April 2019
Intermediate to advanced
336 pages
8h 22m
English
Content preview from OpenCV 4 for Secret Agents - Second Edition
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Detecting circles and lines
From The Living Headlights (our project in Chapter 5, Equipping Your Car with a Rearview Camera and Hazard Detection), we are already familiar with one technique for detecting circles. We treated the problem as a special case of blob detection, and we used an OpenCV class, SimpleBlobDetector, which allows us to specify many detection criteria, such as a blob's size, color, and circularity (or non-circularity, that is, linearity).
A blob is a shape filled with a solid (or nearly solid) color. This definition implies that many circular or linear objects are not detectable as blobs. In the following screenshot, we can see a sunlit desk with a china teapot, china bowl, and pewter bowl:
The bowls and the lid of the ...
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