Adaptive Shape Contour Tracing AlgorithmSUMMARYIn this article, we will introduce a new shape contour tracing algorithm called ¡§Adaptive Contour Tracing Algorithm¡¨. The algorithm can draw discontinuous open and closed digital shapes and return an ordered set of boundary points that represent the outline of the shape. Unlike other algorithms that return boundary points that are part of the drawn shape, our algorithm returns background points adjacent to the shape outline. Additionally, the algorithm is not bothered by noisy and ill-defined shapes because it can adapt to interruptions in the shape's contour using a predefined tolerance and is able to scan multiple neighbors of a given point. The algorithm has low complexity and no restrictions on the type or size of the shape drawn. The extracted ordered set of boundary points represents the contour of a given shape and is important for curvature-based shape descriptors. Subject categories and descriptors I.4.6 [Image processing and computer vision]: Segmentation ¡V Edge and feature detection, pixel classificationGeneral conditionsAlgorithms. KeywordsImage processing; Contour tracing; Extraction of shape boundaries.1. INTRODUCTIONContour tracing is an important process in boundary-based shape matching. All shapes are represented by a pattern of pixels, and edge pixels are usually a small subset of this pattern. Curvature-based shape matching methods rely on edge pixels to describe shape irregularities and a reliable edge tracing algorithm is required to extract the shape boundary. If the shape has holes, another hole finding algorithm must be applied to extract the hole pattern and such an algorithm is not part of this article. We have developed a sequential contour tracing algorithm called ¡§Adaptive Contour Tracing Algorithm¡¨. The algorithm calculates the surrounding contour of any shape and adapts to all types of closed curve representations, whether filled or partially filled digital shapes. Any pixel, 1 pixel wide lines and complete shapes can be drawn and represented by closed curves. The algorithm also takes into account discontinuities in the shape outline and can reach nearby pixels. Drawing the outline starts from the top left point or pixel closest to the shape and continues in a clockwise direction following the surroundings of the shape outline rather than the outline itself. The path around the contour is traced in a prospective scanning pattern to find the next closest surrounding point to the contour. The path is then closed when the starting point is found.