The offset origin is not the top left corner?

[kfitfk]

I have a PSD document which contains an image as shown below



The PSD canvas size is 425x320, and the image in the layer itself is 714x329. If the top left corner of the PSD canvas is (0, 0), then the top left corner of the layer should be (-49, -3).

I exported the layer using the following command:

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convert demo.psd[2] output.png

And here is the exported image.



Then I use the following command to crop it:

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convert output.png -crop 425x320+49+3\! cropped.png

And here is the cropped image. Notice that it is not the same area as shown in the PSD canvas.



It turns out that when cropping, the offset origin of output.png is not the top left corner corner. It is the point that matches the (0, 0) point of the PSD canvas. So if I do

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convert output.png -crop 425x320+0+0\! cropped.png

I can then get the image just like I do a "save as png" command in Photoshop.

My question is why the default offset origin of output.png is not the top left corner? Does this has something to do with my convert command? If I get an image from a third party, how do I check the default crop origin?

[Bonzo]

Does it help if you add +repage before the crop?

[kfitfk]

Does it help if you add +repage before the crop?

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convert output.png +repage -crop 425x320+0+0\! cropped.png

Yes, this works. Just checked out the documentation. This operator completely removes/resets the virtual canvas meta-data from the images.

I have another issue then. What if in this case output.png itself is smaller than my desired crop size? I still want to keep the result image 425x320.

Thanks.

[fmw42]

then you need to pad. try

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convert output.png +repage -crop 425x320+0+0\! +repage -gravity center -background black -extent 425x320 cropped.png

see http://www.imagemagick.org/Usage/crop/#extent

[kfitfk]

Thanks, fmw42. -extent works great.

Does the viewport cropping method described in this section http://www.imagemagick.org/Usage/crop/#crop_viewport only applies to gif output?

[fmw42]

Thanks, fmw42. -extent works great.

Does the viewport cropping method described in this section http://www.imagemagick.org/Usage/crop/#crop_viewport only applies to gif output?

No. Any format that saves the virtual canvas information. That would include GIF and PNG. I am not sure about TIFF. But does not include JPG.