Create a manually runnable tool (in internal.util) that walks through the java sources of the base classes, parses out the <img width="" height="" src=""/>, downloads the referenced image and verifies that height is set properly.
More specifically, round(640.0/image.width * image.height) and prints a fake stacktrace element to the particular line and the right amount. It is recommended the download is somewhat rate-limited (1 per 100ms) because the sheer number of images. The same reason applies why this isn't an unit test to be. Use TestHelper.findSource() to locate the source java.