A mod has, in previous conversation said that images uploaded to this site may receive different amounts of loss in quality due to the compression that occurs on this site. I can no longer remember or find that previous conversation, but I would like to know if someone (preferrably a mod) can expand on why that happens, and more importantly if there is any way to predict which images are more likely to experience greater amounts of loss in quality (due to compression) from uploading. And in consequence, also which images are more likely to experience lesser if not almost negligible changes in quality.

One way this would be beneficial is being able to predict how an image is actually going to look like once its uploaded (which helps determine the "true" - or eventual quality of an image that you are considering to upload)....unless there is no way to know/its all just random?