Visual diff. The operation of finding differences between two files
by {eyeball search}. The term optical diff has also been reported,
and is sometimes more specifically used for the act of superimposing
two nearly identical printouts on one another and holding them up to
a light to spot differences. Though this method is poor for detecting
omissions in the `rear' file, it can also be used with printouts of
graphics, a claim few if any diff programs can make. See {diff}.
An interesting variant of the vdiff technique usable by anyone who
has sufficient control over the parallax of their eyeballs (e.g.
those who can easily view random-dot stereograms), is to hold up two
paper printouts and go cross-eyed to superimpose them. This invokes
deep, fast, built-in image comparison wetware (the same machinery
responsible for depth perception) and differences stand out almost
immediately. This technique is good for finding edits in graphical
images, or for comparing an image with a compressed version to spot
artifacts.
[glossary]
[Reference(s) to this entry by made by: {diff}{eyeball search}{optical diff}{vgrep}]