If you uploaded an image, and if your server has the Image::Magick Perl module installed, you have the additional option of creating a thumbnail of the image that you uploaded. To create a thumbnail, check the "Create a thumbnail for this image" option, then adjust the Width and Height boxes to scale the image to the size or percentage that you want. You can scale either by pixel size (Pixels in the pull-down menu), or by percentage (Percent in the pull-down menu).

In addition, you can scale width and height either in proportion to their original sizes, or out of proportion (to distort the image). By default, the Constrain proportions box is checked; this will ensure that if you make a change to either the width or height, the other dimension will be scaled appropriately. If you uncheck the Constrain proportions checkbox, you will be able to scale the width and height to different proportions.

When creating a thumbnail, the POPUP IMAGE button will generate HTML to display your thumbnail image as a link to a popup window containing the full-size image that you uploaded. The EMBEDDED IMAGE button will generate HTML to display your thumbnail image as a link to the full-size image in the same window.

See Uploading a File for more details.