Strokes based shape description and processing

• Main Author: Tan, Wendell Yan Wei.
• Other Authors: Zheng Jianmin
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Computer science and engineering::Computing methodologies::Computer graphics
• Online Access: http://hdl.handle.net/10356/40056
• Institution: Nanyang Technological University

This report describes the development of a software application which enables a user to perform artistic brushstroke paintings using Catmull-Rom spline curve representation. The Catmull-Rom spline is one of the various functions available to approximate curves. The user will work on a 2D interface to perform brushstroke paintings on a drawing canvas and also have the ability to edit his drawings. The application is also to perform simple animation where one drawing is to morph into another drawing. The work progress of the software is documented and future enhancements are included. Brushstroke curve representations have been implemented using other various methods. One example is the Disk B-Spline curve representation. In this project, the Catmull-Rom spline method is explored to create brushstroke representations. As the user drags the mouse across the drawing canvas, control points are obtained and the Catmull-Rom spline function uses these points to calculate the central curve points of the stroke. The thickness of the brushstroke is determined by a radius at each curve point within the brushstroke. Conventional brushstroke painting requires a user’s pressure input to determine the thickness of the stroke drawn. A method to emulate this pressure input is discussed. However in this application, the traditional Chinese calligraphy style brushstroke is implemented where the brushstroke starts with a larger radius and decreases as the stroke is being drawn. Using a computer software application to draw paintings has its advantages and one of them is the ability to do editing. As the user edits the brushstrokes by changing its shape, the curve of the brushstroke is maintained using the Catmull-Rom spline function. The user can also edit the thickness of the brushstroke by changing the radius at each control point. The animation part of this application requires the user to draw a picture and this same picture is being edited by changing the shape and thickness of the brushstrokes in the drawing. The animation then shows the first picture morphing into the second picture with each edited point moving to its new location point-by-point at each “frame”.