Android GPU image, how to apply a filter to part of an image

Question

So I'm using https://github.com/CyberAgent/android-gpuimage and I want to achieve this (apply the filter only to a zone of the image):

Uri imageUri = ...;
mGPUImage = new GPUImage(this);
mGPUImage.setGLSurfaceView((GLSurfaceView) findViewById(R.id.surfaceView));
mGPUImage.setImage(imageUri);
sepiaFilter = new GPUImageSepiaFilter()
mGPUImage.setFilter(sepiaFilter);

is there a way to do something like:

TextureZone textureZone = new TextureZone(...);
sepiaFilter.setFilterOnlyOn(textureZone)

or do I need to go deeper and make a custom shader?

Answer 1

You have to write your custom filter with self-written fragment shader. In fragment shader, you should check for which fragment will be applied the filter.