Images are difficult to invert using code. The images which are background to an element can be inverted somehow but actual image code is difficult to invert. Try Slimjet browser with built-in invert web page colors feature. It inverts images in background as well

I agree u block consumes a lot of memory too. I switched to slimjet web browser www.slimjet.com, which already has a built-in Ad Blocker written in native C++ code. It does’nt take up an extra process to run like any other extension and takes up no extra memory.