粉蠟筆繪圖模擬中筆觸粗細與疏密之引用與相關呈現處理

Abstract

本論文提出一個新的粉蠟筆繪圖模擬方法，探討如何利用顏色分層後的面積資訊來定義圖像中筆觸的粗細與疏密變化。進而呈現真實粉蠟筆繪圖時，筆觸來回描繪的風格。基本上吾人以畫家手繪畫圖時的習慣方式切入，目的在於模擬較真實的下筆經過，使結果貼近真實情況。做法主要如下： 1.將輸入圖像依照顏色進行分層簡化，共分為432種。 2.依照梯度方向的計算結果來決定各筆觸下筆時的參考方向。 3.根據顏色與方向資訊分出大中小區域，並產生各區使用的筆觸軌跡。 4.合併不同大小區域的筆觸軌跡，並使用不同粗細與疏密筆觸繪畫。 經本論文提出方法所處理的圖片，其結果圖的模擬效果有粉蠟筆描繪時的線條感與來回重複繪畫時的塗抹風格感受。

In pastel drawing simulation, the handling of pastel stokes of various lengths, orientations and colors are essential. In this thesis, two more issues are taken into account in the hope of adding more human-drawing flavor to the pastel drawing conversion, namely to apply pastel strokes of appropriate width and spacing onto adequate regions in the drawing. An automated system has been implemented and put into work, of which the process consists of four major stages:

Classification of the HSV color space into a 432 color palette, in addition to the classification of gradient space into 8 major orientations. An initial image segmentation into units of 3×3 pixel is conducted and in each of the 3×3 regular segment unit, representative color-index and reference direction of stroke-path are established. Regular segments are grouped into large units according to color information; depending on the number of regular segments, each of the larger units is classified as large, medium and small regions. For each region in the three-sized class, corresponding stroke-path, stroke-width and spacing are assigned. Rendering of pastel strokes in each region is performed alone every stroke-path accordingly, with some final touch for enhancing the flavor of hand-drawing.

The final outcome of the conversion in many cases demonstrates enhance visual effect, namely back-and-forth, wide-and-sparse line patterns while drawing large region of low color-contrast and thus more flavor of hand-drawing, as compared to a previous pastel-drawing simulation system.