sdl_pixels.c

MPEG-4编解码的实现(包括MPEG4视音频编解码)

	pitch = (pitch + 3) & ~3;	/* 4-byte aligning */
	return(pitch);
}
/*
 * Match an RGB value to a particular palette index
 */
Uint8 SDL_FindColor(SDL_Palette *pal, Uint8 r, Uint8 g, Uint8 b)
{
	/* Do colorspace distance matching */
	unsigned int smallest;
	unsigned int distance;
	int rd, gd, bd;
	int i;
	Uint8 pixel=0;
		
	smallest = ~0;
	for ( i=0; i<pal->ncolors; ++i ) {
		rd = pal->colors[i].r - r;
		gd = pal->colors[i].g - g;
		bd = pal->colors[i].b - b;
		distance = (rd*rd)+(gd*gd)+(bd*bd);
		if ( distance < smallest ) {
			pixel = i;
			if ( distance == 0 ) { /* Perfect match! */
				break;
			}
			smallest = distance;
		}
	}
	return(pixel);
}

/* Find the opaque pixel value corresponding to an RGB triple */
Uint32 SDL_MapRGB(SDL_PixelFormat *format, Uint8 r, Uint8 g, Uint8 b)
{
	if ( format->palette == NULL ) {
		return (r >> format->Rloss) << format->Rshift
		       | (g >> format->Gloss) << format->Gshift
		       | (b >> format->Bloss) << format->Bshift
		       | format->Amask;
	} else {
		return SDL_FindColor(format->palette, r, g, b);
	}
}

/* Find the pixel value corresponding to an RGBA quadruple */
Uint32 SDL_MapRGBA(SDL_PixelFormat *format, Uint8 r, Uint8 g, Uint8 b, Uint8 a)
{
	if ( format->palette == NULL ) {
	        return (r >> format->Rloss) << format->Rshift
		    | (g >> format->Gloss) << format->Gshift
		    | (b >> format->Bloss) << format->Bshift
		    | ((a >> format->Aloss) << format->Ashift & format->Amask);
	} else {
		return SDL_FindColor(format->palette, r, g, b);
	}
}

void SDL_GetRGBA(Uint32 pixel, SDL_PixelFormat *fmt,
		 Uint8 *r, Uint8 *g, Uint8 *b, Uint8 *a)
{
	if ( fmt->palette == NULL ) {
	        /*
		 * This makes sure that the result is mapped to the
		 * interval [0..255], and the maximum value for each
		 * component is 255. This is important to make sure
		 * that white is indeed reported as (255, 255, 255),
		 * and that opaque alpha is 255.
		 * This only works for RGB bit fields at least 4 bit
		 * wide, which is almost always the case.
		 */
	        unsigned rv, gv, bv, av;
		rv = (pixel & fmt->Rmask) >> fmt->Rshift;
		*r = (rv << fmt->Rloss) + (rv >> (8 - fmt->Rloss));
		gv = (pixel & fmt->Gmask) >> fmt->Gshift;
		*g = (gv << fmt->Gloss) + (gv >> (8 - fmt->Gloss));
		bv = (pixel & fmt->Bmask) >> fmt->Bshift;
		*b = (bv << fmt->Bloss) + (bv >> (8 - fmt->Bloss));
		if(fmt->Amask) {
		        av = (pixel & fmt->Amask) >> fmt->Ashift;
			*a = (av << fmt->Aloss) + (av >> (8 - fmt->Aloss));
		} else
		        *a = SDL_ALPHA_OPAQUE;
	} else {
		*r = fmt->palette->colors[pixel].r;
		*g = fmt->palette->colors[pixel].g;
		*b = fmt->palette->colors[pixel].b;
		*a = SDL_ALPHA_OPAQUE;
	}
}

void SDL_GetRGB(Uint32 pixel, SDL_PixelFormat *fmt, Uint8 *r,Uint8 *g,Uint8 *b)
{
	if ( fmt->palette == NULL ) {
	        /* the note for SDL_GetRGBA above applies here too */
	        unsigned rv, gv, bv;
		rv = (pixel & fmt->Rmask) >> fmt->Rshift;
		*r = (rv << fmt->Rloss) + (rv >> (8 - fmt->Rloss));
		gv = (pixel & fmt->Gmask) >> fmt->Gshift;
		*g = (gv << fmt->Gloss) + (gv >> (8 - fmt->Gloss));
		bv = (pixel & fmt->Bmask) >> fmt->Bshift;
		*b = (bv << fmt->Bloss) + (bv >> (8 - fmt->Bloss));
	} else {
		*r = fmt->palette->colors[pixel].r;
		*g = fmt->palette->colors[pixel].g;
		*b = fmt->palette->colors[pixel].b;
	}
}

/* Apply gamma to a set of colors - this is easy. :) */
void SDL_ApplyGamma(Uint16 *gamma, SDL_Color *colors, SDL_Color *output,
							int ncolors)
{
	int i;

	for ( i=0; i<ncolors; ++i ) {
		output[i].r = gamma[0*256 + colors[i].r] >> 8;
		output[i].g = gamma[1*256 + colors[i].g] >> 8;
		output[i].b = gamma[2*256 + colors[i].b] >> 8;
	}
}

