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      1 /*
      2     SDL - Simple DirectMedia Layer
      3     Copyright (C) 1997-2012 Sam Lantinga
      4 
      5     This library is free software; you can redistribute it and/or
      6     modify it under the terms of the GNU Lesser General Public
      7     License as published by the Free Software Foundation; either
      8     version 2.1 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     Lesser General Public License for more details.
     14 
     15     You should have received a copy of the GNU Lesser General Public
     16     License along with this library; if not, write to the Free Software
     17     Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
     18 
     19     Sam Lantinga
     20     slouken (at) libsdl.org
     21 */
     22 #include "SDL_config.h"
     23 
     24 /* General (mostly internal) pixel/color manipulation routines for SDL */
     25 
     26 #include "SDL_endian.h"
     27 #include "SDL_video.h"
     28 #include "SDL_sysvideo.h"
     29 #include "SDL_blit.h"
     30 #include "SDL_pixels_c.h"
     31 #include "SDL_RLEaccel_c.h"
     32 
     33 /* Helper functions */
     34 /*
     35  * Allocate a pixel format structure and fill it according to the given info.
     36  */
     37 SDL_PixelFormat *SDL_AllocFormat(int bpp,
     38 			Uint32 Rmask, Uint32 Gmask, Uint32 Bmask, Uint32 Amask)
     39 {
     40 	SDL_PixelFormat *format;
     41 	Uint32 mask;
     42 
     43 	/* Allocate an empty pixel format structure */
     44 	format = SDL_malloc(sizeof(*format));
     45 	if ( format == NULL ) {
     46 		SDL_OutOfMemory();
     47 		return(NULL);
     48 	}
     49 	SDL_memset(format, 0, sizeof(*format));
     50 	format->alpha = SDL_ALPHA_OPAQUE;
     51 
     52 	/* Set up the format */
     53 	format->BitsPerPixel = bpp;
     54 	format->BytesPerPixel = (bpp+7)/8;
     55 	if ( Rmask || Bmask || Gmask ) { /* Packed pixels with custom mask */
     56 		format->palette = NULL;
     57 		format->Rshift = 0;
     58 		format->Rloss = 8;
     59 		if ( Rmask ) {
     60 			for ( mask = Rmask; !(mask&0x01); mask >>= 1 )
     61 				++format->Rshift;
     62 			for ( ; (mask&0x01); mask >>= 1 )
     63 				--format->Rloss;
     64 		}
     65 		format->Gshift = 0;
     66 		format->Gloss = 8;
     67 		if ( Gmask ) {
     68 			for ( mask = Gmask; !(mask&0x01); mask >>= 1 )
     69 				++format->Gshift;
     70 			for ( ; (mask&0x01); mask >>= 1 )
     71 				--format->Gloss;
     72 		}
     73 		format->Bshift = 0;
     74 		format->Bloss = 8;
     75 		if ( Bmask ) {
     76 			for ( mask = Bmask; !(mask&0x01); mask >>= 1 )
     77 				++format->Bshift;
     78 			for ( ; (mask&0x01); mask >>= 1 )
     79 				--format->Bloss;
     80 		}
     81 		format->Ashift = 0;
     82 		format->Aloss = 8;
     83 		if ( Amask ) {
     84 			for ( mask = Amask; !(mask&0x01); mask >>= 1 )
     85 				++format->Ashift;
     86 			for ( ; (mask&0x01); mask >>= 1 )
     87 				--format->Aloss;
     88 		}
     89 		format->Rmask = Rmask;
     90 		format->Gmask = Gmask;
     91 		format->Bmask = Bmask;
     92 		format->Amask = Amask;
     93 	} else if ( bpp > 8 ) {		/* Packed pixels with standard mask */
     94 		/* R-G-B */
     95 		if ( bpp > 24 )
     96 			bpp = 24;
     97 		format->Rloss = 8-(bpp/3);
     98 		format->Gloss = 8-(bpp/3)-(bpp%3);
     99 		format->Bloss = 8-(bpp/3);
    100 		format->Rshift = ((bpp/3)+(bpp%3))+(bpp/3);
