在非相片質感繪圖的研究中，如何讓使用者可以畫出如畫家般有技巧的線段，能夠兼顧影像特徵與抽象化，一直是很困難的問題。現行的幾種抽象化演算法都需要調整各項參數，產生不同的細節以適應不同的影像，這和畫家創作概念不相同，一般使用者也會覺得不直覺。
在本研究中，提出了一個輔助繪圖系統，可以讓使用者引導進行影像的線段抽象化，讓沒有畫畫經驗的使用者也可以快速畫出有風格的圖像。本研究基於Winnemöller, Kyprianidis和Kang等人所提出延伸型高斯差演算法進行邊緣偵測，進行有粗細的線段向量化構成的線段資料庫。當使用者繪圖的時候，進行資料庫線段比對，即時顯示於畫布之上。如此一來使用者不需要調整任何參數，就可以引導系統速寫作畫。

How to let user draw as an artist is always a difficult problem in Non-Photorealistic Rendering field. Several researches on image abstraction had proposed many algorithms, but most of them need to provide different parameters with respect to different images. In this study, we present a system that let the user join the creation of painting just like the artists do in real world.
There are four stages in our system. First two stages are preprocessing and the other two are interactive processing. In the first stage, we apply Different-of-Gaussian (DoG) filter to source image. Then vectorize the image as the associated internal representation. Different DoG results with different parameters were used to build a database for further reference. In the third stage, we calculate matching weight from database when the strokes user drew. And in the final stage, the closest edges from the database were extracted and put into the final canvas.
Our system is very intuitive and easy to use for novice user. User can draw stylish painting with a few strokes in short time.

[Curtis et al. 1997]
Curtis, C. J., Anderson, S. E., Seims, J. E., Fleischer, K. W., & Salesin, D. H. (1997, August). Computer-generated watercolor. In Proceedings of the 24th annual conference on Computer graphics and interactive techniques(pp. 421-430). ACM Press/Addison-Wesley Publishing Co..

[Salisbury et al. 1997]
Salisbury, M. P., Wong, M. T., Hughes, J. F., & Salesin, D. H. (1997, August). Orientable textures for image-based pen-and-ink illustration. InProceedings of the 24th annual conference on Computer graphics and interactive techniques (pp. 401-406). ACM Press/Addison-Wesley Publishing Co..

[Lu et al. 2012]
Lu, C., Xu, L., & Jia, J. (2012, June). Combining sketch and tone for pencil drawing production. In Proceedings of the Symposium on Non-Photorealistic Animation and Rendering (pp. 65-73). Eurographics Association.

[DeCarlo et al. 2002]
DeCarlo, D., & Santella, A. (2002, July). Stylization and abstraction of photographs. In ACM Transactions on Graphics (TOG) (Vol. 21, No. 3, pp. 769-776). ACM.

[DeCarlo et al. 2003]
DeCarlo, D., Finkelstein, A., Rusinkiewicz, S., & Santella, A. (2003, July). Suggestive contours for conveying shape. In ACM Transactions on Graphics (TOG) (Vol. 22, No. 3, pp. 848-855). ACM.

[Eisemann et al. 2008]
Eisemann, E., Winnemöller, H., Hart, J. C., & Salesin, D. (2008, June). Stylized vector art from 3d models with region support. In Computer Graphics Forum (Vol. 27, No. 4, pp. 1199-1207). Blackwell Publishing Ltd.

[Wang et al. 2004]
Wang, J., Xu, Y., Shum, H. Y., & Cohen, M. F. (2004, August). Video tooning. In ACM Transactions on Graphics (ToG) (Vol. 23, No. 3, pp. 574-583). ACM.

[Wen et al. 2006]
Wen, F., Luan, Q., Liang, L., Xu, Y. Q., & Shum, H. Y. (2006, June). Color sketch generation. In Proceedings of the 4th international symposium on Non-photorealistic animation and rendering (pp. 47-54). ACM.

[Kang et al. 2005]
Kang, H. W., He, W., Chui, C. K., & Chakraborty, U. K. (2005). Interactive sketch generation. The Visual Computer, 21(8-10), 821-830.

[Rother et al. 2004]
Rother, C., Kolmogorov, V., & Blake, A. (2004, August). Grabcut: Interactive foreground extraction using iterated graph cuts. In ACM Transactions on Graphics (TOG) (Vol. 23, No. 3, pp. 309-314). ACM.

[Berger et al. 2013]
Berger, I., Shamir, A., Mahler, M., Carter, E., & Hodgins, J. (2013). Style and abstraction in portrait sketching. ACM Transactions on Graphics (TOG),32(4), 55.

[Cootes et al. 1995]
Cootes, T. F., Taylor, C. J., Cooper, D. H., & Graham, J. (1995). Active shape models-their training and application. Computer vision and image understanding, 61(1), 38-59.

