Blend Modes, Part II
In Part I of this series, I showed how I was able to eventually figure out how to create the Linear Burn blend mode effect and how to apply this effect to a Border element.
In Part II of this series, I am going to start off by showing how I was able to truly verify that I had written the Linear Burn blend mode effect correctly. And, then, I will share a few of the A + B = R gradient squares for a few of the blend modes that Paul Dunn’s post didn’t have. Finally, I will share the full blend mode effect library and the test harnesses that go with it.
So … here we go …
With the Linear Burn blend mode effect that I had created, it bothered me that the gradient that I had blended with the green … was white to gray … and not white to black as Robby’s post had shown. Was I doing things correctly? Was the HLSL that I written, right?
A little more searching and I ran into Paul Dunn’s post on Photoshop’s blend modes. Ah! Perfect! Exactly what I wanted, and sure enough, I had written Linear Burn correctly. Check out the screen shot below (from my test harness) and compare it to what you see on Paul Dunn’s post. A match. Whew!
At that point, I started creating and going through every blend mode in his blog post, verifying each along the way. This went along fine until I hit the Vivid Light blend mode. The math that he had just wasn’t working. I tried to figure out what was wrong with it, but eventually I ran into another post that had a different way of expressing the math … it was in HLSL! Plugging in this HLSL worked! And what’s better, he had some additional effects that could be added to the library I was creating. And, so, I finished it off.
Hard Mix Effect
Finally, Nathan’s post had a visual way of verifying things as well (near the bottom) and so I included in my test harness a window that let’s you apply the various blend mode effects to images from Nathan’s page. Here’s a screen shot of that window (with the Phoenix blend mode effect applied … which I think looks cool):
Without any further adieu, here’s the blend mode effects library and the test harness. All the same caveats apply to what you need on your machine to build the sample code (.NET 3.5 SP1, DirectX SDK, and the Shader Effects BuildTask and Templates from the WPF Futures stuff on CodePlex).
If you don’t want to build the library and test harness yourself … here are the binaries.
Also, I now have a live Silverlight test harness (you will need the Silverlight 3.0 runtime, 3.0.40624).
p.s. Thanks to Kevin Moore for the Color Picker that I used in this sample code. I believe I created that Color Picker from an article he did at one point. In fact, I think that some variant of this Color Picker ended up in his Bag-o-Tricks.