[slowsmile]

Gregg...This plugin does two things:

1. If an svg image is detected in your epub then the image will be dual formatted to display an svg image for KF8 devices and will also be formatted as a jpeg image(in pixels) for display on older KF7 devices. The svg formatting is also not changed at all.

2. If a jpeg image is detected in your epub then the image will be dual formatted to display a jpeg image for a KF8 device with height/width as a % of current screen width and will also be formatted to display as a jpeg image(in pixels) for older KF7 devices.

The above image selection is wholly dependant on which Kindle device is currently running your ebook -- whether its a KF8 or KF7 device. The identification of the device -- whether KF8 or KF7 -- is completely handled by the media queries in your stylesheet. This means that the media queries can also automatically turn on and turn off these device-dependant html image displays as required.

"And how does KFX figure into all of this?"
It doesn't. This plugin is only for epub 2. KFX essentially means that every page in your ebook becomes a jpeg image that is always 100% max page size. This plugin is only really useful for smaller images that are less than max page size.

"And 630 seems to be a great number for the base width, but what is the reasoning behind it (especially considering specific devices)?"
This only applies to % h/w image sizing for KF8 devices. The base width is just a ballpark value because of the large variance of different-sized KF8 device screens out there now -- on both past and present devices. The whole thing -- using simple maths -- is described in my release notes for this plugin. Basically if you increase the base width(i.e. > 630px) then all KF8 image sizes will get smaller throughout your epub and if you decrease the base width(i.e. < 630px) then all your KF8 images will get larger. That's all you really have to know. If you want to increase/decrease individual % h/w sizes(for KF8 only) for a particular image then you will have to do that manually within the relevant image tag in the html.

The pixel h/w values used above for older KF7 devices are fixed or absolute values. So you must get those pixel image dimensions right for the KF7 screen when you initially size the original image because there is no safe way of adjusting absolute pixel values in situ for such images without problems.