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Is it possible to composite green screen images -- an animated actor against a green background, with a backdrop photo and make a video of that using avassetwriter on the iPhone.

I have an application that creates a sequence of screenshots of an animated character against a green background. I'd like to composite those with a photograph from their library.

Is there some way to composite the two into a video on the iPhone?

Thanks,

techdog
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1 Answers1

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Yes, there is. I just added a chroma key filter to my GPUImage framework, which should let you do realtime green screen effects from camera, image, or movie sources. You just need to use a GPUImageChromaKeyBlendFilter, set the color you want to replace in the first image or video source, set the sensitivity threshold, and optionally set the amount of smoothing to use on colors that are not quite matches of your target.

It acts like the other blend filters in the framework, where you supply the video source to filter as the first input to the filter, and the image or video to replace you target color with as the second input.

I haven't yet tuned this particular filter for performance, but you should easily be able to get 30 FPS processing for 640x480 frames on an older iPhone 4 (~15-20 FPS for 720p).

Brad Larson
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