    101 		format->Gshift = (bpp/3);
    102 		format->Bshift = 0;
    103 		format->Rmask = ((0xFF>>format->Rloss)<<format->Rshift);
    104 		format->Gmask = ((0xFF>>format->Gloss)<<format->Gshift);
    105 		format->Bmask = ((0xFF>>format->Bloss)<<format->Bshift);
    106 	} else {
    107 		/* Palettized formats have no mask info */
    108 		format->Rloss = 8;
    109 		format->Gloss = 8;
    110 		format->Bloss = 8;
    111 		format->Aloss = 8;
    112 		format->Rshift = 0;
    113 		format->Gshift = 0;
    114 		format->Bshift = 0;
    115 		format->Ashift = 0;
    116 		format->Rmask = 0;
    117 		format->Gmask = 0;
    118 		format->Bmask = 0;
    119 		format->Amask = 0;
    120 	}
    121 	if ( bpp <= 8 ) {			/* Palettized mode */
    122 		int ncolors = 1<<bpp;
    123 #ifdef DEBUG_PALETTE
    124 		fprintf(stderr,"bpp=%d ncolors=%d\n",bpp,ncolors);
    125 #endif
    126 		format->palette = (SDL_Palette *)SDL_malloc(sizeof(SDL_Palette));
    127 		if ( format->palette == NULL ) {
    128 			SDL_FreeFormat(format);
    129 			SDL_OutOfMemory();
    130 			return(NULL);
    131 		}
    132 		(format->palette)->ncolors = ncolors;
    133 		(format->palette)->colors = (SDL_Color *)SDL_malloc(
    134 				(format->palette)->ncolors*sizeof(SDL_Color));
    135 		if ( (format->palette)->colors == NULL ) {
    136 			SDL_FreeFormat(format);
    137 			SDL_OutOfMemory();
    138 			return(NULL);
    139 		}
    140 		if ( Rmask || Bmask || Gmask ) {
    141 			/* create palette according to masks */
    142 			int i;
    143 			int Rm=0,Gm=0,Bm=0;
    144 			int Rw=0,Gw=0,Bw=0;
    145 #ifdef ENABLE_PALETTE_ALPHA
    146 			int Am=0,Aw=0;
    147 #endif
    148 			if(Rmask)
    149 			{
    150 				Rw=8-format->Rloss;
    151 				for(i=format->Rloss;i>0;i-=Rw)
    152 					Rm|=1<<i;
    153 			}
    154 #ifdef DEBUG_PALETTE
    155 			fprintf(stderr,"Rw=%d Rm=0x%02X\n",Rw,Rm);
    156 #endif
    157 			if(Gmask)
    158 			{
    159 				Gw=8-format->Gloss;
    160 				for(i=format->Gloss;i>0;i-=Gw)
    161 					Gm|=1<<i;
    162 			}
    163 #ifdef DEBUG_PALETTE
    164 			fprintf(stderr,"Gw=%d Gm=0x%02X\n",Gw,Gm);
    165 #endif
    166 			if(Bmask)
    167 			{
    168 				Bw=8-format->Bloss;
    169 				for(i=format->Bloss;i>0;i-=Bw)
    170 					Bm|=1<<i;
    171 			}
    172 #ifdef DEBUG_PALETTE
    173 			fprintf(stderr,"Bw=%d Bm=0x%02X\n",Bw,Bm);
    174 #endif
    175 #ifdef ENABLE_PALETTE_ALPHA
    176 			if(Amask)
    177 			{
    178 				Aw=8-format->Aloss;
    179 				for(i=format->Aloss;i>0;i-=Aw)
    180 					Am|=1<<i;
    181 			}
    182 # ifdef DEBUG_PALETTE
    183 			fprintf(stderr,"Aw=%d Am=0x%02X\n",Aw,Am);
    184 # endif
    185 #endif
    186 			for(i=0; i < ncolors; ++i) {
    187 				int r,g,b;
    188 				r=(i&Rmask)>>format->Rshift;
    189 				r=(r<<format->Rloss)|((r*Rm)>>Rw);
    190 				format->palette->colors[i].r=r;
    191 
    192 				g=(i&Gmask)>>format->Gshift;
    193 				g=(g<<format->Gloss)|((g*Gm)>>Gw);
    194 				format->palette->colors[i].g=g;
    195 
    196 				b=(i&Bmask)>>format->Bshift;
    197 				b=(b<<format->Bloss)|((b*Bm)>>Bw);
    198 				format->palette->colors[i].b=b;
    199 
    200 #ifdef ENABLE_PALETTE_ALPHA
    201 				a=(i&Amask)>>format->Ashift;
    202 				a=(a<<format->Aloss)|((a*Am)>>Aw);
    203 				format->palette->colors[i].unused=a;
    204 #else
    205 				format->palette->colors[i].unused=0;
    206 #endif
    207 			}
    208 		} else if ( ncolors == 2 ) {
