I’ve been looking into optimizing images for the various image search engines and I’ve found 4 major points to address:
- Keywords in file images
- Keywords in ALT tags
- Keywords in caption text below image
- Image size
It seems at least Google’s image search uses image dimension to identify duplicate images, so if you’re working with an image other sites also use, it would be helpful to modify the image size by a few pixles, so as to not get filtered out as duplicate.