Dispenser mentioned to me that our image scaling is working on non-linear sRGB colour space, which causes some less than ideal results on dark images
Background on issue:
- Gamma error in picture scaling by Eric Brasseur (Specifically mentions Wikipedia as doing it wrong; Slashdot thread)
- ImageMagick Manual: Resizing with Colorspace Correction
For image magick, it looks like this can be addressed by just adding some command line flags (which flags unfortunately vary by version). [Except possibly not jpeg as that's shrunk by libjpeg]
Its unclear if something similar can be done in vips well still using the very efficient sequential read and not creating a giant temporary file. There is a -a option to vipsthumbnail that could maybe be used.
(If it can only be on image magick and then not for jpeg, we possibly wouldn't want to do it at all to keep things consistent. Requires more investigation anyhow)