[RESOLVED] Suggestion For Enhancement

[fmw42]

For reference see the difference processing at viewtopic.php?f=1&t=29823

The idea is to add a new define or threshold argument to compare so that the (red) overlay of where there are differences (in the first output) is thresholded first so as to remove some of the very small differences from the overlay. (No change to the correlation image).

This is not a very high priority for me. Just a nice additional feature to match the kind of processing the OP's js reference is doing, so as to save all the extra additional -compose difference post-processing.

[snibgo]

Isn't this already provided by "-fuzz"?

For example:

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convert rose: -evaluate pow 0.9 r.png

compare -metric RMSE  -subimage-search rose: r.png d0.png

compare -metric RMSE  -fuzz 1% -subimage-search rose: r.png d1.png

compare -metric RMSE  -fuzz 3% -subimage-search rose: r.png d3.png

The numbers we get out are the same (because metric RMSE isn't sensitive to fuzz), but the output images d0, d1 and d3.png are different (the numbers of red pixels decreases).

[fmw42]

Good catch, snibgo. I had not connected fuzz with that feature. The only difference is that the image gets muted (lower saturation) before the overlay is added.

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compare -metric rmse -fuzz 5% People.jpg People2.jpg people_compare4.png

But that can be fixed using the lowlight-color:

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compare -metric rmse -fuzz 5% -lowlight-color none People2.jpg people_compare5.png

Unfortunately, adding -alpha off, does not turn off the fully opaque alpha channel. I had to revert to

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compare -metric rmse -fuzz 5% -lowlight-color none People.jpg People2.jpg miff:- | convert - -alpha off people_compare6.png