kc3-lang/SDL/src

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• Hash : 89bc80f1
  Author :
  Date : 2013-08-16T06:59:19
  

  Fixed alpha blending for the MMX blit functions
  
  I see the Remarks of function SDL_BlitSurface shows that "when SDL_BLENDMODE_BLEND, we have dstA = srcA + (dstA * (1-srcA))". however, I tested some pictures but the result implies "dstA=arcA" actually. I stepped into the source code, and found after I set SDL_BLENDMODE_BLEND for the source surface, the final blit function is BlitRGBtoRGBPixelAlphaMMX when I use SDL_BlitSurface on my computer. And I found these codes:
  
      else if (alpha == amask) {
      /* opaque alpha -- copy RGB, keep dst alpha */
      *dstp = (*srcp & chanmask) | (*dstp & ~chanmask);
  
  The same code is used in BlitRGBtoRGBPixelAlphaMMX3DNOW and BlitRGBtoRGBPixelAlpha. So I think they still keep dst alpha.
  
  Best regards,
  Jianyu Guan
  

• Files

• SDL.c
• SDL_assert.c
• SDL_assert_c.h
• SDL_error.c
• SDL_error_c.h
• SDL_hints.c
• SDL_log.c
• atomic/
• audio/
• core/
• cpuinfo/
• events/
• file/
• haptic/
• joystick/
• libm/
• loadso/
• main/
• power/
• render/
• stdlib/
• test/
• thread/
• timer/
• video/

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