Grayscale images are causing trouble

[jonsneyers]

I think it's because your code assumes the image either has 3 channels (RGB) or 4 (RGBA), but there's also a possibility that it has just 1 channel (grayscale). When attempting to decode grayscale images, things go wrong because you're trying to access non-existent channels.

For grayscale images, you can just set R=G=B=[channel 0 value].

[hrj]

Thanks @jonsneyers for reporting. Fixed and added a sample grayscale image to the demo.