WPF - 控制半透明层之间的混合

问题描述

在数字成像中，当叠加两个视觉层时，您可以通过多种方式计算当来自较低层的光以某种方式穿过阻挡层时产生的图像.这可以提供不会作为自然现象发生的效果，例如颜色相乘.

以下是 Photoshop 中提供的图层混合模式菜单的示例:

I recommend visiting the article Understanding Blending Modes if this topic isn't something you're familiar with. It provides a great showcase of the results of each option against two layers.

As far as I can tell, WPF only provides the 'Normal' option. That is, the following UI just blends colours as though they were coloured gels:

<Grid>
  <Ellipse Width="40" Height="40" Fill="#80FF0000" Margin="16,0,0,0" />
  <Ellipse Width="40" Height="40" Fill="#8000FF00" Margin="32,32,0,0" />
  <Ellipse Width="40" Height="40" Fill="#800000FF" Margin="0,32,0,0" />
</Grid>

Which looks like this:

I'd like to know if there's any way to control the way in which layers blend.

解决方案

What you are looking for is called blend modes.

Here is a simple example of how it can be achieved using pixel shaders. You would use multi-input shader effect for this.

Here is a very good complete tutorial that walks you through creating a reusable library of blend modes using a multi-input shader effect.

Blend modes as an intrinsic part of the WPF APIs have been frequently requested since early CTPs but never made it into the product.

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