什么原因导致WPF打印机输出被栅格化？

I've encountered many issues with printing in WPF where particular combinations of items being printed will suddenly trigger rasterization of the printer output (causing ugly and huge printer output, and can cause it to take 30 seconds to print each page). I've found that often things like having any level of opacity set on a control will trigger this. I forget what all else does it (I believe using a canvas with clipping turned on can do it as well), but now I'm running into yet another issue with a stackpanel with a tiled imagebrush filling a border... etc... which is now causing this rasterization yet again. I've encountered many issues with printing in W