alphablendfunc.cpp

对代数公式进行算法优化 可以节省大量计算时间 希望大家喜欢

#include "stdafx.h"
#include "alphablendfunc.h"

extern "C" inline UINT UnoptimizedAlphablend( UINT dest, UINT source, BYTE nAlpha)
{
	if( 0 == nAlpha )
		return dest;

	if( 255 == nAlpha )
		return source;

	BYTE nInvAlpha = 255-nAlpha;

	BYTE nSrcRed   = (source & 0xff0000) >> 16; 
	BYTE nSrcGreen = (source & 0xff00) >> 8; 
	BYTE nSrcBlue  = (source & 0xff); 

	BYTE nDestRed   = (dest & 0xff0000) >> 16; 
	BYTE nDestGreen = (dest & 0xff00) >> 8; 
	BYTE nDestBlue  = (dest & 0xff); 

	BYTE nRed  = (BYTE)(nSrcRed   * (nAlpha/255.0f)) + (BYTE)(nDestRed * (nInvAlpha/255.0f));
	BYTE nGreen= (BYTE)(nSrcGreen * (nAlpha/255.0f)) + (BYTE)(nDestGreen * (nInvAlpha/255.0f));
	BYTE nBlue = (BYTE)(nSrcBlue  * (nAlpha/255.0f)) + (BYTE)(nDestBlue * (nInvAlpha/255.0f));
	
	return 0xff000000 | nRed << 16 | nGreen << 8 | nBlue;
}


extern "C" inline UINT OptimizedAlphablend( UINT dest, UINT source, BYTE nAlpha)
{
	if( 0 == nAlpha )
		return dest;

	if( 255 == nAlpha )
		return source;

	BYTE nInvAlpha = 255-nAlpha;

	BYTE nSrcRed   = (source & 0xff0000) >> 16; 
	BYTE nSrcGreen = (source & 0xff00) >> 8; 
	BYTE nSrcBlue  = (source & 0xff); 

	BYTE nDestRed   = (dest & 0xff0000) >> 16; 
	BYTE nDestGreen = (dest & 0xff00) >> 8; 
	BYTE nDestBlue  = (dest & 0xff); 

	BYTE nRed  = ( nSrcRed   * nAlpha + nDestRed * nInvAlpha   )/255;
	BYTE nGreen= ( nSrcGreen * nAlpha + nDestGreen * nInvAlpha )/255;
	BYTE nBlue = ( nSrcBlue  * nAlpha + nDestBlue * nInvAlpha  )/255;
	
	return 0xff000000 | nRed << 16 | nGreen << 8 | nBlue;
}


extern "C" inline UINT VeryOptimizedAlphablend( UINT dest, UINT source, BYTE nAlpha)
{
	if( 0 == nAlpha )
		return dest;

	if( 255 == nAlpha )
		return source;

	BYTE nInvAlpha = 255-nAlpha;

	BYTE nSrcRed   = (source & 0xff0000) >> 16; 
	BYTE nSrcGreen = (source & 0xff00) >> 8; 
	BYTE nSrcBlue  = (source & 0xff); 

	BYTE nDestRed   = (dest & 0xff0000) >> 16; 
	BYTE nDestGreen = (dest & 0xff00) >> 8; 
	BYTE nDestBlue  = (dest & 0xff); 

	BYTE nRed  = ( nSrcRed   * nAlpha + nDestRed * nInvAlpha   )>>8;
	BYTE nGreen= ( nSrcGreen * nAlpha + nDestGreen * nInvAlpha )>>8;
	BYTE nBlue = ( nSrcBlue  * nAlpha + nDestBlue * nInvAlpha  )>>8;
	
	return 0xff000000 | nRed << 16 | nGreen << 8 | nBlue;
}