So, to be absolutely clear:
There is no way to avoid the jagged edge problem when trying to size for every possible reader (including computers) using only one ISBN for all device in an epub.
I can tell it to do height:100% or max-height:100%, but as long as the image is sized for the largest resolution, if it needs to be shrunk the jagged edge thing will always occur, depending on the contrast and complexity of the image.
Also, you can convert to SVG. But the images are so large it's moot. Converting a JPEG to SVG caused it to be 40mb rather than 200k.
Is that the proper consensus?