Well, you have to ask yourself - how much information remains in the image after I apply this method? Is the state of the obfuscated image still related someho

Well, you have to ask yourself - how much information remains in the image after I apply this method? Is the state of the obfuscated image still related somehow to the state of the non-obfuscated version? If yes, your obfuscation method sucks. You need to change the image in such a way that the state of the obfuscated part after you apply the method is not related in any way to its state before. Otherwise clever algorithms will always find a way to "leak" info out of your poor choice of method. The best thing is to just drop a black (#000000) blob over the relevant part, completely replacing the part snd deleting previous bits 100%. There's no information leak other than size then. Blurring algos, pixelation, all that fancy stuff from the movies looks good on screen but is naive in practice. Of course, if you use a "smart" file format that has undo history and such, then you might still be leaking info.