转换ARBG到RGB与alpha混合 [英] Converting ARBG to RGB with alpha blending

问题描述

让我们说，我们有一个ARGB颜色：

Let's say that we have an ARGB color:

Color argb = Color.FromARGB(127, 69, 12, 255); //Light Urple.

在此画在现有颜色的顶部，颜色和谐。因此，当它与白色混合，产生的颜色是 Col​​or.FromARGB（255，162，133，255）;

When this is painted on top of an existing color, the colors will blend. So when it is blended with white, the resulting color is Color.FromARGB(255, 162, 133, 255);

该解决方案应该像这样工作：

The solution should work like this:

Color blend = Color.White; 
Color argb = Color.FromARGB(127, 69, 12, 255); //Light Urple.      
Color rgb = ToRGB(argb, blend); //Same as Color.FromARGB(255, 162, 133, 255);

什么是 ToRGB 的实施？

推荐答案

这就是所谓的 alpha混合< /a>.

It's called alpha blending.

In伪码，假设背景色（混合）总是有255阿尔法。还假定alpha为0-255。

In psuedocode, assuming the background color (blend) always has 255 alpha. Also assumes alpha is 0-255.

alpha=argb.alpha()
r = (alpha/255)*argb.r() + (1 - alpha/255)*blend.r()
g = (alpha/255)*argb.g() + (1 - alpha/255)*blend.g()
b = (alpha/255)*argb.b() + (1 - alpha/255)*blend.b()

的注：您可能需要有点（更多）小心浮点/ INT数学和四舍五入问题，这取决于语言。铸造中间体因此的

编辑补充：

如果你没有255的阿尔法背景颜色，得到代数很多更加复杂。我以前做过，这是一个有趣的练习留给读者（如果你真的需要知道，问另一个问题:)。

If you don't have a background color with an alpha of 255, the algebra gets alot more complicated. I've done it before and it's a fun exercise left to the reader (if you really need to know, ask another question :).

换句话说，什么颜色为c融入一些背景相同的调合，再混合B.这是有点像计算A + B（这是不一样的B + A）。

In other words, what color C blends into some background the same as blending A, then blending B. This is sort of like calculating A+B (which isn't the same as B+A).

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