Duplicate images within a collection or job

One line summary	Duplicate images within a collection (set of images) or complex object (scanned book)
Detailed description	duplicated pages in a scanned book during scanning process (job) due to operator error or machine error resulting in an incomplete final package an additional error would be missing pages, but is out of scope for this solution duplicate image files uploaded by same user or different users resulting in multiple files in digital library and confusing to the user.
Issue champion	Jodie
Possible approaches	Perceptual Image Difference utility http://pdiff.sourceforge.net/ Maurice de Rooij has created an example PHP wrapper script using the Windows binary to iterate trough files in a single directory. More about this wrapper script can be found @ Perceptual Image Diff comparison pHash - open source perceptual hash library http://www.phash.org/ NOT TESTED YET Wavelet Scalar Quantization (WSQ) http://www.cognaxon.com/index.php TOO COMPLEX TO CREATE SIMPLE PROTOTYPE Image To ASCII conversion (concept) Convert image to 8 bits per pixel which leaves 256 possible values (0-255) per pixel. If an ASCII character is assigned to each value it can be saved as a string. Using full text search one could compare this saved string to other saved strings. This approach would work well if the compared images are exactly the same and would not be usable if there is just ONE different pixel. If one is using a difference treshold this might work.
Context
AQuA Solutions	Quality assurance of a migration from TIFF to JPEG2000 Perceptual Image Diff comparison
Collections