Enhanced LIC pencil filter

This paper proposes an extension to the existing automatic pencil drawing generation technique based on line integral convolution (LIC). The original LIC pencil filter utilizes image segmentation and texture direction detection techniques for defining outlines and stroke directions, and the quality of a resulting image depends largely on the result of image segmentation. It may fail to generate a reasonable result when the segmentation result is not consistent with the structure of the input image. To solve this problem, we propose in this paper to avoid the explicit region subdivision. Instead, we divide a source image into layers of successive intensity ranges, generate a stroke image for each layer, and add them together to obtain the final pencil drawing.