I am learning how to use python's pillow library to produce images, and for a test I made it produce a 256*256 RGB image with each pixels green value equal to its x position and its blue value equal to its y position (relative to the top left corner) Everything worked fine, I got an image with green and blue gradients, just as expected, however their seems to be a solid-ish blue line from the upper left to the lower middle. This color artifact made me intrigued. I checked that my program worked correctly, which it did. I don't know if It's my computer monitor, or some visual effect, but I'm puzzled as to why I am seeing this? Could you shed some light on this? The image is attached.