From: "rmagick@..." <rmagick@...>
Date: 2005-09-09T03:06:29+09:00
Subject: Re: RMagick Thumbnailing Question

Sounds to me like you need a 2-step method, assuming the original
images are not already 300x100.

Use the change_geometry method to compute the new dimensions for your
thumbnail. If you want to make sure that your thumbnail is always 100
pixels high, specify a geometry string argument with just your target
height, like this: "x100". If you want your thumbnail to be always 300
pixels wide, just specify the target width: "300". The change_geometry
method will compute new dimensions you can use as arguments to the
resize method. If the result still doesn't have the right shape you can
use the crop method to crop the resized image to the shape you want. If
you want the middle 100x100 part of the image you can use something
like:

img.crop!(Magick::CenterGravity, 100, 100)