Another alternative is to upload a photo to the Victoria and Albert Museum website. There you can choose from 3 different resolutions and whether or not you want only squares or squares and triangles. Voila! You get a diagram of your photo "digitized" into the resolution you chose and the colors needed. There is also a count of how many squares and triangles of each color you need (you pick the size). No software required, just a photo and your browser.