Crop portrait/landscape to square without resizing or knowing the width/height

[weavermedia]

I have portrait and landscape images of varying dimensions.

I'd like to crop them all to square, from the center, based on the shortest out of width and height.

In math terms I think of it like this: (Math.min(width, height)) x (Math.min(width,height))

For example:
500x1000 > crops to 500x500
1000x500 > crops to 500x500
500x500 > either goes unprocessed, or is cropped to 500x500

I've done a ton of reading and searching but I can't figure out how to reference the image width and height in a single-line command (Mac terminal).

I tried referencing %w and %h in -crop but can't get it to compare. I thought a ternary like this might work, but no luck:

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mogrify -gravity Center -crop "((%w>%h)?%h:%w)"x"((%w>%h)?%h:%w)"+0+0 +repage *.jpg

How do I do this in a single line?

[snibgo]

Sadly, "-crop" can't take expressions. You can use one "identify" command to find the minimum of (width, height), then crop to that dimension in each direction. Bash syntax:

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#!/bin/bash

DD=`identify -format "%[fx:min(w,h)]" rose:`

convert rose: -gravity center -crop ${DD}x${DD}+0+0 +repage out.png

[weavermedia]

Thanks again snibgo!

Is it possible to nest -identify inside a mogrify command so I can process a whole folder with a one-liner?

Or will I have to loop through all files with this bash script. No problem to do that, I just like one-liners

[snibgo]

Sorry, I don't know mogrify. You'll have to RTFM.

Nesting commands is a feature of bash, not IM. It's a shortcut that avoids variables. My commands above can be written as:

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convert rose: -gravity center -crop `identify -format "%[fx:min(w,h)]x%[fx:min(w,h)]+0+0" rose:` +repage out.png

I have to mention the filename (the built-in "rose:") twice: one for identify, and once for convert. Nesting identify within mogrify wouldn't help because identify would be run once, and the same result used for all files that mogrify processes.

[fmw42]

You can do it with viewport cropping and -distort SRT. See http://www.imagemagick.org/Usage/distor ... t_viewport.

Assume you have your images in test1 on the desktop. Create a new empty directory test2 also on the desktop, so that the output from mogrify does not overwrite you input images in test1

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cd desktop/test1
mogrify -path ../test2 -format jpg -set option:distort:viewport \
"%[fx:w>h?h:w]x%[fx:w>h?h:w]+%[fx:w>h?(w-h)/2:0]+%[fx:w>h?0:(h-w)/2]" \
-filter point -distort SRT 0 +repage *

With IM 7, you can do the same computations in -crop.