Unformatted text preview: ithin an image. The Hough transform can detect straight lines and curves (object
borders) if their analytic equations are known. It is robust in recognition of occluded and
noisy objects. Faculty of Engineering Robotics Technology MECH 4041 19
B.Eng (Hons.) Mechatronics S. Venkannah Mechanical and Production Engineering Department The generalized Hough transform can be used if the analytic equations of the searched
shapes are not available; the parametric curve (region border) description is based on
sample situations and is determined in the learning stage.
While forming the regions from complete borders is trivial, region determination from
partial borders may be a very complex task. Region construction may be based on
probabilities that pixels are located inside a region closed by the partial borders. Such
methods do not always find acceptable regions but they are useful in many practical
situations. Region based image segmentation:
Instead of partitioning an image, a region grower begins at one position in the image (often the
top left corner) and attempts to grow each region until the pixels being compared are too
dissimilar to the region to add them. Usually a statistical test is performed to decide if this is the
case. Haralick proposed a region growing technique, which assumes that a region is a set of
connected pixels with the same population mean and variance.
Region growing is a collection of segmentation techniques in which pixels are grouped in
regions called grid elements based on attribute similarities. Defined region can then be
examined as to whether they are independent or can be merged to other regions by means of an
analysis of the difference in their average properties and spatial connectiveness.
To differentiate between the objects and the background, assign 1 for any grid element occupied
by an object and 0 for background elements. It is common practice to use a square sampling grid
with pixels spaced equally along each side of t...
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