How to distinguish between shadows, midtones, highlights as Photoshop, to achieve color balance effect?

BradLarson / GPUImage

An open source iOS framework for GPU-based image and video processing

http://www.sunsetlakesoftware.com/2012/02/12/introducing-gpuimage-framework

BSD 3-Clause "New" or "Revised" License

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How to distinguish between shadows, midtones, highlights as Photoshop, to achieve color balance effect? #266

Open qchenqizhi opened 12 years ago

qchenqizhi commented 12 years ago

Does anyone have any good ideas?

BradLarson commented 12 years ago

There's nothing in the framework that does this right now, but I'd appreciate any contributions that add this functionality.

alariccole commented 12 years ago

I've attempted something close in my GPUImageHighlightShadowFilter. Shadows are good but the formula used to get highlights needs work. Could be a good starting point.

qchenqizhi commented 11 years ago

Thanks, I have to use another way to achieve it without OpenGL. but one day I will use GPUImage refactor it. and then I will be very happy to contribute the code.