Possible bug IM 6: Inconsistency in getting mean of alpha data?

[fmw42]

IM 6.9.10.51 Q16 Mac OSX

# create fully transparent image

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convert -size 100x100 xc:none x.png

Test if transparent is opposite polarity if use %[mean] than %[fx:mean]

# expected result

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convert x.png -channel a -format "%[fx:mean]" info:

0

# unexpected result

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convert x.png -channel a -format "%[mean]" info:

65535 <--- should be 0

# similarly, unexpected result

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convert x.png -format "%[fx:mean.a]" info:

1 <--- should be 0

# same if use .o rather than .a

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convert x.png -format "%[fx:mean.o]" info:

1 <--- should be 0


With IM 7.0.8.51, the following gives proper results:

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magick x.png -channel a -format "%[fx:mean]" info:

0

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magick x.png -channel a -format "%[mean]" info:

0

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magick x.png -format "%[fx:mean.a]" info:

0

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magick x.png -format "%[fx:mean.o]" info:

0

[magick]

IMv6 has deficiencies that we addressed in IMv7. This is one of them. We cannot fix the problem you posted.