User Guide

GNU Image Manipulation Program
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You can find this filter through Filters → Map → Van Gogh (LIC).
‘LIC’ stands for Line Integral Convolution, a mathematical method. The plug-in author uses mathematical terms to name his
options... This filter is used to apply a directional blur to an image, or to create textures. It could be called ‘Astigmatism’ as it
blurs certain directions in the image.
It uses a blur map. Unlike other maps, this filter doesn’t use grey levels of this blur map. Filter takes in account only gradient
direction(s). Image pixels corresponding to solid areas of the map are ignored.
15.12.12.2 Options
Figure 15.229: ‘Van Gogh (LIC)’ filter options
Tip
• To create a blur, check With Source Image. Only Filter Length slider and perhaps Integration Steps slider, are useful.
• To create a texture, check With White Noise. All sliders can be useful.
Convolution You can use two types of convolution. That’s the first parameter you have to set:
• With White Noise: White Noise is an acoustics name. It’s a noise where all frequencies have the same amplitude. Here,
this option is used to create patterns.
• With Source Image: The source image will be blurred.
Effect Image That’s the map for blur or pattern direction. This map must have the same dimensions as the original image. It
must be preferably a grayscale image. It must be present on your screen when you call filter so that you can choose it in
the drop-list.
Figure 15.230: Blurring with vertical gradient map
With a vertical gradient map, vertical lines are blurred.