There is no reference to Figure 1.8 in the exercises at the end of Chapter 1. Maybe it is supposed to be associated with Exercise 1 (produce a figure with an exact pixel size)? If so, some reference to the figure in that section of the text would be helpful. And if it is supposed to be an example of setting exact figure pixel size, the code for Fig 1.8 could be more specific about defining what the figure pixel size is.

As a side note, the method of generating Fig 1.8 is interesting but perhaps unnecessarily complicated for this part of the book? Is it demonstrating something discussed in Chapter 1?