Sharpening increases the contrast of pixels around the edges of objects to increase the images definition or sharpness.
The Sharpen dialog box is displayed.
As you adjust the sharpness of the image using the Sharpness dialog box, you can preview the change to the image.
You can only undo the effect of the Sharpen command (and revert to the original image file) prior to saving the page containing the image. Once you save the page, the changes made to the image are permanently saved.