compare, but ignore defined color pixels

[michiS]

Hi,
im looking for the command of comparing two images, but ignore the pixels of a defined color (f.e. black) from my reference pic.
So i have a reference pic. In this pic i put some parts to f.e. black or blue. At the comparison, these pixels should not be seen as different pixels (ignored).
Is there any possibility in the compare command?
compare -metric AE -subimage-search big.png reference.png result.png

Thanks, Michael

[fmw42]

I don't know if any of the metrics ignore transparent pixels, but that would be the only way that it might work.

The IM developers would have to say for sure. It would be a nice feature to add if it does not already exist.

[anthony]

I believe only the fuzz metric does as it used the same 'fuzz' factor test as color substitution.

I have not played with it much at this point though.

[michiS]

Ok thanks, but it is not really what im looking for. I think it would be a new feature. In my case it is not really easy, because most of the imagepixels have a partly transparency. I will play a bit with the fuzz factor.

[anthony]

Ok thanks, but it is not really what im looking for.

Any specific reason why not? Have you tried setting -fuzz and -metric fuzz

Any specific reason blue and black should be thought of as being equivalent?

For example could you ignore blue channel and only do compare against red and green channels.

Or is it because they are dark, or is blue irrelevant just as you want transparency to be irrelevant.

A little more information, could let us would out some pre-processing of the images to ignore these things. That is make them the same before the compare.