src/video/sdl/sdl_renderer.cpp File Reference

#include "video/sdl/sdl_renderer.hpp"
#include "video/drawing_request.hpp"
#include "video/sdl/sdl_surface_data.hpp"
#include "video/sdl/sdl_texture.hpp"
#include <iomanip>
#include <iostream>
#include <physfs.h>
#include <sstream>
#include <stdexcept>

Go to the source code of this file.

Functions
SDL_Surface *	apply_alpha (SDL_Surface *src, float alpha_factor)

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Function Documentation

SDL_Surface* @522::apply_alpha	(	SDL_Surface *	src,
		float	alpha_factor
	)			[static]

Definition at line 31 of file sdl_renderer.cpp.

{
  // FIXME: This is really slow
  assert(src->format->Amask);
  int alpha = (int) (alpha_factor * 256);
  SDL_Surface *dst = SDL_CreateRGBSurface(src->flags, src->w, src->h, src->format->BitsPerPixel, src->format->Rmask,  src->format->Gmask, src->format->Bmask, src->format->Amask);
  int bpp = dst->format->BytesPerPixel;
  if(SDL_MUSTLOCK(src))
  {
    SDL_LockSurface(src);
  }
  if(SDL_MUSTLOCK(dst))
  {
    SDL_LockSurface(dst);
  }
  for(int y = 0;y < dst->h;y++) {
    for(int x = 0;x < dst->w;x++) {
      Uint8 *srcpixel = (Uint8 *) src->pixels + y * src->pitch + x * bpp;
      Uint8 *dstpixel = (Uint8 *) dst->pixels + y * dst->pitch + x * bpp;
      Uint32 mapped = 0;
      switch(bpp) {
        case 1:
          mapped = *srcpixel;
          break;
        case 2:
          mapped = *(Uint16 *)srcpixel;
          break;
        case 3:
#if SDL_BYTEORDER == SDL_BIG_ENDIAN
          mapped |= srcpixel[0] << 16;
          mapped |= srcpixel[1] << 8;
          mapped |= srcpixel[2] << 0;
#else
          mapped |= srcpixel[0] << 0;
          mapped |= srcpixel[1] << 8;
          mapped |= srcpixel[2] << 16;
#endif
          break;
        case 4:
          mapped = *(Uint32 *)srcpixel;
          break;
      }
      Uint8 r, g, b, a;
      SDL_GetRGBA(mapped, src->format, &r, &g, &b, &a);
      mapped = SDL_MapRGBA(dst->format, r, g, b, (a * alpha) >> 8);
      switch(bpp) {
        case 1:
          *dstpixel = mapped;
          break;
        case 2:
          *(Uint16 *)dstpixel = mapped;
          break;
        case 3:
#if SDL_BYTEORDER == SDL_BIG_ENDIAN
          dstpixel[0] = (mapped >> 16) & 0xff;
          dstpixel[1] = (mapped >> 8) & 0xff;
          dstpixel[2] = (mapped >> 0) & 0xff;
#else
          dstpixel[0] = (mapped >> 0) & 0xff;
          dstpixel[1] = (mapped >> 8) & 0xff;
          dstpixel[2] = (mapped >> 16) & 0xff;
#endif
          break;
        case 4:
          *(Uint32 *)dstpixel = mapped;
          break;
      }
    }
  }
  if(SDL_MUSTLOCK(dst))
  {
    SDL_UnlockSurface(dst);
  }
  if(SDL_MUSTLOCK(src))
  {
    SDL_UnlockSurface(src);
  }
  return dst;
}

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