sdlpixel.h

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#ifndef GCN_SDLPIXEL_HPP
#define GCN_SDLPIXEL_HPP
 
#include "SDL.h"
 
#include "guichan/color.h"
 
namespace gcn
{
 
    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);
    }
 
    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);
    }
 
    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;
    }
 
    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);
    }
 
    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