Transparency Issue with All Filters

[kerbelda]

Hi, very excited to use the framework but I'm running into an issue. I'm using AVPortraitEffectsMatte to generate a "cutout" of a picture. It uses the CIFilter below

Then I apply a filter like such:

The cutout works great but when I go to add a simple filter like Brightness, the background no longer stays transparent, as seen with the images below. I've tried using a UIImageView as well as a RenderView.

Before:

After:

Is there anything I can do on either end (masking or adding filters) to keep that transparency? I'm planning to do some real time filtering as well as one time outputs. Edit: This also happens with any PNG photo that has a transparency.

[deshan]

https://github.com/BradLarson/GPUImage2/issues/298#issuecomment-488699644