You can resize a group of images by specifying their dimensions in pixels or specifying a percentage of their original size. The Resize Images tool guides you through the process.
To resize a group of images, in the photo browser, select one or more images, and then click the Batch Resize tool on the image tool panel at right.
In the Resize Images tool, select one of the following options:
Intelligent image size adjustment: Resize the images to a specific size (use the longer one comparing the width and height) in pixel.
Based on defined width or height: choose width or height and resize the images to a specific size.
User defined dimension: define both the pixel for width and height to resize. If the option of keep the constrain is checked, the images will be resized accordingly to keep the constrain.
Percentage of original: resize the image to a specific percentage of your original image pixel.
Then, you may specify some options to batch save the images and the quality and sampling parameter of the JPG files you want to save.