如何混合两种RGBA颜色（像素） [英] How to blend two RGBA color (pixel)

问题描述

您好

我想混合两个32位位图，我在维基百科上找到了以下公式并创建了相应的代码，但效果不佳：

我的代码是：

 
 RGBQUAD * prgbaSrc =（RGBQUAD *）pSrcPixel; 
 RGBQUAD * prgbaDest =（RGBQUAD *）pDestPixel; 
 
 
 BYTE outAlpha = prgbaSrc-> rgbReserved + prgbaDest-> rgbReserved *（255  -  prgbaSrc-> rgbReserved）; 
 
 if（outAlpha> 0）
 {
 prgbaDest-> rgbRed =（prgbaSrc-> rgbRed * prgbaSrc-> rgbReserved / 255 + prgbaDest-> rgbRed * prgbaDest-> rgbReserved / 255 *（255  -  prgbaSrc-> rgbReserved）/ 255）/ outAlpha; 
 prgbaDest-> rgbGreen =（prgbaSrc-> rgbGreen * prgbaSrc-> rgbReserved / 255 + prgbaDest-> rgbGreen * prgbaDest-> rgbReserved / 255 *（255  -  prgbaSrc-> rgbReserved）/ 255 ）/ outAlpha; 
 prgbaDest-> rgbBlue =（prgbaSrc-> rgbBlue * prgbaSrc-> rgbReserved / 255 + prgbaDest-> rgbBlue * prgbaDest-> rgbReserved / 255 *（255  -  prgbaSrc-> rgbReserved）/ 255 ）/ outAlpha; 
} 
其他
 {
 prgbaDest-> rgbRed = 0; 
 prgbaDest-> rgbGreen = 0; 
 prgbaDest-> rgbBlue = 0; 
} 
 
 prgbaDest-> rgbReserved = outAlpha; 
 

解决方案

2016年10月20日凌晨4:36，drjackool写道：

我想要混合两个32位位图，我在维基百科上找到了以下公式并创建了相应的代码，但效果不佳：

< https://social.msdn.microsoft.com/Forums/getfile/951601 >

我的代码是：

[code]

RGBQUAD * prgbaSrc =（RGBQUAD *）pSrcPixel;

RGBQUAD * prgbaDest =（RGBQUAD *）pDestPixel; BYTE outAlpha = prgbaSrc-> rgbReserved + prgbaDest-> rgbReserved *（255 - prgbaSrc-> rgbReserved）;

公式假定alpha值归一化为[0.0,1.0]范围。你没有为[0,255]范围正确调整它们 - 你的因子是255.使它

 BYTE outAlpha = prgbaSrc-> rgbReserved + prgbaDest-> rgbReserved *（255  -  
 prgbaSrc-> rgbReserved）/ 255; 

if（outAlpha> 0）

{prgbaDest-> rgbRed =（prgbaSrc-> rgbRed * prgbaSrc-> rgbReserved / 255 + prgbaDest-> ; rgbRed * prgbaDest-> rgbReserved / 255 *（255 - prgbaSrc-> rgbReserved）/ 255）/ outAlpha;

这里也是，但是在另一个方向。设为

 prgbaDest-> rgbRed =（prgbaSrc-> rgbRed * prgbaSrc-> ; rgbReserved + 
 prgbaDest-> rgbRed * prgbaDest-> rgbReserved *（255  -  
 prgbaSrc-> rgbReserved）/ 255）/ outAlpha; 

< a name ="x_x_48c18913-32ac-4e35-b1aa-4d621aaae1db_CommunityBridge"title ="Mozilla / 5.0（Windows NT 10.0; WOW64; rv：45.0）Gecko / 20100101Thunderbird / 45.4.0通过社区论坛NNTP服务器1.1.55.0">

Hi

I want to blend two 32bit bitmaps, I found following formula on Wikipedia and create a corresponding code but not good result:

My code is:

RGBQUAD* prgbaSrc = (RGBQUAD*)pSrcPixel;
RGBQUAD* prgbaDest = (RGBQUAD*)pDestPixel;
BYTE outAlpha = prgbaSrc->rgbReserved + prgbaDest->rgbReserved * (255 - prgbaSrc->rgbReserved);
						
if (outAlpha > 0)
{
prgbaDest->rgbRed = (prgbaSrc->rgbRed * prgbaSrc->rgbReserved / 255 + prgbaDest->rgbRed * prgbaDest->rgbReserved / 255 * (255 - prgbaSrc->rgbReserved) / 255) / outAlpha;
prgbaDest->rgbGreen = (prgbaSrc->rgbGreen * prgbaSrc->rgbReserved / 255 + prgbaDest->rgbGreen * prgbaDest->rgbReserved / 255 * (255 - prgbaSrc->rgbReserved) / 255) / outAlpha;
prgbaDest->rgbBlue = (prgbaSrc->rgbBlue * prgbaSrc->rgbReserved / 255 + prgbaDest->rgbBlue * prgbaDest->rgbReserved / 255 * (255 - prgbaSrc->rgbReserved) / 255) / outAlpha;
}
else
{
	prgbaDest->rgbRed = 0;
	prgbaDest->rgbGreen = 0;
	prgbaDest->rgbBlue = 0;
}

prgbaDest->rgbReserved = outAlpha;

解决方案

On 10/20/2016 4:36 AM, drjackool wrote:

I want to blend two 32bit bitmaps, I found following formula on Wikipedia and create a corresponding code but not good result:

<https://social.msdn.microsoft.com/Forums/getfile/951601>

My code is:

[code]
RGBQUAD* prgbaSrc = (RGBQUAD*)pSrcPixel;
RGBQUAD* prgbaDest = (RGBQUAD*)pDestPixel; BYTE outAlpha = prgbaSrc->rgbReserved + prgbaDest->rgbReserved * (255 - prgbaSrc->rgbReserved);

The formula assumes that alpha values are normalized to [0.0, 1.0] range. You didn't adjust them correctly for [0, 255] range - you are off by a factor of 255. Make it

BYTE outAlpha = prgbaSrc->rgbReserved + prgbaDest->rgbReserved * (255 -
prgbaSrc->rgbReserved) / 255;

if (outAlpha > 0)
{ prgbaDest->rgbRed = (prgbaSrc->rgbRed * prgbaSrc->rgbReserved / 255 + prgbaDest->rgbRed * prgbaDest->rgbReserved / 255 * (255 - prgbaSrc->rgbReserved) / 255) / outAlpha;

And here too, but in the other direction. Make it

prgbaDest->rgbRed = (prgbaSrc->rgbRed * prgbaSrc->rgbReserved +
prgbaDest->rgbRed * prgbaDest->rgbReserved * (255 -
prgbaSrc->rgbReserved) / 255) / outAlpha;

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