中文摘要：

目的 目前学者已经设计了很多模拟油画、水彩、水墨等风格的非真实感绘制方法，而能够生成彩色素描的算法还不是很多。针对这一课题，在前人工作的基础上，结合线积分卷积与双色调映射技术，改进了一种彩色素描模拟方法。方法 首先基于K-means聚类对彩色图像进行分割，通过计算色彩差异性为每个区域指定两种基本色，并利用双色调映射技术计算每种颜色的密度。而后利用线积分卷积分别生成两个基本色层的素描纹理，并将两层纹理相融合来生成彩色纹理。与此同时，利用霓虹变换生成素描轮廓线。最后，将轮廓与彩色纹理相融合来得到彩色素描效果。结果 实验结果表明，本文方法能够实现由彩色图像到彩铅画的自动、实时转化。结论 本文方法从轮廓和纹理两个角度模拟了真实的彩铅绘画过程。基于K-means聚类的分割方法得到的结果能够更好地反映彩色图像的颜色分布特性。通过色彩差异性计算指定基本色的策略提高了该环节的效率，满足了实时性要求。由于粉笔、蜡笔等绘画风格的调色与彩铅画类似，本文不同颜色层上下叠加的方式可以扩展到对其他介质绘画的模拟当中。

英文摘要：

Objective Non-photorealistic rendering is a technique which is committed to generate art style works. The goal of this technique is not only to represent the authenticity of graphics but also to simulate their art features, as well as their defects. This concept was first proposed in the 1980s. After years of development, non-photorealistic rendering techniques can simulate a numerous painting styles, including oil paintings, watercolor paintings, Chinese ink paintings, pencil sketches, and cartoons. The sketch is a kind of painting which presents the light and shade of an object by lines. The color sketch is a sketch painted by a small number of color pencils. Except for the light and shade, the color sketch represents color features of an object as well. When painting a color sketch, people follow the monochrome sketch and render different regions with disparate color pencils. People usually need to blend two or more colors to obtain the desired color because the types of pencils are limited. In addition, the color mixing of sketches differs from that of oil or watercolor paintings. Typically, people mix pigments on a palette. However, when doing a color sketch, they directly draw disparate color layers on the paper. The layers of stroke for each color are superimposed and interspersed to build the target color through optical blending. This feature creates a very special kind of texture and color style for the color sketch. Although many people are fond of sketches, mastering the skill of pencil drawing is not easy for everybody. Based on previous works and characteristics of color sketch, combining the duotone color reproduction with LIC techniques, we realized an improved way of generating color sketch. Method First, we fulfilled a monochrome sketch simulation process based on LIC（line integral convolution）. On this basis, we realized a new approach for the color sketch generation based on color customization, which can automatically convert a digital image into a colored pencil drawing, by researching o