    209 			/* Create a black and white bitmap palette */
    210 			format->palette->colors[0].r = 0xFF;
    211 			format->palette->colors[0].g = 0xFF;
    212 			format->palette->colors[0].b = 0xFF;
    213 			format->palette->colors[1].r = 0x00;
    214 			format->palette->colors[1].g = 0x00;
    215 			format->palette->colors[1].b = 0x00;
    216 		} else {
    217 			/* Create an empty palette */
    218 			SDL_memset((format->palette)->colors, 0,
    219 				(format->palette)->ncolors*sizeof(SDL_Color));
    220 		}
    221 	}
    222 	return(format);
    223 }
    224 SDL_PixelFormat *SDL_ReallocFormat(SDL_Surface *surface, int bpp,
    225 			Uint32 Rmask, Uint32 Gmask, Uint32 Bmask, Uint32 Amask)
    226 {
    227 	if ( surface->format ) {
    228 		SDL_FreeFormat(surface->format);
    229 		SDL_FormatChanged(surface);
    230 	}
    231 	surface->format = SDL_AllocFormat(bpp, Rmask, Gmask, Bmask, Amask);
    232 	return surface->format;
    233 }
    234 
    235 /*
    236  * Change any previous mappings from/to the new surface format
    237  */
    238 void SDL_FormatChanged(SDL_Surface *surface)
    239 {
    240 	static int format_version = 0;
    241 	++format_version;
    242 	if ( format_version < 0 ) { /* It wrapped... */
    243 		format_version = 1;
    244 	}
    245 	surface->format_version = format_version;
    246 	SDL_InvalidateMap(surface->map);
    247 }
    248 /*
    249  * Free a previously allocated format structure
    250  */
    251 void SDL_FreeFormat(SDL_PixelFormat *format)
    252 {
    253 	if ( format ) {
    254 		if ( format->palette ) {
    255 			if ( format->palette->colors ) {
    256 				SDL_free(format->palette->colors);
    257 			}
    258 			SDL_free(format->palette);
    259 		}
    260 		SDL_free(format);
    261 	}
    262 }
    263 /*
    264  * Calculate an 8-bit (3 red, 3 green, 2 blue) dithered palette of colors
    265  */
    266 void SDL_DitherColors(SDL_Color *colors, int bpp)
    267 {
    268 	int i;
    269 	if(bpp != 8)
    270 		return;		/* only 8bpp supported right now */
    271 
    272 	for(i = 0; i < 256; i++) {
    273 		int r, g, b;
    274 		/* map each bit field to the full [0, 255] interval,
    275 		   so 0 is mapped to (0, 0, 0) and 255 to (255, 255, 255) */
    276 		r = i & 0xe0;
    277 		r |= r >> 3 | r >> 6;
    278 		colors[i].r = r;
    279 		g = (i << 3) & 0xe0;
    280 		g |= g >> 3 | g >> 6;
    281 		colors[i].g = g;
    282 		b = i & 0x3;
    283 		b |= b << 2;
    284 		b |= b << 4;
    285 		colors[i].b = b;
    286 	}
    287 }
    288 /*
    289  * Calculate the pad-aligned scanline width of a surface
    290  */
    291 Uint16 SDL_CalculatePitch(SDL_Surface *surface)
    292 {
    293 	Uint16 pitch;
    294 
    295 	/* Surface should be 4-byte aligned for speed */
    296 	pitch = surface->w*surface->format->BytesPerPixel;
    297 	switch (surface->format->BitsPerPixel) {
    298 		case 1:
    299 			pitch = (pitch+7)/8;
    300 			break;
    301 		case 4:
    302 			pitch = (pitch+1)/2;
    303 			break;
    304 		default:
    305 			break;
    306 	}
    307 	pitch = (pitch + 3) & ~3;	/* 4-byte aligning */
    308 	return(pitch);
    309 }
    310 /*
    311  * Match an RGB value to a particular palette index
    312  */
    313 Uint8 SDL_FindColor(SDL_Palette *pal, Uint8 r, Uint8 g, Uint8 b)
    314 {
    315 	/* Do colorspace distance matching */
    316 	unsigned int smallest;
    317 	unsigned int distance;
    318 	int rd, gd, bd;
