A connected component often corresponds to the image of an object in a pictured scene. To identify this object, or to compare it with other image elements, it can be useful to perform some measurements on the component in order to extract some of its characteristics. In this recipe, we will look at some of the shape descriptors available in OpenCV that can be used to describe the shape of a connected component.
Many OpenCV functions are available when it comes to shape description. We will apply some of them on the components that we have extracted in the preceding recipe. In particular, we will use our vector of four contours corresponding to the four buffaloes we previously identified. In the following code snippets, we compute a shape descriptor on the contours (contours[0] to contours[3]) and draw the result (with a thickness of 2) over the image of the contours (with a thickness of 1). This image is shown at the end of this section...