sdl_pixels.c

Simple DirectMedia Layer - Simple DirectMedia Layer 是一个跨平台的多媒体库设计用来提供快速图形framebuffer和音频驱动。应用MPEG为软件

/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002  Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 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
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public
    License along with this library; if not, write to the Free
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    Sam Lantinga
    [e-mail]
*/

#ifdef SAVE_RCSID
static char rcsid =
 "@(#) $Id: SDL_pixels.c,v 1.6 2002/03/06 11:23:03 slouken Exp $";
#endif

/* General (mostly internal) pixel/color manipulation routines for SDL */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "SDL_error.h"
#include "SDL_endian.h"
#include "SDL_video.h"
#include "SDL_sysvideo.h"
#include "SDL_blit.h"
#include "SDL_pixels_c.h"
#include "SDL_RLEaccel_c.h"

/* Helper functions */
/*
 * Allocate a pixel format structure and fill it according to the given info.
 */
SDL_PixelFormat *SDL_AllocFormat(int bpp,
			Uint32 Rmask, Uint32 Gmask, Uint32 Bmask, Uint32 Amask)
{
	SDL_PixelFormat *format;
	Uint32 mask;

	/* Allocate an empty pixel format structure */
	format = malloc(sizeof(*format));
	if ( format == NULL ) {
		SDL_OutOfMemory();
		return(NULL);
	}
	memset(format, 0, sizeof(*format));
	format->alpha = SDL_ALPHA_OPAQUE;

	/* Set up the format */
	format->BitsPerPixel = bpp;
	format->BytesPerPixel = (bpp+7)/8;
	switch (bpp) {
		case 1:
			/* Create the 2 color black-white palette */
			format->palette = (SDL_Palette *)malloc(
							sizeof(SDL_Palette));
			if ( format->palette == NULL ) {
				SDL_FreeFormat(format);
				SDL_OutOfMemory();
				return(NULL);
			}
			(format->palette)->ncolors = 2;
			(format->palette)->colors = (SDL_Color *)malloc(
				(format->palette)->ncolors*sizeof(SDL_Color));
			if ( (format->palette)->colors == NULL ) {
				SDL_FreeFormat(format);
				SDL_OutOfMemory();
				return(NULL);
			}
			format->palette->colors[0].r = 0xFF;
			format->palette->colors[0].g = 0xFF;
			format->palette->colors[0].b = 0xFF;
			format->palette->colors[1].r = 0x00;
			format->palette->colors[1].g = 0x00;
			format->palette->colors[1].b = 0x00;
			format->Rloss = 8;
			format->Gloss = 8;
			format->Bloss = 8;
			format->Aloss = 8;
			format->Rshift = 0;
			format->Gshift = 0;
			format->Bshift = 0;
			format->Ashift = 0;
			format->Rmask = 0;
			format->Gmask = 0;
			format->Bmask = 0;
			format->Amask = 0;
			break;

		case 4:
			/* Create the 16 color VGA palette */
			format->palette = (SDL_Palette *)malloc(
							sizeof(SDL_Palette));
			if ( format->palette == NULL ) {
				SDL_FreeFormat(format);
				SDL_OutOfMemory();
				return(NULL);
			}
			(format->palette)->ncolors = 16;
			(format->palette)->colors = (SDL_Color *)malloc(
				(format->palette)->ncolors*sizeof(SDL_Color));
			if ( (format->palette)->colors == NULL ) {
				SDL_FreeFormat(format);
				SDL_OutOfMemory();
				return(NULL);
			}
			/* Punt for now, will this ever be used? */
			memset((format->palette)->colors, 0,
				(format->palette)->ncolors*sizeof(SDL_Color));

			/* Palettized formats have no mask info */
			format->Rloss = 8;
			format->Gloss = 8;
			format->Bloss = 8;
			format->Aloss = 8;
			format->Rshift = 0;
			format->Gshift = 0;
			format->Bshift = 0;
			format->Ashift = 0;
			format->Rmask = 0;
			format->Gmask = 0;
			format->Bmask = 0;
			format->Amask = 0;
			break;

		case 8:
			/* Create an empty 256 color palette */
			format->palette = (SDL_Palette *)malloc(
							sizeof(SDL_Palette));
			if ( format->palette == NULL ) {
				SDL_FreeFormat(format);
				SDL_OutOfMemory();
				return(NULL);
			}
			(format->palette)->ncolors = 256;
			(format->palette)->colors = (SDL_Color *)malloc(
				(format->palette)->ncolors*sizeof(SDL_Color));
			if ( (format->palette)->colors == NULL ) {
				SDL_FreeFormat(format);
				SDL_OutOfMemory();
				return(NULL);
			}
			memset((format->palette)->colors, 0,
				(format->palette)->ncolors*sizeof(SDL_Color));