    319 	int i;
    320 	Uint8 pixel=0;
    321 
    322 	smallest = ~0;
    323 	for ( i=0; i<pal->ncolors; ++i ) {
    324 		rd = pal->colors[i].r - r;
    325 		gd = pal->colors[i].g - g;
    326 		bd = pal->colors[i].b - b;
    327 		distance = (rd*rd)+(gd*gd)+(bd*bd);
    328 		if ( distance < smallest ) {
    329 			pixel = i;
    330 			if ( distance == 0 ) { /* Perfect match! */
    331 				break;
    332 			}
    333 			smallest = distance;
    334 		}
    335 	}
    336 	return(pixel);
    337 }
    338 
    339 /* Find the opaque pixel value corresponding to an RGB triple */
    340 Uint32 SDL_MapRGB
    341 (const SDL_PixelFormat * const format,
    342  const Uint8 r, const Uint8 g, const Uint8 b)
    343 {
    344 	if ( format->palette == NULL ) {
    345 		return (r >> format->Rloss) << format->Rshift
    346 		       | (g >> format->Gloss) << format->Gshift
    347 		       | (b >> format->Bloss) << format->Bshift
    348 		       | format->Amask;
    349 	} else {
    350 		return SDL_FindColor(format->palette, r, g, b);
    351 	}
    352 }
    353 
    354 /* Find the pixel value corresponding to an RGBA quadruple */
    355 Uint32 SDL_MapRGBA
    356 (const SDL_PixelFormat * const format,
    357  const Uint8 r, const Uint8 g, const Uint8 b, const Uint8 a)
    358 {
    359 	if ( format->palette == NULL ) {
    360 	        return (r >> format->Rloss) << format->Rshift
    361 		    | (g >> format->Gloss) << format->Gshift
    362 		    | (b >> format->Bloss) << format->Bshift
    363 		    | ((a >> format->Aloss) << format->Ashift & format->Amask);
    364 	} else {
    365 		return SDL_FindColor(format->palette, r, g, b);
    366 	}
    367 }
    368 
    369 void SDL_GetRGBA(Uint32 pixel, const SDL_PixelFormat * const fmt,
    370 		 Uint8 *r, Uint8 *g, Uint8 *b, Uint8 *a)
    371 {
    372 	if ( fmt->palette == NULL ) {
    373 	        /*
    374 		 * This makes sure that the result is mapped to the
    375 		 * interval [0..255], and the maximum value for each
    376 		 * component is 255. This is important to make sure
    377 		 * that white is indeed reported as (255, 255, 255),
    378 		 * and that opaque alpha is 255.
    379 		 * This only works for RGB bit fields at least 4 bit
    380 		 * wide, which is almost always the case.
    381 		 */
    382 	        unsigned v;
    383 		v = (pixel & fmt->Rmask) >> fmt->Rshift;
    384 		*r = (v << fmt->Rloss) + (v >> (8 - (fmt->Rloss << 1)));
    385 		v = (pixel & fmt->Gmask) >> fmt->Gshift;
    386 		*g = (v << fmt->Gloss) + (v >> (8 - (fmt->Gloss << 1)));
    387 		v = (pixel & fmt->Bmask) >> fmt->Bshift;
    388 		*b = (v << fmt->Bloss) + (v >> (8 - (fmt->Bloss << 1)));
    389 		if(fmt->Amask) {
    390 		        v = (pixel & fmt->Amask) >> fmt->Ashift;
    391 			*a = (v << fmt->Aloss) + (v >> (8 - (fmt->Aloss << 1)));
    392 		} else {
    393 		        *a = SDL_ALPHA_OPAQUE;
    394                 }
    395 	} else {
    396 		*r = fmt->palette->colors[pixel].r;
    397 		*g = fmt->palette->colors[pixel].g;
    398 		*b = fmt->palette->colors[pixel].b;
    399 		*a = SDL_ALPHA_OPAQUE;
    400 	}
    401 }
    402 
    403 void SDL_GetRGB(Uint32 pixel, const SDL_PixelFormat * const fmt,
    404                 Uint8 *r,Uint8 *g,Uint8 *b)
    405 {
    406 	if ( fmt->palette == NULL ) {
    407 	        /* the note for SDL_GetRGBA above applies here too */
    408 	        unsigned v;
    409 		v = (pixel & fmt->Rmask) >> fmt->Rshift;
