I've put some sources from the Rodrigues book here, some of which I've been able to adapt and get to work. Also, some of my own code.
The Rodrigues sources are available through his web page above, as .zip or .tar.zip.
First bit of code I got to work is this, based on his listing 17.1. This simply reads in a JPEG and reports on its size. (Hearthside is the Sun Ultra 5 I have at home.)
Here are two source files from Rodrigues from which things can be lifted, which should also help. Our goal should be to print out the image properties and figure out how to produce an array of doubles which are the magnitudes of each pixel, e.g, the gray levels. Have to worry about whether they're saved as color, etc.
Of course the image work we're doing for our tiny samples should work just as well for actual diagrams from the ASM journals. That is the point after all. But the tiny ones allow printing out the entire contents so we can be sure what we're doing.
Here are the sources for Rodrigues' ImageDataViewer.java and ImageInfoUtil.java, both from Chapter 8.
Here's a larger real image from a recent ASM journal, width=200 height=440.