GameMaker: Troubleshooting strange outlines on images

Strange outlines around images in GameMaker and fixing them
With the glitch (left) and without (right)

If you've ever tried to scale imagery (sprites / backgrounds) up while having texture (/pixel) interpolation turned on, you might have encountered some drawing artifacts. These normally look like the left part of above image, being either random black/white dots or a whole semi-transparent outline around the image. This article goes a bit in-depth about why these occur and how to fix them. Continue reading