    410 		*r = (v << fmt->Rloss) + (v >> (8 - (fmt->Rloss << 1)));
    411 		v = (pixel & fmt->Gmask) >> fmt->Gshift;
    412 		*g = (v << fmt->Gloss) + (v >> (8 - (fmt->Gloss << 1)));
    413 		v = (pixel & fmt->Bmask) >> fmt->Bshift;
    414 		*b = (v << fmt->Bloss) + (v >> (8 - (fmt->Bloss << 1)));
    415 	} else {
    416 		*r = fmt->palette->colors[pixel].r;
    417 		*g = fmt->palette->colors[pixel].g;
    418 		*b = fmt->palette->colors[pixel].b;
    419 	}
    420 }
    421 
    422 /* Apply gamma to a set of colors - this is easy. :) */
    423 void SDL_ApplyGamma(Uint16 *gamma, SDL_Color *colors, SDL_Color *output,
    424 							int ncolors)
    425 {
    426 	int i;
    427 
    428 	for ( i=0; i<ncolors; ++i ) {
    429 		output[i].r = gamma[0*256 + colors[i].r] >> 8;
    430 		output[i].g = gamma[1*256 + colors[i].g] >> 8;
    431 		output[i].b = gamma[2*256 + colors[i].b] >> 8;
    432 	}
    433 }
    434 
    435 /* Map from Palette to Palette */
    436 static Uint8 *Map1to1(SDL_Palette *src, SDL_Palette *dst, int *identical)
    437 {
    438 	Uint8 *map;
    439 	int i;
    440 
    441 	if ( identical ) {
    442 		if ( src->ncolors <= dst->ncolors ) {
    443 			/* If an identical palette, no need to map */
    444 			if ( SDL_memcmp(src->colors, dst->colors, src->ncolors*
    445 						sizeof(SDL_Color)) == 0 ) {
    446 				*identical = 1;
    447 				return(NULL);
    448 			}
    449 		}
    450 		*identical = 0;
    451 	}
    452 	map = (Uint8 *)SDL_malloc(src->ncolors);
    453 	if ( map == NULL ) {
    454 		SDL_OutOfMemory();
    455 		return(NULL);
    456 	}
    457 	for ( i=0; i<src->ncolors; ++i ) {
    458 		map[i] = SDL_FindColor(dst,
    459 			src->colors[i].r, src->colors[i].g, src->colors[i].b);
    460 	}
    461 	return(map);
    462 }
    463 /* Map from Palette to BitField */
    464 static Uint8 *Map1toN(SDL_PixelFormat *src, SDL_PixelFormat *dst)
    465 {
    466 	Uint8 *map;
    467 	int i;
    468 	int  bpp;
    469 	unsigned alpha;
    470 	SDL_Palette *pal = src->palette;
    471 
    472 	bpp = ((dst->BytesPerPixel == 3) ? 4 : dst->BytesPerPixel);
    473 	map = (Uint8 *)SDL_malloc(pal->ncolors*bpp);
    474 	if ( map == NULL ) {
    475 		SDL_OutOfMemory();
    476 		return(NULL);
    477 	}
    478 
    479 	alpha = dst->Amask ? src->alpha : 0;
    480 	/* We memory copy to the pixel map so the endianness is preserved */
    481 	for ( i=0; i<pal->ncolors; ++i ) {
    482 		ASSEMBLE_RGBA(&map[i*bpp], dst->BytesPerPixel, dst,
    483 			      pal->colors[i].r, pal->colors[i].g,
    484 			      pal->colors[i].b, alpha);
    485 	}
    486 	return(map);
    487 }
    488 /* Map from BitField to Dithered-Palette to Palette */
    489 static Uint8 *MapNto1(SDL_PixelFormat *src, SDL_PixelFormat *dst, int *identical)
    490 {
    491 	/* Generate a 256 color dither palette */
    492 	SDL_Palette dithered;
    493 	SDL_Color colors[256];
    494 	SDL_Palette *pal = dst->palette;
    495 
    496 	/* SDL_DitherColors does not initialize the 'unused' component of colors,
    497 	   but Map1to1 compares it against pal, so we should initialize it. */
    498 	SDL_memset(colors, 0, sizeof(colors));
    499 
    500 	dithered.ncolors = 256;
    501 	SDL_DitherColors(colors, 8);
    502 	dithered.colors = colors;
    503 	return(Map1to1(&dithered, pal, identical));
    504 }
    505 
    506 SDL_BlitMap *SDL_AllocBlitMap(void)
    507 {
    508 	SDL_BlitMap *map;
    509 
    510 	/* Allocate the empty map */
