A background to sprite collision detection (pixel perfect)

It checks the collision between a sprite and an image, assuming:
the coords of the sprite and the image are 0,0 of the screen
the sprite is inside the image

The parameters are
1. sprite number
2. image number
3. the transparent color

NOT TESTED ON 16 bits SCREEN MODES

                                    ` This code was downloaded from The Game Creators
                                    ` It is reproduced here with full permission
                                    ` http://www.thegamecreators.com
                                    
                                    Function BackGround_Collision (spr , img , color)


rem asume que el sprite esta contenido en una imagen y que sus coordenadas son relativas a la
rem coordenada 0,0 (top,left) de la imagen de 32 bits
rem
rem SPR =sprite to check
rem IMG =image to check
rem Color = Transparent Color

   Colision=0
   anch = sprite width(spr)
   alto = sprite height(spr)
   posx = sprite x(spr)
   posy = sprite y(spr)

   spriteimage=254
   backimage=255

   imagesource = sprite image (spr)

   make memblock from image spriteimage,imagesource
   make memblock from image backimage,img

   ancho_imagen = memblock dword (backimage,0)
   alto_image = memblock dword (backimage,4)

   base=12

   for x=0 to anch -1
      for y=0 to alto -1

          ColorSpr= memblock dword (spriteimage,12+x*4+y*anch*4)
          ColorImage=memblock dword (backimage,12+(x+posx)*4+(y+posy)*ancho_imagen*4)

          if colorspr<>colr and colorimage<>colr then colision=1

          if colision=1

               y=alto-1
               x=anch-1

          endif

      next y
   next x

   delete memblock 255
   delete memblock 254

endfunction Colision