Resize image, but keep proportion

[brianez21]

How can I use the command line 'convert' tool to resize an image with a maximum size and keep proportion. For example: I have a 1024x768 image ("test.jpg") that I want to make a thumbnail of ("thumb-test.jpg"). I say the thumbnail can be (at most) 320x320. The resulting image should then have the size of 320x240. And same thing if the image was 768x1024 - to result in 240x320. Thanks in advance!

[magick]

ImageMagick, by default, scales an image while maintaining the original aspect ratio of the image as you require.

[brianez21]

Could you give me an example of how I would specify that on the command line?

[magick]

See http://www.imagemagick.org/Usage/resize/ for examples on resizing an image.

[brianez21]

Thanks