[SDL] truble to get the color of a surface pixel

[f]

thanks!! :)

On 7/4/06, antonmasteR <antonmaster at mail.ru> wrote:
> You can check the pixel color with this function:
>
> Uint32 GetPixel(SDL_Surface *surf, int x, int y)
> {
>         //This function returns pixels color
>         int bpp = surf->format->BytesPerPixel;
>         Uint8 *p = (Uint8 *)surf->pixels + y * surf->pitch + x * bpp;
>
>         switch (bpp)
>         {
>                 case 1:
>                         return *p;
>
>                 case 2:
>                         return *(Uint16 *)p;
>
>                 case 3:
>                         if (SDL_BYTEORDER == SDL_BIG_ENDIAN)
>                                 return p[0] << 16 | p[1] << 8 | p[2];
>                         else
>                                 return p[0] | p[1] << 8 | p[2] << 16;
>
>                 case 4:
>                         return *(Uint32 *)p;
>
>                 default:
>                         return 0;
>         }
> }
>
> then use SDL_GetRGB to convert the Uint32 color value into pixel rgb format.
>
>
> ---
> http://gamescreators.sf.net      Linux game developing community
>
> -----Original Message-----
> From: f <ferranf at gmail.com>
> To: sdl at libsdl.org
> Date: Mon, 3 Jul 2006 21:06:34 +0200
> Subject: [SDL] truble to get the color of a surface pixel
>
> >
> > i need to get the color of a pixel of specific position of a surface,
> > i'm trying something like this:
> >
> >
> > int frogoutofbounds(SDL_Surface *maskbackground)
> > {
> >         SDL_Color col;
> >         Uint32 pixupleft;
> >         SDL_PixelFormat *fmt;
> >         Uint8 r,g,b;
> >         pixupleft=frog.pos.x+(frog.pos.y*800);
> >         fmt=maskbackground->format;
> >         SDL_GetRGB(pixupleft,fmt,&r,&g,&b);
> >         col.g=g;
> >         printf("green color:%d\n",col.g);
> > ......
> >
> >
> > but this don't return me the rgb code, it returns me an non-sense
> > number that isn't correct.
> >
> > frog is a global struct that have the position of a sprite (frog.pos)
> > , i want to know if the upper left corner of the sprite  (800x600
> > screen size) is over the "black zone" of the mask of the background.
> >
> > thanks in advance
> >
> >
> > --
> > f || www.ct.upc.edu/%7eferran
> >
> > _______________________________________________
> > SDL mailing list
> > SDL at libsdl.org
> > http://www.libsdl.org/mailman/listinfo/sdl
> >
>
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-- 
f || www.ct.upc.edu/%7eferran