			/* Palettized formats have no mask info */
			format->Rloss = 8;
			format->Gloss = 8;
			format->Bloss = 8;
			format->Aloss = 8;
			format->Rshift = 0;
			format->Gshift = 0;
			format->Bshift = 0;
			format->Ashift = 0;
			format->Rmask = 0;
			format->Gmask = 0;
			format->Bmask = 0;
			format->Amask = 0;
			break;

		default:
			/* No palette, just packed pixel info */
			format->palette = NULL;
			format->Rshift = 0;
			format->Rloss = 8;
			if ( Rmask ) {
				for ( mask = Rmask; !(mask&0x01); mask >>= 1 )
					++format->Rshift;
				for ( ; (mask&0x01); mask >>= 1 )
					--format->Rloss;
			}
			format->Gshift = 0;
			format->Gloss = 8;
			if ( Gmask ) {
				for ( mask = Gmask; !(mask&0x01); mask >>= 1 )
					++format->Gshift;
				for ( ; (mask&0x01); mask >>= 1 )
					--format->Gloss;
			}
			format->Bshift = 0;
			format->Bloss = 8;
			if ( Bmask ) {
				for ( mask = Bmask; !(mask&0x01); mask >>= 1 )
					++format->Bshift;
				for ( ; (mask&0x01); mask >>= 1 )
					--format->Bloss;
			}
			format->Ashift = 0;
			format->Aloss = 8;
			if ( Amask ) {
				for ( mask = Amask; !(mask&0x01); mask >>= 1 )
					++format->Ashift;
				for ( ; (mask&0x01); mask >>= 1 )
					--format->Aloss;
			}
			format->Rmask = Rmask;
			format->Gmask = Gmask;
			format->Bmask = Bmask;
			format->Amask = Amask;
			break;
	}
	/* Calculate some standard bitmasks, if necessary 
	 * Note:  This could conflict with an alpha mask, if given.
	 */
	if ( (bpp > 8) && !format->Rmask && !format->Gmask && !format->Bmask ) {
		/* R-G-B */
		if ( bpp > 24 )
			bpp = 24;
		format->Rloss = 8-(bpp/3);
		format->Gloss = 8-(bpp/3)-(bpp%3);
		format->Bloss = 8-(bpp/3);
		format->Rshift = ((bpp/3)+(bpp%3))+(bpp/3);
		format->Gshift = (bpp/3);
		format->Bshift = 0;
		format->Rmask = ((0xFF>>format->Rloss)<<format->Rshift);
		format->Gmask = ((0xFF>>format->Gloss)<<format->Gshift);
		format->Bmask = ((0xFF>>format->Bloss)<<format->Bshift);
	}
	return(format);
}
SDL_PixelFormat *SDL_ReallocFormat(SDL_Surface *surface, int bpp,
			Uint32 Rmask, Uint32 Gmask, Uint32 Bmask, Uint32 Amask)
{
	if ( surface->format ) {
		SDL_FreeFormat(surface->format);
		SDL_FormatChanged(surface);
	}
	surface->format = SDL_AllocFormat(bpp, Rmask, Gmask, Bmask, Amask);
	return surface->format;
}

/*
 * Change any previous mappings from/to the new surface format
 */
void SDL_FormatChanged(SDL_Surface *surface)
{
	surface->format_version++;
	SDL_InvalidateMap(surface->map);
}
/*
 * Free a previously allocated format structure
 */
void SDL_FreeFormat(SDL_PixelFormat *format)
{
	if ( format ) {
		if ( format->palette ) {
			if ( format->palette->colors ) {
				free(format->palette->colors);
			}
			free(format->palette);
		}
		free(format);
	}
}
/*
 * Calculate an 8-bit (3 red, 3 green, 2 blue) dithered palette of colors
 */
void SDL_DitherColors(SDL_Color *colors, int bpp)
{
	int i;
	if(bpp != 8)
		return;		/* only 8bpp supported right now */

	for(i = 0; i < 256; i++) {
		int r, g, b;
		/* map each bit field to the full [0, 255] interval,
		   so 0 is mapped to (0, 0, 0) and 255 to (255, 255, 255) */
		r = i & 0xe0;
		r |= r >> 3 | r >> 6;
		colors[i].r = r;
		g = (i << 3) & 0xe0;
		g |= g >> 3 | g >> 6;
		colors[i].g = g;
		b = i & 0x3;
		b |= b << 2;
		b |= b << 4;
		colors[i].b = b;
	}
}
/* 
 * Calculate the pad-aligned scanline width of a surface
 */
Uint16 SDL_CalculatePitch(SDL_Surface *surface)
{
	Uint16 pitch;

	/* Surface should be 4-byte aligned for speed */
	pitch = surface->w*surface->format->BytesPerPixel;
	switch (surface->format->BitsPerPixel) {
		case 1:
			pitch = (pitch+7)/8;
			break;
		case 4:
			pitch = (pitch+1)/2;
			break;
		default:
			break;
	}