I learned from this thread that the redesigned MusicBrainz will use mozjpeg to reduce image size. (Cool!) If the matter has not already been decided, is this an appropriate place to discuss best practices for retaining/removing image metadata?
Like some of you, I already use tools to reduce image file size before I upload to the CAA: mozjpeg for JPEG files, and ZopfliPNG for PNG files. Such tools are called “lossless” because they can reduce file size without resampling the image or degrading image quality. But, it is possible to change the appearance of the image accidentally by removing colour correction metadata. In fact, this is the default behaviour for ZopfliPNG.
Maybe we can all agree that it’s a best practice to retain colour space metadata (such as colour profiles and gamma correction), and to remove geo tags. Meanwhile, some JPEG markers, text chunks in PNG files, and EXIF tags are more of a grey area. Text fields may contain information that’s useful for digital forensics, or that’s just funny or interesting. But, they might contain personally identifying information. (This is hypothetical, so maybe I’m worrying about nothing.)
If we can agree on some best practices, maybe we can all use the same command settings when pre-processing image uploads, and maybe those settings could even be built into the redesigned MB.