Why does my Minecraft look like an oil painting?

I turned down the volume on Minecraft and then set the brightness to 25% and then this happened! I thought it would have something to do with the changes i made, so i went back and put them back to how they originally were, with no improvement to my screen display. The animals are still moving, the sky still changes but I can't play like this as it changes the shape of things and confuses me, as you can see, the mountains in the background appear to be full of holes when they actually are not. I tried going on a server, refreshing mc, restarting and resetting with nothing changing each time! Please help, i really love minecraft and id hate to not be able to play! Thank you!