    511 	map = (SDL_BlitMap *)SDL_malloc(sizeof(*map));
    512 	if ( map == NULL ) {
    513 		SDL_OutOfMemory();
    514 		return(NULL);
    515 	}
    516 	SDL_memset(map, 0, sizeof(*map));
    517 
    518 	/* Allocate the software blit data */
    519 	map->sw_data = (struct private_swaccel *)SDL_malloc(sizeof(*map->sw_data));
    520 	if ( map->sw_data == NULL ) {
    521 		SDL_FreeBlitMap(map);
    522 		SDL_OutOfMemory();
    523 		return(NULL);
    524 	}
    525 	SDL_memset(map->sw_data, 0, sizeof(*map->sw_data));
    526 
    527 	/* It's ready to go */
    528 	return(map);
    529 }
    530 void SDL_InvalidateMap(SDL_BlitMap *map)
    531 {
    532 	if ( ! map ) {
    533 		return;
    534 	}
    535 	map->dst = NULL;
    536 	map->format_version = (unsigned int)-1;
    537 	if ( map->table ) {
    538 		SDL_free(map->table);
    539 		map->table = NULL;
    540 	}
    541 }
    542 int SDL_MapSurface (SDL_Surface *src, SDL_Surface *dst)
    543 {
    544 	SDL_PixelFormat *srcfmt;
    545 	SDL_PixelFormat *dstfmt;
    546 	SDL_BlitMap *map;
    547 
    548 	/* Clear out any previous mapping */
    549 	map = src->map;
    550 	if ( (src->flags & SDL_RLEACCEL) == SDL_RLEACCEL ) {
    551 		SDL_UnRLESurface(src, 1);
    552 	}
    553 	SDL_InvalidateMap(map);
    554 
    555 	/* Figure out what kind of mapping we're doing */
    556 	map->identity = 0;
    557 	srcfmt = src->format;
    558 	dstfmt = dst->format;
    559 	switch (srcfmt->BytesPerPixel) {
    560 	    case 1:
    561 		switch (dstfmt->BytesPerPixel) {
    562 		    case 1:
    563 			/* Palette --> Palette */
    564 			/* If both SDL_HWSURFACE, assume have same palette */
    565 			if ( ((src->flags & SDL_HWSURFACE) == SDL_HWSURFACE) &&
    566 			     ((dst->flags & SDL_HWSURFACE) == SDL_HWSURFACE) ) {
    567 				map->identity = 1;
    568 			} else {
    569 				map->table = Map1to1(srcfmt->palette,
    570 					dstfmt->palette, &map->identity);
    571 			}
    572 			if ( ! map->identity ) {
    573 				if ( map->table == NULL ) {
    574 					return(-1);
    575 				}
    576 			}
    577 			if (srcfmt->BitsPerPixel!=dstfmt->BitsPerPixel)
    578 				map->identity = 0;
    579 			break;
    580 
    581 		    default:
    582 			/* Palette --> BitField */
    583 			map->table = Map1toN(srcfmt, dstfmt);
    584 			if ( map->table == NULL ) {
    585 				return(-1);
    586 			}
    587 			break;
    588 		}
    589 		break;
    590 	default:
    591 		switch (dstfmt->BytesPerPixel) {
    592 		    case 1:
    593 			/* BitField --> Palette */
    594 			map->table = MapNto1(srcfmt, dstfmt, &map->identity);
    595 			if ( ! map->identity ) {
    596 				if ( map->table == NULL ) {
    597 					return(-1);
    598 				}
    599 			}
    600 			map->identity = 0;	/* Don't optimize to copy */
    601 			break;
    602 		    default:
    603 			/* BitField --> BitField */
    604 			if ( FORMAT_EQUAL(srcfmt, dstfmt) )
    605 				map->identity = 1;
    606 			break;
    607 		}
    608 		break;
    609 	}
    610 
    611 	map->dst = dst;
    612 	map->format_version = dst->format_version;
    613 
    614 	/* Choose your blitters wisely */
    615 	return(SDL_CalculateBlit(src));
    616 }
    617 void SDL_FreeBlitMap(SDL_BlitMap *map)
    618 {
    619 	if ( map ) {
    620 		SDL_InvalidateMap(map);
    621 		if ( map->sw_data != NULL ) {
    622 			SDL_free(map->sw_data);
    623 		}
    624 		SDL_free(map);
    625 	}
    626 }
    627