I'm working on software that allows users to upload photos (or, potentially, any image). The photos are scaled to a maximum size (to save space) and as part of that change to the image I want to copy the Exif metadata from the original image to the resized image. If I do so however at least some of the metadata will no longer reflect the resized image (e.g. dimensions). Should I also update that metadata or should I simply preserve the original data?
Are there any standards or guidelines with regard to what metadata should be modified when editing an image; what should not be modified?
For my particular circumstances, the original image will not be retained by my software (tho it may or may not by the creator).