A good friend of mine who is a self-published author has had some pictures created for one of his children's books, however the artist has painted the images with colour, and is now asking a fortune to provide blank (outline copies). I have been approached to remove the colour and provide outline images. Normally, if these were vector images or photos I would not have posted on here, however as they are painted images and therefore have different levels of colour within the same area on the image, I am having some difficulty cleaning up the images, does anyone have some tips for achieving this, that will not take too long to accomplish. There are about a dozen images to complete, some of which are more detailed than others... I have attached one of the images as an example...