All the histograms that we have seen being computed and/or plotted in this chapter so far have been one-dimensional histograms. This is because the pixel intensities were the only entities that were being aggregated into bins. Also, if you recall the parameters that we discussed for OpenCV's calcHist() function, you would remember that one of them explicitly specified the number of dimensions that the function is supposed to work with (we have passed the integer 1 as the parameter for all the invocations in the chapter so far). In this section, we will take a brief look at the concept of multidimensional image histograms and also see how we can modify the code that we have been working with to enable the calcHist() function to return a multidimensional histogram.
Before we dive into the code, let's understand what multidimensional histograms are and what they represent. If you think of the one-dimensional histograms that we have been dealing with so far...
