计算机辅助绘制黑白唐卡

Computer Assisted Rendering of Black and White Thangka

唐卡是佛教文化中一种独具特色的绘画艺术形式,构图复杂、绘制精细,黑白唐卡是其中一个独特的分支.针对手工绘制黑白唐卡物体表面的明暗渐变非常耗时耗力的问题,提出一个计算机辅助绘制黑白唐卡的系统.首先对输入的唐卡黑白线条图物体区域进行颜色标记;然后针对区域内部从一条边界向其他边界由暗变亮的物体,综合区域遮挡关系和几何特征提取线条两侧明暗特征;再针对区域内部从边界向内部由暗变亮的物体,通过距离变换或人工交互设置物体灰度控制图像;最后将明暗特征和控制图像代入泊松方程求解,得到黑白唐卡中各类物体精细明暗渐变.文中给出了黑白唐卡的绘制效果.

Thangka is a unique form of artistic paintings in Buddhism,depicting a variety of objects and including intricate details.Black and white Thangka is a special branch of Thangka,in which objects are depicted by gray gradient.Manually painting such gray gradient is highly tedious and time consuming.This paper presents a computer assisted system for rendering black and white Thangka.With different objects labelled by using ID colors in the input Thangka line drawings,our system assigns black/white feature points as boundary constraints semi-automatically for regions with gray values increasing/decreasing gradually from one side of the region to another,by taking occlusions and internal geometric features into account.It also takes grayscale images of distance field of object boundaries,or grayscale images drawn manually inside a few regions on human body,as the given brightness distribution for object regions with gray values increasing gradually from the boundaries to the interiors.Black/white feature points and grayscale images are used as constraints to solve Poisson equation to obtain gray gradient corresponding to different objects,as demonstrated by examples in the paper.