Sometimes some screens don't have good picture uniformity.
Is there anytype of software which can sort of put a filter on the outgoing image from a pc to ccancel that out?
For example there is a band which is redder this will tint that band of the screen the opposite colour of red to cancel that out.
Does this software extist or is it a pipe dream?
You can adjust the screen and image with drivers and monitor settings, but how will it know what you see on the monitor? There are optical color calibrators you can buy, but you need to adjust the colors yourself.
Correct you can't, I've never heard of a software that controls that granular of a screen position. I have worked on high-end projectors that can controls quarters of a screen, but never down to a single line of pixels. That was a $20,000 device also, not a standard desk monitor.
How will it know which part has the bad image? It just sends the same image to the monitor, you will need to tell it where the issue is. It's technically possible to have the video driver adjust each pixel (which it does anyway when it draws the screen), but you need to map out where each issue is, and tell it how to adjust. The PC can't see what you are seeing.