I recently created a simple pattern generator from black and white images (aka 2 colors) using powershell. Anyone interested in it here is the script. You sadly have to enable scripts or copy paste the whole thing into a powershell ISE window. Make sure to update the file names. I haven't cleaned it up yet as I just barely got the logic side of it functioning. I did borrow stuff from a lot of sources and I will come back and edit this post to give credit where I can. It inverts the image so the pattern starts at the bottom of an image and then inverts every other line for when you rotate your workpiece.
I'm thinking of making something similar in something like Python to make it less OS specific. I'm debating also increasing it to making grid patterns instead of just text for those who like graphic images more. Here is an example of the text output for something I'm making as a gag gift for my sibling.
EDIT: File has been updated to prompt for file location and will save the pattern file in the same directory as the script using the input file's name. Please note that you will want to make sure your input file is black and white and small dimensions or it'll take forever. It will do the job regardless of the file size it just takes a very long time. Plus I don't know anyone that wants to filet a blanket using an image that is 1920x1080..... :P
Last Edit for this version: It will prompt to save. If you double click on a file to copy it's filename and hit save it'll say you're overwriting but you're actually not. It'll save with a .txt extension thus preserving the original. This is a default warning from microsoft so if there is a way to change it I'm not bothered to find out. It'll accept you keeping the extension in the name field or removing it as I've checked for both contingencies. Overall this is pretty much a complete package. I hope this helps someone.