;
   289 		g |= g >> 3 | g >> 6;
   290 		colors[i].g = g;
   291 		b = i & 0x3;
   292 		b |= b << 2;
   293 		b |= b << 4;
   294 		colors[i].b = b;
   295 	}
   296 }
   297 /* 
   298  * Calculate the pad-aligned scanline width of a surface
   299  */
   300 Uint16 SDL_CalculatePitch(SDL_Surface *surface)
   301 {
   302 	Uint16 pitch;
   303 
   304 	/* Surface should be 4-byte aligned for speed */
   305 	pitch = surface->w*surface->format->BytesPerPixel;
   306 	switch (surface->format->BitsPerPixel) {
   307 		case 1:
   308 			pitch = (pitch+7)/8;
   309 			break;
   310 		case 4:
   311 			pitch = (pitch+1)/2;
   312 			break;
   313 		default:
   314 			break;
   315 	}
   316 	pitch = (pitch + 3) & ~3;	/* 4-byte aligning */
   317 	return(pitch);
   318 }
   319 /*
   320  * Match an RGB value to a particular palette index
   321  */
   322 Uint8 SDL_FindColor(SDL_Palette *pal, Uint8 r, Uint8 g, Uint8 b)
   323 {
   324 	/* Do colorspace distance matching */
   325 	unsigned int smallest;
   326 	unsigned int distance;
   327 	int rd, gd, bd;
   328 	int i;
   329 	Uint8 pixel=0;
   330 		
   331 	smallest = ~0;
   332 	for ( i=0; i<pal->ncolors; ++i ) {
   333 		rd = pal->colors[i].r - r;
   334 		gd = pal->colors[i].g - g;
   335 		bd = pal->colors[i].b - b;
   336 		distance = (rd*rd)+(gd*gd)+(bd*bd);
   337 		if ( distance < smallest ) {
   338 			pixel = i;
   339 			if ( distance == 0 ) { /* Perfect match! */
   340 				break;
   341 			}
   342 			smallest = distance;
   343 		}
   344 	}
   345 	return(pixel);
   346 }
   347 
   348 /* Find the opaque pixel value corresponding to an RGB triple */
   349 Uint32 SDL_MapRGB(SDL_PixelFormat *format, Uint8 r, Uint8 g, Uint8 b)
   350 {
   351 	if ( format->palette == NULL ) {
   352 		return (r >> format->Rloss) << format->Rshift
   353 		       | (g >> format->Gloss) << format->Gshift
   354 		       | (b >> format->Bloss) << format->Bshift
   355 		       | format->Amask;
   356 	} else {
   357 		return SDL_FindColor(format->palette, r, g, b);
   358 	}
   359 }
   360 
   361 /* Find the pixel value corresponding to an RGBA quadruple */
   362 Uint32 SDL_MapRGBA(SDL_PixelFormat *format, Uint8 r, Uint8 g, Uint8 b, Uint8 a)
   363 {
   364 	if ( format->palette == NULL ) {
   365 	        return (r >> format->Rloss) << format->Rshift
   366 		    | (g >> format->Gloss) << format->Gshift
   367 		    | (b >> format->Bloss) << format->Bshift
   368 		    | ((a >> format->Aloss) << format->Ashift & format->Amask);
   369 	} else {
   370 		return SDL_FindColor(format->palette, r, g, b);
   371 	}
   372 }
   373 
   374 void SDL_GetRGBA(Uint32 pixel, SDL_PixelFormat *fmt,
   375 		 Uint8 *r, Uint8 *g, Uint8 *b, Uint8 *a)
   376 {
   377 	if ( fmt->palette == NULL ) {
   378 	        /*
   379 		 * This makes sure that the result is mapped to the
   380 		 * interval [0..255], and the maximum value for each
   381 		 * component is 255. This is important to make sure
   382 		 * that white is indeed reported as (255, 255, 255),
   383 		 * and that opaque alpha is 255.
   384 		 * This only works for RGB bit fields at least 4 bit
   385 		 * wide, which is almost always the case.
