The Scanlines option recreates the effect of horizontal lines across an image. This effect is very popular right now, and almost gives the impression that the image is being viewed on a TV screen or computer monitor. There are no options for this effect. Simply click Save or Save As... to save the effect, or Cancel to exit without saving changes.
Note: Due to the resolution of monitors, and the way images are drawn to screen, the Scanlines option will look strange at resolutions under 100%. Click the + button as many times as it takes to zoom into 100% to see the actual scanlines. For this same reason, you may want to avoid resizing the image after adding scanlines. If you wish to both make an image smaller AND add scanlines, you will typically get better results by resizing first, and then adding scanlines second. Your experience may vary. Experiment to find out the best solution for your images.