Check pixel data for alterations

[isonix]

I wonder if there is a tool in ImageMagick that is able to identify potential areas of an image that may have been modified. If not, is there a technique I can look into?

I am mostly interested in finding obvious alterations, for example in a scanned transcript where someone copy and pasted some digits to change some grades.

[snibgo]

You can easily find the pixels that have changed between two versions of an image.

But I suppose you have only one version. This is difficult. If you suspect copy-pasting of digits, you could compare appropriate crops from the image. If you find an exact match, you can be (almost) certain it has been copied.

[magick]

If you have a reference image, you can use the compare utility. If the metric is not zero, its been altered and the exact location of the change can be visually checked in the output image:

• compare -metric rmse transcript.png reference.png difference.png