   386 		 */
   387 	        unsigned v;
   388 		v = (pixel & fmt->Rmask) >> fmt->Rshift;
   389 		*r = (v << fmt->Rloss) + (v >> (8 - (fmt->Rloss << 1)));
   390 		v = (pixel & fmt->Gmask) >> fmt->Gshift;
   391 		*g = (v << fmt->Gloss) + (v >> (8 - (fmt->Gloss << 1)));
   392 		v = (pixel & fmt->Bmask) >> fmt->Bshift;
   393 		*b = (v << fmt->Bloss) + (v >> (8 - (fmt->Bloss << 1)));
   394 		if(fmt->Amask) {
   395 		        v = (pixel & fmt->Amask) >> fmt->Ashift;
   396 			*a = (v << fmt->Aloss) + (v >> (8 - (fmt->Aloss << 1)));
   397 		} else {
   398 		        *a = SDL_ALPHA_OPAQUE;
   399                 }
   400 	} else {
   401 		*r = fmt->palette->colors[pixel].r;
   402 		*g = fmt->palette->colors[pixel].g;
   403 		*b = fmt->palette->colors[pixel].b;
   404 		*a = SDL_ALPHA_OPAQUE;
   405 	}
   406 }
   407 
   408 void SDL_GetRGB(Uint32 pixel, SDL_PixelFormat *fmt, Uint8 *r,Uint8 *g,Uint8 *b)
   409 {
   410 	if ( fmt->palette == NULL ) {
   411 	        /* the note for SDL_GetRGBA above applies here too */
   412 	        unsigned v;
   413 		v = (pixel & fmt->Rmask) >> fmt->Rshift;
   414 		*r = (v << fmt->Rloss) + (v >> (8 - (fmt->Rloss << 1)));
   415 		v = (pixel & fmt->Gmask) >> fmt->Gshift;
   416 		*g = (v << fmt->Gloss) + (v >> (8 - (fmt->Gloss << 1)));
   417 		v = (pixel & fmt->Bmask) >> fmt->Bshift;
   418 		*b = (v << fmt->Bloss) + (v >> (8 - (fmt->Bloss << 1)));
   419 	} else {
   420 		*r = fmt->palette->colors[pixel].r;
   421 		*g = fmt->palette->colors[pixel].g;
   422 		*b = fmt->palette->colors[pixel].b;
   423 	}
   424 }
   425 
   426 /* Apply gamma to a set of colors - this is easy. :) */
   427 void SDL_ApplyGamma(Uint16 *gamma, SDL_Color *colors, SDL_Color *output,
   428 							int ncolors)
   429 {
   430 	int i;
   431 
   432 	for ( i=0; i<ncolors; ++i ) {
   433 		output[i].r = gamma[0*256 + colors[i].r] >> 8;
   434 		output[i].g = gamma[1*256 + colors[i].g] >> 8;
   435 		output[i].b = gamma[2*256 + colors[i].b] >> 8;
   436 	}
   437 }
   438 
   439 /* Map from Palette to Palette */
   440 static Uint8 *Map1to1(SDL_Palette *src, SDL_Palette *dst, int *identical)
   441 {
   442 	Uint8 *map;
   443 	int i;
   444 
   445 	if ( identical ) {
   446 		if ( src->ncolors <= dst->ncolors ) {
   447 			/* If an identical palette, no need to map */
   448 			if ( memcmp(src->colors, dst->colors, src->ncolors*
   449 						sizeof(SDL_Color)) == 0 ) {
   450 				*identical = 1;
   451 				return(NULL);
   452 			}
   453 		}
   454 		*identical = 0;
   455 	}
   456 	map = (Uint8 *)malloc(src->ncolors);
   457 	if ( map == NULL ) {
   458 		SDL_OutOfMemory();
   459 		return(NULL);
   460 	}
   461 	for ( i=0; i<src->ncolors; ++i ) {
   462 		map[i] = SDL_FindColor(dst,
   463 			src->colors[i].r, src->colors[i].g, src->colors[i].b);
   464 	}
   465 	return(map);
   466 }
   467 /* Map from Palette to BitField */
   468 static Uint8 *Map1toN(SDL_Palette *src, SDL_PixelFormat *dst)
   469 {
   470 	Uint8 *map;
   471 	int i;
   472 	int  bpp;
   473 	unsigned alpha;
   474 
   475 	bpp = ((dst->BytesPerPixel == 3) ? 4 : dst->BytesPerPixel);
   476 	map = (Uint8 *)malloc(src->ncolors*bpp);
   477 	if ( map == NULL ) {
   478 		SDL_OutOfMemory();
   479 		return(NULL);
   480 	}
   481 
   482 	alpha = dst->Amask ? SDL_ALPHA_OPAQUE : 0;
   483 	/* We memory copy to the pixel map so the endianness is preserved */
   484 	for ( i=0; i<src->ncolors; ++i ) {
   485 		ASSEMBLE_RGBA(&map[i*bpp], dst->BytesPerPixel, dst,
   486 			      src->colors[i].r, src->colors[i].g,
   487 			      src->colors[i].b, alpha);
   488 	}
   489 	return(map);
   490 }
   491 /* Map from BitField to Dithered-Palette to Palette */
   492 static Uint8 *MapNto1(SDL_PixelFormat *src, SDL_Palette *dst, int *identical)
   493 {
   494 	/* Generate a 256 color dither palette */
   495 	SDL_Palette dithered;
