extent turns entire image black

[sslebedev]

Hello,

I have .PNG images and I want to extend their size by several transparent pixels (transparent border, for example). I'm doing it like this:

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magick mogrify -background none -extent 1152x344 Background.png

It works for most of test images given, but several images like this https://www.dropbox.com/s/731r58oh5ncnb ... d.png?dl=0 becomes all black. I can add transparency to the image by '-transparent white' but it is also lost after subsequent extension. I also tryed other options, option orders etc, but it changed nothing.

What am I doing wrong? Why it bahaves like this? Can it be performed without any losses of quality?

[fmw42]

This seems to be an oddity of IM 7. Try adding -alpha set after reading the input.

In IM 6.9.6.2, this works fine

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convert Background.png -background none -extent 1152x344 tmp.png

In IM 7, this produces an all transparent image.

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magick Background.png -background none -extent 1152x344 tmp.png

But this works fine in IM 7

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magick Background.png -alpha set -background none -extent 1152x344 tmp.png

So does this:

Code: Select all

magick mogrify -alpha set -background none -extent 1200x400 background.png

[sslebedev]

Sure, it works, thank you very much.

P.S. I've been sure I tried this combination... (sad)

[magick]

Thanks for the problem report. We can reproduce it and will have a patch to fix it in GIT master branch @ https://github.com/ImageMagick/ImageMagick later today. The patch will be available in the beta releases of ImageMagick @ http://www.imagemagick.org/download/beta/ by sometime tomorrow.