A histogram shows the statistical frequency of data distribution within a dataset. In the case of remote sensing, the dataset is an image. The data distribution is the frequency of pixels in the range of 0 to 255, which is the range of 8-byte numbers that are used to store image information on computers.
In an RGB image, color is represented as a 3-digit tuple with (0,0,0, 0, 0) being black and (255,255,255) being white. We can graph the histogram of an image with the frequency of each value along the y-axis and the range of 256 possible pixel values along the x-axis.
Remember in Chapter 1, Learning about Geospatial Analysis with Python, in the Creating the simplest possible Python GIS section, when we used the Turtle graphics engine included with Python to create a simple GIS? Well, we can also use it to easily graph histograms.
Histograms are usually a one...