How can I scale all images in a folder to the same width?

Question

I want to scale all images in a given folder to the same width (but different appropriately scaled heights). How can I do this using a GUI-based or command-line tool?

For bonus points, is it possible to restrict which images are scaled based on their initial width (that is, only scale images that have a width > x and/or a width < y)?

Answer 1

This is very easy to do with imagemagick. You should be able to install it in the Software Center. I would suggest it for batch processing of images.

The batch resizing is incredibly simple (I tested it with Ubuntu 11.10). Use the following command to resize every .jpg file to 200 pixel width, keeping the aspect ratio:

$ convert '*.jpg[200x]' resized%03d.png

This is only scratching the surface of the power of imagemagick. Resizing can be tuned endlessly. For more advanced resizing you have to use the -resize option.

You can limit the resizing to shrinking:

$ convert '*.jpg[300x>]' thumb-300-%03d.png

or enlarging:

$ convert '*.jpg[300x<]' thumb-300-%03d.png

Have look at the geometry documentation to see more options.

Answer 2

Try this:

sudo apt-get install gimp-plugin-registry

Then, open up Gimp and open the Batch plugin found in Filters > Batch > Batch Process.

Select your images in the Input tab, and define the Resize operation in the surprisingly-named Resize tab.

More information can be found here.