Possible bug -deskew auto-crop IM 6.9.5.4 Q16 Mac OSX

[fmw42]

The documentation says:

-deskew threshold{%}
straighten an image. A threshold of 40% works for most images.

Use -set option:deskew:auto-crop width to auto crop the image. The set argument is the pixel width of the image background (e.g 40).

Perhaps I am confused about what the -set option is supposed to do and what the width means (final image width or amount to trim). Nevertheless, I cannot get the -set option to work.

Base image:


Rotate by 2 deg:

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convert lena.jpg -rotate 2 lena_r2.png

Deskew no auto-crop:

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convert lena_r2.png -deskew 40% lena_r2_deskew.png

Deskew with auto-crop assuming width is amount to trim (10)

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convert lena_r2.png -set option:deskew:auto-crop 10 -deskew 40% lena_r2_deskew_ac10a.png

I also tried using -define rather than -set option (assuming there is an equivalent)

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convert lena_r2.png -define deskew:auto-crop=10 -deskew 40% lena_r2_deskew_ac10b.png

And also setting a background color (white):

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convert lena_r2.png -background white -set option:deskew:auto-crop 10 -deskew 40% lena_r2_deskew_ac10c.png

But none of the auto-crop commands worked.


P.S. If there is a -define equivalent, then please add to the -defines on the options page.

[fmw42]

Any work on confirming this issue?

[magick]

You can use -define deskew:auto-crop=10, we'll update the web page. When we used this option, here is the affine matrix it returned:

• 0.999571 -0.0292843 0.0292843 0.999571 0 0

The results look reasonable.

[fmw42]

Neither -set option or -define crop the image on my IM 6.9.5.5 Q16 Mac OSX. I get the same result as if I had not added the -set or -define.

[magick]

The documentation is wrong. The deskew:auto-crop has a value or true or false.

[fmw42]

That changes things.

But in my test, it only trims off the extra white on the north and west edges. The results still show a white border on the east (right) and south (bottom).