   496 	SDL_Color colors[256];
   497 	
   498 	/* SDL_DitherColors does not initialize the 'unused' component of colors,
   499 	   but Map1to1 compares it against dst, so we should initialize it. */  
   500 	memset(colors, 0, sizeof(colors));
   501 
   502 	dithered.ncolors = 256;
   503 	SDL_DitherColors(colors, 8);
   504 	dithered.colors = colors;
   505 	return(Map1to1(&dithered, dst, identical));
   506 }
   507 
   508 SDL_BlitMap *SDL_AllocBlitMap(void)
   509 {
   510 	SDL_BlitMap *map;
   511 
   512 	/* Allocate the empty map */
   513 	map = (SDL_BlitMap *)malloc(sizeof(*map));
   514 	if ( map == NULL ) {
   515 		SDL_OutOfMemory();
   516 		return(NULL);
   517 	}
   518 	memset(map, 0, sizeof(*map));
   519 
   520 	/* Allocate the software blit data */
   521 	map->sw_data = (struct private_swaccel *)malloc(sizeof(*map->sw_data));
   522 	if ( map->sw_data == NULL ) {
   523 		SDL_FreeBlitMap(map);
   524 		SDL_OutOfMemory();
   525 		return(NULL);
   526 	}
   527 	memset(map->sw_data, 0, sizeof(*map->sw_data));
   528 
   529 	/* It's ready to go */
   530 	return(map);
   531 }
   532 void SDL_InvalidateMap(SDL_BlitMap *map)
   533 {
   534 	if ( ! map ) {
   535 		return;
   536 	}
   537 	map->dst = NULL;
   538 	map->format_version = (unsigned int)-1;
   539 	if ( map->table ) {
   540 		free(map->table);
   541 		map->table = NULL;
   542 	}
   543 }
   544 int SDL_MapSurface (SDL_Surface *src, SDL_Surface *dst)
   545 {
   546 	SDL_PixelFormat *srcfmt;
   547 	SDL_PixelFormat *dstfmt;
   548 	SDL_BlitMap *map;
   549 
   550 	/* Clear out any previous mapping */
   551 	map = src->map;
   552 	if ( (src->flags & SDL_RLEACCEL) == SDL_RLEACCEL ) {
   553 		SDL_UnRLESurface(src, 1);
   554 	}
   555 	SDL_InvalidateMap(map);
   556 
   557 	/* Figure out what kind of mapping we're doing */
   558 	map->identity = 0;
   559 	srcfmt = src->format;
   560 	dstfmt = dst->format;
   561 	switch (srcfmt->BytesPerPixel) {
   562 	    case 1:
   563 		switch (dstfmt->BytesPerPixel) {
   564 		    case 1:
   565 			/* Palette --> Palette */
   566 			/* If both SDL_HWSURFACE, assume have same palette */
   567 			if ( ((src->flags & SDL_HWSURFACE) == SDL_HWSURFACE) &&
   568 			     ((dst->flags & SDL_HWSURFACE) == SDL_HWSURFACE) ) {
   569 				map->identity = 1;
   570 			} else {
   571 				map->table = Map1to1(srcfmt->palette,
   572 					dstfmt->palette, &map->identity);
   573 			}
   574 			if ( ! map->identity ) {
   575 				if ( map->table == NULL ) {
   576 					return(-1);
   577 				}
   578 			}
   579 			if (srcfmt->BitsPerPixel!=dstfmt->BitsPerPixel)
   580 				map->identity = 0;
   581 			break;
   582 
   583 		    default:
   584 			/* Palette --> BitField */
   585 			map->table = Map1toN(srcfmt->palette, dstfmt);
   586 			if ( map->table == NULL ) {
   587 				return(-1);
   588 			}
   589 			break;
   590 		}
   591 		break;
   592 	default:
   593 		switch (dstfmt->BytesPerPixel) {
   594 		    case 1:
   595 			/* BitField --> Palette */
   596 			map->table = MapNto1(srcfmt,
   597 					dstfmt->palette, &map->identity);
   598 			if ( ! map->identity ) {
   599 				if ( map->table == NULL ) {
   600 					return(-1);
   601 				}
   602 			}
   603 			map->identity = 0;	/* Don't optimize to copy */
   604 			break;
   605 		    default:
   606 			/* BitField --> BitField */
   607 			if ( FORMAT_EQUAL(srcfmt, dstfmt) )
   608 				map->identity = 1;
   609 			break;
   610 		}
   611 		break;
   612 	}
   613 
   614 	map->dst = dst;
   615 	map->format_version = dst->format_version;
   616 
   617 	/* Choose your blitters wisely */
   618 	return(SDL_CalculateBlit(src));
   619 }
   620 void SDL_FreeBlitMap(SDL_BlitMap *map)
   621 {
   622 	if ( map ) {
   623 		SDL_InvalidateMap(map);
   624 		if ( map->sw_data != NULL ) {
   625 			free(map->sw_data);
   626 		}
   627 		free(map);
   628 	}
   629 }