I created a new 40x96 pixel RGB file, with an eye to making a liftplan for my 40-shaft loom; I filled it with 50% gray. I then converted it to Grayscale, then to Bitmap with Diffusion Dither method. Here are the before and after results:
Oddly enough, if you start with a grayscale image instead of RGB, the results are not satisfactory; but if you start with RGB, then convert down, it works! Try it.You will notice that this image, if applied as a liftplan for a straight threading, has some very long floats. The file needs a bit of touching up if it is to be usable. Adding an overlay consisting of risers and sinkers appropriately spaced is the ticket. Here is the file after converting back to RGB and an 8-end satin overlay applied as a layer style. Notice that now there are no floats longer than 7 in either direction. It is a weavable crepe weave on a straight draw.
Here's a drawdown, with four threading repeats and two liftplan repeats. No float longer than 7. Click to enlarge. I'll be talking about overlays at Complex Weavers Seminars this summer. Come join the fun!