Flash Optimizer bug with blend modes

I ran into an interesting bug today when trying to figure out why on earth a button in our final files suddenly stopped working. In fact it was more like suddenly non-functional and only half the graphics were visible. Not cool for a button.

After a little investigating I track it down to Flash Optimizer. Apparently it does not play nice with blend modes and this button had a layer who’s blend mode was set to overlay.

Looking into it a little more I found that it’s this bug wasn’t tied to any particular optimization setting at all. Just having the file run through Flash Optimizer — even with all optimizing options unchecked– was enough to break this button that was using a blend mode.

So, moral of the story – blend modes and Flash Optimizer don’t play nice together. If you need to use optimize,r avoid blend modes.

To see the incompatibility in action, check out the SWFs below:
The button with no blend mode used
The button with blend modes

If you’re wondering this was found on Eltima Flash Optimizer version 1.48 build 1.4.8.175