I recently tried out pHash and it seemed to be a good tool for detecting nearly duplicate images. Certainly superior to calculating md5 for images and comparing

I recently tried out pHash and it seemed to be a good tool for detecting nearly duplicate images. Certainly superior to calculating md5 for images and comparing those. However, if the images have different cropping, slight rotation or different brightness/contrast setting pHash didn't seem to work well enough. I got better results with http://www.imgseek.net/ http://www.imgseek.net/ for my image set.