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

Post any defects you find in the released or beta versions of the ImageMagick software here. Include the ImageMagick version, OS, and any command-line required to reproduce the problem. Got a patch for a bug? Post it here.
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fmw42
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Possible bug IM 6: Inconsistency in getting mean of alpha data?

Post by fmw42 » 2019-07-02T14:45:06-07:00

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

Code: Select all

magick x.png -format "%[fx:mean.o]" info:
0

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magick
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Joined: 2003-05-31T11:32:55-07:00

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

Post by magick » 2019-07-05T09:48:19-07:00

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

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