possible bug -evaluate-sequence multiply

[fmw42]

IM 6.7.2.9 Q16 Mac OSX Tiger.

This is not urgent as there is an alternate way to do this with -compose multiply -flatten, but I thought I would report it anyway.

convert -size 100x100 xc:gray gray.png
convert gray.png gray.png -evaluate-sequence multiply gray2.png

I would expect the result to be at graylevel 25% (.5x.5x100) from two gray images of graylevel 50%. But the result is full white. There are no error messages of any kind, esp, about multiply not being a valid option to -evaluate-sequence

Fred

[magick]

We can reproduce the problem you posted and have a patch in ImageMagick 6.7.2-10 Beta available by sometime tomorrow. Thanks.

[anthony]

Also there is no -list EvaluateSequence to list just what methods are available to that option.

[fmw42]

Did this ever get implemented? The following does not seem to finish and does not issue an error?

convert -size 100x100 xc:gray gray.png
convert gray.png gray.png -evaluate-sequence multiply gray2.png

IM 6.7.3.1 Q16 Mac OSX Tiger


When/if it gets implemented, will it multiply the existing alpha channels in the images, if using -channel rgba -alpha on?

[magick]

Curious, the command works for ImageMagick 7.0.0 but hangs in 6.7.3. We'll investigate and get a patch into 6.7.3 in the next few days.

[fmw42]

Thanks.