sdlpixel.h

Linux系统下的《红色警戒》游戏

/*      _______   __   __   __   ______   __   __   _______   __   __                 
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 * Copyright (c) 2004, 2005 darkbits                        Js_./
 * Per Larsson a.k.a finalman                          _RqZ{a<^_aa
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#ifndef GCN_SDLPIXEL_HPP
#define GCN_SDLPIXEL_HPP

#include "SDL.h"

#include "guichan/color.h"

namespace gcn
{

    /**
     * Checks a pixels color of an SDL_Surface.
     *
     * @param surface an SDL_Surface where to check for a pixel color.
     * @param x the x coordinate on the surface.
     * @param y the y coordinate on the surface.
     * @return a color of a pixel.
     */
    inline const Color SDLgetPixel(SDL_Surface* surface, int x, int y)
    {
        int bpp = surface->format->BytesPerPixel;

        SDL_LockSurface(surface);

        Uint8 *p = (Uint8 *)surface->pixels + y * surface->pitch + x * bpp;
    
        unsigned int color = 0;
    
        switch(bpp)
        {
          case 1:
              color = *p;
              break;
        
          case 2:
              color = *(Uint16 *)p;
              break;
        
          case 3:
              if(SDL_BYTEORDER == SDL_BIG_ENDIAN)
              {
                  color = p[0] << 16 | p[1] << 8 | p[2];
              }
              else
              {
                  color = p[0] | p[1] << 8 | p[2] << 16;
              }
              break;
        
          case 4:
              color = *(Uint32 *)p;
              break;
        
        }

        Uint8 r,g,b,a;
    
        SDL_GetRGBA(color, surface->format, &r, &g, &b, &a);
        SDL_UnlockSurface(surface);

        return Color(r,g,b,a);
    }

    /**
     * Puts a pixel on an SDL_Surface.
     *
	 * @param surface an SDL_Surface to put the pixel on
     * @param x the x coordinate on the surface.
     * @param y the y coordinate on the surface.
     * @param color the color the pixel should be in.
     */
    inline void SDLputPixel(SDL_Surface* surface, int x, int y, const Color& color)
    {
        int bpp = surface->format->BytesPerPixel;
        
        SDL_LockSurface(surface);

        Uint8 *p = (Uint8 *)surface->pixels + y * surface->pitch + x * bpp;
    
        Uint32 pixel = SDL_MapRGB(surface->format, color.r, color.g, color.b);

        switch(bpp)
        {
          case 1:
              *p = pixel;
              break;
        
          case 2:
              *(Uint16 *)p = pixel;
              break;
        
          case 3:
              if(SDL_BYTEORDER == SDL_BIG_ENDIAN)
              {
                  p[0] = (pixel >> 16) & 0xff;
                  p[1] = (pixel >> 8) & 0xff;
                  p[2] = pixel & 0xff;
              }
              else
              {
                  p[0] = pixel & 0xff;
                  p[1] = (pixel >> 8) & 0xff;
                  p[2] = (pixel >> 16) & 0xff;
              }
              break;
        
          case 4:
              *(Uint32 *)p = pixel;
              break;
        }
    
        SDL_UnlockSurface(surface);
    }

    /**
     * Blends two 16 bit colors together.
     *
     * @param src the source color.
     * @param dst the destination color.
     * @param a alpha.
     */
    inline unsigned int SDLAlpha16(unsigned int src, unsigned int dst, unsigned char a)
    {
		// Loses precision for speed
		a = (255 - a) >> 3;

		src = (((src << 16) | src) & 0x07E0F81F);
		dst = ((dst << 16) | dst) & 0x07E0F81F;
		dst = ((((dst - src) * a) >> 5) + src) & 0x07E0F81F;
		return (dst >> 16) | dst;
    }
    
    /**
     * Blends two 32 bit colors together.
     *
     * @param src the source color.
     * @param dst the destination color.
     * @param a alpha.
     */
    inline unsigned int SDLAlpha32(unsigned int src, unsigned int dst, unsigned char a)
    {
		a = 255 - a;

		unsigned int src2 = (src & 0xFF00FF00) >> 8;
		src &= 0x00FF00FF;

		unsigned int dst2 = (dst & 0xFF00FF00) >> 8;
		dst &= 0x00FF00FF;

		dst = ((((dst - src) * a) >> 8) + src) & 0x00FF00FF;
		dst2 = ((((dst2 - src2) * a) >> 8) + src2) & 0x00FF00FF;
		return dst | (dst2 << 8);
    }
    
    /**
     * Puts a pixel on an SDL_Surface with alpha
     *
	 * @param surface an SDL_Surface to put the pixel on
     * @param x the x coordinate on the surface.
     * @param y the y coordinate on the surface.
     * @param color the color the pixel should be in.
     */
    inline void SDLputPixelAlpha(SDL_Surface* surface, int x, int y, const Color& color)
    {
        int bpp = surface->format->BytesPerPixel;
        
        SDL_LockSurface(surface);

        Uint8 *p = (Uint8 *)surface->pixels + y * surface->pitch + x * bpp;
    
        Uint32 pixel = SDL_MapRGB(surface->format, color.r, color.g, color.b);

        switch(bpp)
        {
          case 1:
              *p = pixel;
              break;
        
          case 2:
              *(Uint16 *)p = SDLAlpha16(pixel, *(Uint16 *)p, color.a);
              break;
        
          case 3:
              if(SDL_BYTEORDER == SDL_BIG_ENDIAN)
              {
                  p[0] = (pixel >> 16) & 0xff;
                  p[1] = (pixel >> 8) & 0xff;
                  p[2] = pixel & 0xff;
              }
              else
              {
                  p[0] = pixel & 0xff;
                  p[1] = (pixel >> 8) & 0xff;
                  p[2] = (pixel >> 16) & 0xff;
              }
              break;
        
          case 4:
              *(Uint32 *)p = SDLAlpha32(pixel, *(Uint32 *)p, color.a);
              break;
        }
    
        SDL_UnlockSurface(surface);
    }
}

#endif // end GCN_SDLPIXEL_HPP