Yeah, like you said they literally already wrote the code that does that, not sure why they didn't use it. Setting compression to 0 is still 2 full seconds of lag for me (down from 8s), so there's still a lot of overhead. There are faster png implementations but I think re-encoding a 2MB JPEG into a 20MB PNG (to be re-encoded back to JPG by whatever program you paste it into) is kind of missing the mark.