Corrupted RGBA Channels when decoding images.

When I try and decode an encoded image from another file something weird happens.

Some of the color channels get swapped.

For example, if I encode `bee.png` into `apple-test.png` and save as `output.png`
I get the following image:


If I decode the resulting image with `stego decode image -i output.png`, I get the following corrupted image:


Seems like the Blue and Green color channels are being swapped.

Running the decoding loop in reverse doesn't fix the problem.