See attached image. Taken from: https://webassembly.sh/?run-command=wapm%20install%20caputomarcos/rust-example@0.1.0
Also saw a similar issue while trying to upload images to the merveilles.town Mastodon server. The image would have similar diagonal lines that were all of the same maybe 2-4 colors and each about 1 pixel wide. I haven't touched JavaScript and the canvas element in a looong time, so I might be wrong, but my suspicion is that rendering images to it is what causes the issue.
