RESIZE

An Image Magick Tute by Flo

The Resize tool at Image Magick consists of the following algorithms:

This tutorial discusses Resize, Half and Double Size, Scale, Extent, Thumbnail and the Optional Attributes. I have not yet worked with Sample and Resample.

Whenever an image is resized, its existing pixels must be either rearranged and/or removed in the case of a reduction in size, or more pixels added for enlarging. For these operations, a variety of filters have been developed. The filter chosen by Image Magick is the one best suited to the particular type of image involved. Most of the time we don't have to specify which filter to use, thank goodness.

Following are directions for using the various algorithms, indicated by the radio buttons in Resize:

Resize:

Keep the same proportions:

Input an image that is, say 200x200, click on the Resize tab, and you'll see its dimensions entered into the box.



Delete the 200x200 in the box.





Type in 300x300 and notice that the radio Resize button is red.





Click on the Resize button. The next screen will show you the enlarged image.

New width only:

Original size 425x50, new width to be 500 with the height in the same proportion as the original.





Type in 500x. Do not type in any number for the height. It is figured automatically.

New height only:

Type x200. The image will show up resized to the proper proportions.

Percentage:

Type in 80% or another percent under or over 100%. The image will be resized to the proper proportions.

Change proportions:

Image size 200x200 to 350x300:





Type into the box: 350x300! The exclamation mark ! after the numbers makes this type of resizing work right.

Here is some additional advice on Resizing along with Optimizing (reducing file size) from Jan a.k.a. jr (witchoftaylor) for gifs and jpgs