雖然已經有許多參數濾波器可以成功地萃取出準確且連續的線條，但是線條萃取的結果對於參數的調整十分敏感，時常導致過多的線條或是不足夠的線條。
我們提出了一個以描繪為基礎的系統，針對各種以線條組成的圖像，系統即根據使用者描繪的特定筆劃來引導出不同的抽象化線條。
在使用此系統時，使用者僅需大略地描繪物體輪廓，或是以線條塗鴉的方式標識出感興趣的區域，即可得到連貫或是結構相似的的抽象化線條。
我們針對此系統測試了各種以線條組成的圖像，實驗結果顯示此系統可以準確地萃取出理想的抽象化線條，其品質亦優於先前的技術。

While many parametric filters have successfully extracted accurate and
coherent lines, their results are sensitive to parameters tuning, leading to
either excessive or insufficient amount of lines. In this work, we present a
sketch-based system to guide the line abstraction of arbitrary images using
the user specified strokes. With the assistance of our system, the user simply
has to provide a few intuitive strokes, including tracing roughly along
the edges and scribbling on the regions of interest. The system then automatically
extracts from a detailed line abstraction those lines that are long,
coherent, and share similar structures in texture to conform the user’s intention.
We have tested our system on a wide variety of images. The experimental
results show that our system can generate concise line drawings and
outperforms state-of-the-art techniques in terms of quality and efficiency.

摘要 i
Abstract ii
Contents iii
List of Figures iv
List of Tables v
1 Introduction 1
2 Related Works 4
3 Overview 6
4 Algorithm 8
4.1 Matching for Coherence Strokes . . . 8
4.2 Matching for Neighbor Strokes . . . 14
4.3 Matching for Structure Strokes . . . 17
5 Results and Evaluation 20
5.1 Results . . . 20
5.2 Evaluation . . . 21
6 Conclusion 27
A Results 28
B User Study 30
Bibliography 37

[1] John Canny. A computational approach to edge detection. Pattern Analysis and
Machine Intelligence, IEEE Transactions on, (6):679–698, 1986.
[2] Jan Eric Kyprianidis and Jürgen Döllner. Image abstraction by structure adaptive
filtering. In Proc. EG UK Theory and Practice of Computer Graphics, pages 51–58,
2008.
[3] Holger Winnemöeller, Sven C. Olsen, and Bruce Gooch. Real-time video abstraction.
ACM Trans. Graph., 25(3):1221–1226, 2006. ISSN 0730-0301.
[4] Holger Winnemöller, Jan Eric Kyprianidis, and Sven C. Olsen. Xdog: An extended
difference-of-gaussians compendium including advanced image stylization. Computers
& Graphics, 36(6):740–753, 2012.
[5] Michael Maire, Pablo Arbeláez, Charless Fowlkes, and Jitendra Malik. Using contours
to detect and localize junctions in natural images. In IEEE Conference on
Computer Vision and Pattern Recognition (CVPR), 2008.
[6] Pablo Arbelaez, Michael Maire, Charless Fowlkes, and Jitendra Malik. Contour
detection and hierarchical image segmentation. IEEE Trans. Pattern Anal. Mach.
Intell., 33(5):898–916, May 2011. ISSN 0162-8828.
37
[7] Alex Limpaecher, Nicolas Feltman, Adrien Treuille, and Michael Cohen. Real-time
drawing assistance through crowdsourcing. ACM Transactions on Graphics (TOG),
32(4):54, 2013.
[8] Qingkun Su, Wing Ho Andy Li, Jue Wang, and Hongbo Fu. Ez-sketching: Threelevel
optimization for error-tolerant image tracing. ACM Trans. Graph (Proceedings
of SIGGRAPH 2014), 33:4, 2014.
[9] Michael Gleicher. Image snapping. In Proceedings of the 22nd annual conference
on Computer graphics and interactive techniques, pages 183–190. ACM, 1995.
[10] Yin Li, Jian Sun, Chi-Keung Tang, and Heung-Yeung Shum. Lazy snapping. ACM
Transactions on Graphics (ToG), 23(3):303–308, 2004.
[11] Yong Jae Lee, C Lawrence Zitnick, and Michael F Cohen. Shadowdraw: real-time
user guidance for freehand drawing. ACM Transactions on Graphics (TOG), 30(4):
27, 2011.
[12] Emmanuel Iarussi, Adrien Bousseau, Theophanis Tsandilas, et al. The drawing
assistant: automated drawing guidance and feedback from photographs. In ACM
Symposium on User Interface Software and Technology (UIST), 2013.
[13] Daniel Dixon, Manoj Prasad, and Tracy Hammond. icandraw: using sketch recognition
and corrective feedback to assist a user in drawing human faces. In Proceedings
of the SIGCHI Conference on Human Factors in Computing Systems, pages 897–
906. ACM, 2010.
[14] Jingwan Lu, Connelly Barnes, Stephen DiVerdi, and Adam Finkelstein. Realbrush:
Painting with examples of physical media. ACM Transactions on Graphics (TOG),
32(4):117, 2013.
[15] Itamar Berger, Ariel Shamir, Moshe Mahler, Elizabeth Carter, and Jessica Hodgins.
Style and abstraction in portrait sketching. ACM Transactions on Graphics (TOG),
32(4):55, 2013.
[16] Shulin Yang, Jue Wang, and Linda Shapiro. Supervised semantic gradient extraction
using linear-time optimization. In Computer Vision and Pattern Recognition
(CVPR), 2013 IEEE Conference on, pages 2826–2833. IEEE, 2013.
[17] Jacob O Wobbrock, Andrew D Wilson, and Yang Li. Gestures without libraries,
toolkits or training: a $1 recognizer for user interface prototypes. In Proceedings of
the 20th annual ACM symposium on User interface software and technology, pages
159–168. ACM, 2007.
[18] Gunay Orbay and Levent Burak Kara. Beautification of design sketches using
trainable stroke clustering and curve fitting. Visualization and Computer Graphics,
IEEE Transactions on, 17(5):694–708, 2011.
[19] Robert W Floyd. Algorithm 97: shortest path. Communications of the ACM, 5(6):
345, 1962.
[20] R. McDonald and K J Smith. Cie94-a new colour-difference formula*. Journal of
the Society of Dyers and Colourists, 111(12):376–379, 1995. ISSN 1478-4408.