Scale

Allows you to change the image size relative to the starting size, expressed as a percentage of the width and height. You can scale width and height independently. To resize an image to a specific width and/or height, use the Resize transformation instead.

If you add the IMQuery transformation to a policy, use the im variable, and select Scale, you can use a query string to adjust the scale of any image using this policy. See Syntax and Examples for the syntax for the query string parameter.