magick -gamma 0 does not produce black image

[pgajdos]

The result of

magick test.png -gamma 0 -alpha off black_gamma.png

does not produce all-black image as described in https://usage.imagemagick.org/canvas/, but:

This is similar to ImageMagick/ImageMagick#1151

Tested with 7.1.1-43.

[pgajdos]

magick convert produces expected result, i. e. all-black image.

[fmw42]

I believe that there is a bug in -gamma. It is not processing the rgb channels properly on certain images. When I do.

magick logo: -transparent white logot.png

magick logot.png -gamma 0 -alpha off x.png

But the result should be totally black.

I have also tried

magick logot.png -alpha off -channel rgb -gamma 0 x.png

and

magick logot.png -alpha deactivate -gamma 0 x.png

but get the same results.

This is strange

This fails:
magick logo: -gamma 0 -alpha off y.png

and also

magick lena.png -gamma 0 -alpha off z.png

So it looks like the red channel is not processed or possibly pure red, not processed.