Scanlines are a very popular effect for modern websites and are based on the lines that are often visible when an image is viewed on a television screen. This is a simple guide for creating diagonal scanlines in Inkscape 0.47.
Start by opening the Inkscape document you want to add scanlines to. Turn on the grid overlay from the view menu or by pressing the hash key. Next zoom in until you can see each pixel – a zoom level of about 3000% usually works well. Find an empty area in the document measuring 6x6 pixels.
Using the rectangle tool create the following temporary pattern. Select the image and convert it to a pattern by going to "Object->Pattern->Objects to Pattern" or by pressing "Alt+I". You can now delete the temporary pattern.
Zoom back out and turn the grid overlay back off. You can now use the scanline pattern as a fill for any suitable shape. Select the shape, open the "Fill and Stroke" panel ("Ctrl+Shift+F") and choose Pattern as the Fill option. Select the scanline pattern from the drop down list.
You can tweak the opacity setting or the colour of the pattern to obtain a range of effects. This is just one example of how your scanlines may look.