Fades between two 32bpp images

fade-swag-memes_v2.c

#include <stdio.h>
#include <math.h>
#include <SDL.h>
#include <SDL_image.h>

int main(int argc, char *argv[])
{
  SDL_Surface *vid = SDL_SetVideoMode(320, 240, 32, 0);
  SDL_Surface *image  = IMG_Load("pepe.png");
  SDL_Surface *image2 = IMG_Load("spurdo.png");
  image  = SDL_ConvertSurface(image, vid->format, 0);
  image2 = SDL_ConvertSurface(image2, vid->format, 0);

  if (!vid || !image)
  {
    printf("Image loading/Video setting failed, faggot. %s\n", IMG_GetError());
    return -1;
  }

  while (1)
  {
    SDL_Event ev;
    while (SDL_PollEvent(&ev))
    {
      switch(ev.type)
      {
      case SDL_QUIT:
        return 0;
      default: break;
      }
    }

    SDL_FillRect(vid, NULL, 0);

    Uint32 mul_a = (Uint16)((sinf(SDL_GetTicks() / 1000.f)+1.f) * 32767.f);
    Uint32 mul_b = mul_a ^ 0xFFFF;

    Uint32 c;
    Uint8 *dest = vid->pixels;
    Uint8 *src  = image->pixels;
    Uint8 *src2 = image2->pixels;
    int i, j;

    for (i=0; i<image->h; i++)
    {
      for (j=0; j<image->w; j++)
      {
        c = *(Uint32*)src;
        *(Uint32*)dest =
          (((((c >> 16) & 0xFF) * mul_a) & 0xFF0000)      ) | //R 1
          (((((c >> 8 ) & 0xFF) * mul_a) & 0xFF0000) >> 8 ) | //G 1
          (((((c      ) & 0xFF) * mul_a) & 0xFF0000) >> 16);  //B 1

        c = *(Uint32*)src2;
        *(Uint32*)dest +=
          (((((c >> 16) & 0xFF) * mul_b) & 0xFF0000)      ) | //R 1
          (((((c >> 8 ) & 0xFF) * mul_b) & 0xFF0000) >> 8 ) | //G 1
          (((((c      ) & 0xFF) * mul_b) & 0xFF0000) >> 16);  //B 1

        //skip color (2 bytes = 16bit)
        dest += 4;
        src += 4;
        src2 += 4;
      }

      //skip line (line width - width * color depth)
      dest += vid->pitch - (image->w * 4);
      src += image->pitch - (image->w * 4);
      src2 += image->pitch - (image->w * 4);
    }

    SDL_Flip(vid);
  }


  return 0;
}