Hello I'm a newbie here.....I can't find much on this direct subject so hope it is ok to post a question. My problem may be more associated with not knowing how to search for what I am looking for....and if so I apologies in advance.
Anyway, I am trying to create an optical mask from a photo...of the sort you would use to make a silk screen for printing t shirts for example and I need the image to be sharp areas of solid black and white. Because I started with a colour image, back ground areas that I need to be pure white are in varying shades of grey....the shade of grey being created by the low black pixel density.
I'm using GIMP and I wonder if anyone can show me how to perform a lithographic change to my image such that light grey (low pixel density) areas are converted to solid white and dark grey (high pixel density) areas are converted to solid black. It sounds like something that the threshold tool could achieve except that that works on a pixel by pixel basis and appears to be intended to convert coloured pixels to black or white...if I use it on my image it has no effect whatsoever (turns black pixels black and white pixels white making no difference to the overall image!).