I would like to create a panel for Photoshop which reads the composite, merged image of the current document, applies some effects to it, and mirrors it within the panel itself in realtime. Here's a mockup of what I'm trying to do, in essence:
I would use generator to fetch the pixels and write out a .png.
This can run from Your html panel, even though it is not the officially supported way.
Then spawn an ImageMagick process which can do a lot of stuff with the pixels:
After that, just read back and display the finished image.