I tell you what I think is a propher method
First of all, I recomend using a software like
FSIV. It provide both fast and eficient PNG compression. PNG image is much more suitable for diagrams and schematics because it takes less space AND looks better on screen than a jpg image. It can capture pictures from other program pretty easy.
You can make the picture even smaller (faster loading time) by recuce the number of colors to 256. Unfortunately fsiv doesn't count colors in the captured image itself, you have to go to the option menu when save image.
Irfanview DO count colors if using pngout extension. However, that one is serious slow and you'll probably get at least that good compression using fsiv instead.
Other image vievers that is also suitable is
XnView and
Irfanview.
I DONT like schematics posted as doc, docx or jpg. I LIKE schematics posted as PNG, GIF, PDF (If graphic is vector, I hate jpg's bundled into pdf).