android how to crop part of the image and replace to same posotion?

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http://stackoverflow.com – what I need to do is the partially image encryption(for example,blur part of the image), my logic is firstly cut part of the image,and blur those part image, after that put that processed part image back to same position of the original image. I use the Intent intent = new Intent("com.android.camera.action.CROP") to select a part of image to crop, the do some blur process to the cropped image, But I don't know how to put the processed image to the original image because I do not know the the coordinates of the cropped part. how can I achieve my goal?Thank! (HowTos)