Legacy ImageMagick Discussions Archive

IM v6.9.2-5 on Windows 8.1.
The image has two pixels with a=0 and one pixel at a=1. So the mean should be 0.33333.

This worked fine in v6.9.1-6. Perhaps the fix to alpha minima >= maxima caused this problem.

Try

• convert xc:White xc:None xc:None +append -format '%[fx:mean.o]' info:
  0.666667

Which displays the mean opacity rather than alpha. Is that not correct?

Which displays the mean opacity rather than alpha. Is that not correct?

No, it isn't correct. We have one white pixel (alpha = opacity = 1) and two transparent black pixels (alpha = opacity = 0). (1+0+0)/3 = 0.3333.