Sankaku Channel/lossy-lossless

Refers to an image file that is posted in a lossless image format, but contains degradation from having once been a lossy image format file. A good example would be a BMP or PNG image file full of JPEG degradation(artifacting) because it was once originally a JPEG.

Posting of such pictures is discouraged, since converting a JPEG or other lossy image format to a lossless picture format like BMP or PNG does nothing to improve picture quality and creates inconvenience by making the file pointlessly huge. Plus, there is a chance someone might take the degraded image, further degrade it by compressing it again into a JPEG file, and post it elsewhere.