[Lee et al. 2011]
Lee, Y. J., Zitnick, C. L., & Cohen, M. F. (2011, August). ShadowDraw: real-time user guidance for freehand drawing. In ACM Transactions on Graphics (TOG) (Vol. 30, No. 4, p. 27). ACM.

[Barla et al. 2005]
Barla, P., Thollot, J., & Sillion, F. X. (2005, July). Geometric clustering for line drawing simplification. In ACM SIGGRAPH 2005 Sketches (p. 96). ACM.

[Orbay et al. 2011]
Orbay, G., & Kara, L. B. (2011). Beautification of design sketches using trainable stroke clustering and curve fitting. Visualization and Computer Graphics, IEEE Transactions on, 17(5), 694-708.

[Thiel et al. 2011]
Thiel, Y., Singh, K., & Balakrishnan, R. (2011, October). Elasticurves: exploiting stroke dynamics and inertia for the real-time neatening of sketched 2D curves. In Proceedings of the 24th annual ACM symposium on User interface software and technology (pp. 383-392). ACM.

[McCrae et al. 2009]
McCrae, J., & Singh, K. (2009). Sketching piecewise clothoid curves.Computers & Graphics, 33(4), 452-461.

[McCrae et al. 2011]
McCrae, J., & Singh, K. (2011, August). Neatening sketched strokes using piecewise french curves. In Proceedings of the Eighth Eurographics Symposium on Sketch-Based Interfaces and Modeling (pp. 141-148). ACM.

[Lu et al 2012]
Lu, J., Yu, F., Finkelstein, A., & DiVerdi, S. (2012). HelpingHand: example-based stroke stylization. ACM Transactions on Graphics (TOG), 31(4), 46.

[Tomasi et al. 1998]
Tomasi, C., & Manduchi, R. (1998, January). Bilateral filtering for gray and color images. In Computer Vision, 1998. Sixth International Conference on(pp. 839-846). IEEE.

[Marr and Hildreth, 1980]
Marr, D., & Hildreth, E. (1980). Theory of edge detection. Proceedings of the Royal Society of London. Series B. Biological Sciences, 207(1167), 187-217.

[Winnemöller et al. 2006]
Winnemöller, H., Olsen, S. C., & Gooch, B. (2006, July). Real-time video abstraction. In ACM Transactions On Graphics (TOG) (Vol. 25, No. 3, pp. 1221-1226). ACM.

[Winnemöller, 2011]
Winnemöller, H. (2011, August). XDoG: advanced image stylization with eXtended Difference-of-Gaussians. In Proceedings of the ACM SIGGRAPH/Eurographics Symposium on Non-Photorealistic Animation and Rendering (pp. 147-156). ACM.

[Grimson and Grimson, 1981]
Grimson, W. E. L., & Grimson, W. E. L. (1981). From images to surfaces: A computational study of the human early visual system (Vol. 4). Cambridge, MA: MIT press.

[Marr, 1982]
Marr, D. (1982). Vision: A computational investigation into the human representation and processing of visual information, Henry Holt and Co. Inc., New York, NY.

[Canny 1986]
Canny, J. (1986). A computational approach to edge detection. Pattern Analysis and Machine Intelligence, IEEE Transactions on, (6), 679-698.

[Kang et al. 2007]
Kang, H., Lee, S., & Chui, C. K. (2007, August). Coherent line drawing. InProceedings of the 5th international symposium on Non-photorealistic animation and rendering (pp. 43-50). ACM.

[Kang et al. 2009]
Kang, H., Lee, S., & Chui, C. K. (2009). Flow-based image abstraction.Visualization and Computer Graphics, IEEE Transactions on, 15(1), 62-76.

[Kyprianidis et al. 2009]
Kyprianidis, J. E., Kang, H., & Döllner, J. (2009, October). Image and video abstraction by anisotropic Kuwahara filtering. In Computer Graphics Forum(Vol. 28, No. 7, pp. 1955-1963). Blackwell Publishing Ltd.

[Liu and You 2007]
Liu, L., Zhang, D., & You, J. (2007). Detecting wide lines using isotropic nonlinear filtering. Image Processing, IEEE Transactions on, 16(6), 1584-1595.

[Huang et al. 2010]
Huang, M., Yang, M., Liu, F., & Wu, E. H. (2010, December). Stroke extraction in cartoon images using edge-enhanced isotropic nonlinear filter. In Proceedings of the 9th ACM SIGGRAPH Conference on Virtual-Reality Continuum and its Applications in Industry (pp. 33-38). ACM.

[Buchanan and Mukundan 2012]
Buchanan, P., Doggett, M., & Mukundan, R. (2012, November). Structural vectorization of raster images. In Proceedings of the 27th Conference on Image and Vision Computing New Zealand (pp. 319-324). ACM.

[Kyprianidis and Kang 2011]
Kyprianidis, J. E., & Kang, H. (2011, April). Image and Video Abstraction by Coherence‐Enhancing Filtering. In Computer Graphics Forum (Vol. 30, No. 2, pp. 593-602). Blackwell Publishing Ltd.