Compute the percentage of difference between 2 JPEG images of the same size. Alternatively, compare two bitmaps as defined in [[basic bitmap storage]].

Useful for comparing two JPEG images saved with a different compression ratios.

You can use these pictures for testing (use the full-size version of each):

{|
|-
!50% quality JPEG
!100% quality JPEG
|-
|[[Image:Lenna50.jpg|200px]]
|[[Image:Lenna100.jpg|200px]]
|-
|[http://rosettacode.org/mw/images/3/3c/Lenna50.jpg link to full size 50% image]
|[http://rosettacode.org/mw/images/b/b6/Lenna100.jpg link to full size 100% image]
|}

The expected difference for these two images is 1.62125%