Color sketch generation

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Abstract
In this paper, we introduce an NPR system to generate color sketches in a free-hand drawing style. From observation, we found out that in a free-hand style both shape and color of image regions are stylized, which contributes cooperatively to the visual effect of a sketch. With the color regions obtained by our interactive segmentation algorithm, we create a stylized color sketch in two steps. First, in order to manifest the lighting and shading of each region, we shrink the boundary,of the color regions with a luminance-based algorithm emphasizing the highlight parts, which enforces consistency with the free-hand artist style of the sketch. Second, the proposed color shift algorithm is applied to image regions to emphasize the main content of the sketch and acquires a visually pleasing combination,of color. We choose the optimal combination,by minimizing the energy function based on an artist drawn color database, artistic drawing rules and input image colors. The generated results show that our system can produce aesthetically pleasing sketches. Keywords: non-photorealistic rendering, boundary shrinking,