The image-editing dialogs
This dialog has two panels in which the chosen image is displayed. The right panel
displays the image the way it currently is, the left panel the is the preview
after the filters are applied. Each dialog has one or more slidebars with which
you can regulate the amount of filter applied to this image. Slide the knot to the
right for more filter, to the left for less. If you find the image has reached its
optimal state, click ok and the filters will be applied to the original image (in
the cover), this may take some time.