Well I will not be much help but here is what i know.
Easel can import a SVG file or G-code. Also Easel has a App called “Image Trace” (the 2nd toolbar at the top of Easel, click on the Apps icon, it’s the 3rd to last in the Apps menu).
A post-processor, mainly is use in CAM programs think of a post-processor like a language translator, it translate from it’s code to G-code that X-Carve understands.
If you want a post-processor make the G-code then import that into Easel.
If you want to let Easel do the G-code
Inkscape is a free and popular vector graphics software (makes SVG files), I have used it, i think it’s easy and great to use. I did some Google searches and Inkscape can take a halftone file convert it to be saved as a SVG.
Here is a YouTube video Create Halftones In Inkscape Easily Without Cloning, https://www.youtube.com/watch?v=QHaPLOyQbeo
Well good luck and hopefully someone who as “done it” will reply for you.