/* Map from Palette to Palette */
static Uint8 *Map1to1(SDL_Palette *src, SDL_Palette *dst, int *identical)
{
	Uint8 *map;
	int i;

	if ( identical ) {
		if ( src->ncolors <= dst->ncolors ) {
			/* If an identical palette, no need to map */
			if ( memcmp(src->colors, dst->colors, src->ncolors*
						sizeof(SDL_Color)) == 0 ) {
				*identical = 1;
				return(NULL);
			}
		}
		*identical = 0;
	}
	map = (Uint8 *)malloc(src->ncolors);
	if ( map == NULL ) {
		SDL_OutOfMemory();
		return(NULL);
	}
	for ( i=0; i<src->ncolors; ++i ) {
		map[i] = SDL_FindColor(dst,
			src->colors[i].r, src->colors[i].g, src->colors[i].b);
	}
	return(map);
}
/* Map from Palette to BitField */
static Uint8 *Map1toN(SDL_Palette *src, SDL_PixelFormat *dst)
{
	Uint8 *map;
	int i;
	int  bpp;
	unsigned alpha;

	bpp = ((dst->BytesPerPixel == 3) ? 4 : dst->BytesPerPixel);
	map = (Uint8 *)malloc(src->ncolors*bpp);
	if ( map == NULL ) {
		SDL_OutOfMemory();
		return(NULL);
	}

	alpha = dst->Amask ? SDL_ALPHA_OPAQUE : 0;
	/* We memory copy to the pixel map so the endianness is preserved */
	for ( i=0; i<src->ncolors; ++i ) {
		ASSEMBLE_RGBA(&map[i*bpp], dst->BytesPerPixel, dst,
			      src->colors[i].r, src->colors[i].g,
			      src->colors[i].b, alpha);
	}
	return(map);
}
/* Map from BitField to Dithered-Palette to Palette */
static Uint8 *MapNto1(SDL_PixelFormat *src, SDL_Palette *dst, int *identical)
{
	/* Generate a 256 color dither palette */
	SDL_Palette dithered;
	SDL_Color colors[256];

	dithered.ncolors = 256;
	SDL_DitherColors(colors, 8);
	dithered.colors = colors;
	return(Map1to1(&dithered, dst, identical));
}

SDL_BlitMap *SDL_AllocBlitMap(void)
{
	SDL_BlitMap *map;

	/* Allocate the empty map */
	map = (SDL_BlitMap *)malloc(sizeof(*map));
	if ( map == NULL ) {
		SDL_OutOfMemory();
		return(NULL);
	}
	memset(map, 0, sizeof(*map));

	/* Allocate the software blit data */
	map->sw_data = (struct private_swaccel *)malloc(sizeof(*map->sw_data));
	if ( map->sw_data == NULL ) {
		SDL_FreeBlitMap(map);
		SDL_OutOfMemory();
		return(NULL);
	}
	memset(map->sw_data, 0, sizeof(*map->sw_data));

	/* It's ready to go */
	return(map);
}
void SDL_InvalidateMap(SDL_BlitMap *map)
{
	if ( ! map ) {
		return;
	}
	map->dst = NULL;
	map->format_version = (unsigned int)-1;
	if ( map->table ) {
		free(map->table);
		map->table = NULL;
	}
}
int SDL_MapSurface (SDL_Surface *src, SDL_Surface *dst)
{
	SDL_PixelFormat *srcfmt;
	SDL_PixelFormat *dstfmt;
	SDL_BlitMap *map;

	/* Clear out any previous mapping */
	map = src->map;
	if ( (src->flags & SDL_RLEACCEL) == SDL_RLEACCEL ) {
		SDL_UnRLESurface(src, 1);
	}
	SDL_InvalidateMap(map);

	/* Figure out what kind of mapping we're doing */
	map->identity = 0;
	srcfmt = src->format;
	dstfmt = dst->format;
	switch (srcfmt->BytesPerPixel) {
	    case 1:
		switch (dstfmt->BytesPerPixel) {
		    case 1:
			/* Palette --> Palette */
			/* If both SDL_HWSURFACE, assume have same palette */
			if ( ((src->flags & SDL_HWSURFACE) == SDL_HWSURFACE) &&
			     ((dst->flags & SDL_HWSURFACE) == SDL_HWSURFACE) ) {
				map->identity = 1;
			} else {
				map->table = Map1to1(srcfmt->palette,
					dstfmt->palette, &map->identity);
			}
			if ( ! map->identity ) {
				if ( map->table == NULL ) {
					return(-1);
				}
			}
			if (srcfmt->BitsPerPixel!=dstfmt->BitsPerPixel)
				map->identity = 0;
			break;

		    default:
			/* Palette --> BitField */
			map->table = Map1toN(srcfmt->palette, dstfmt);
			if ( map->table == NULL ) {
				return(-1);
			}
			break;
		}
		break;
	default:
		switch (dstfmt->BytesPerPixel) {
		    case 1:
			/* BitField --> Palette */
			map->table = MapNto1(srcfmt,
					dstfmt->palette, &map->identity);
			if ( ! map->identity ) {
				if ( map->table == NULL ) {
					return(-1);
				}
			}
			map->identity = 0;	/* Don't optimize to copy */
			break;
		    default:
			/* BitField --> BitField */
			if ( FORMAT_EQUAL(srcfmt, dstfmt) )
				map->identity = 1;
			break;
		}
		break;
	}

	map->dst = dst;
	map->format_version = dst->format_version;

	/* Choose your blitters wisely */
	return(SDL_CalculateBlit(src));
}
void SDL_FreeBlitMap(SDL_BlitMap *map)
{
	if ( map ) {
		SDL_InvalidateMap(map);
		if ( map->sw_data != NULL ) {
			free(map->sw_data);
		}
		free(map);
	}
}