A graphghan is a pattern for a crochet afghan that takes the form of a grid of coloured squares. It resembles the way in which images are represented digitally using a grid of squares known as pixels. Here is an example graphghan designed using Excel. The width of the pattern is 15 and the height is 15, making 225 pixels as a digital image. There are 4 different colours in the pattern, which means 2 bits would be required to store each pixel, as 4 different states can be represented in 2 bits. The storage requirements of the image would be 225 pixels x 2 bits = 450 bits.
There are two main ways to crochet a graphghan. The simplest is using a double crochet (UK) stitch for each square or pixel. Alternatively you can use the corner-to-corner (C2C) method, which involves crocheting squares working diagonally from the bottom right to the top left. This graphghan has been crocheted using the C2C method.
Simple compression methods such as Run Length Encoding (RLE) could also be applied to graphghans, compressing blocks of the same colour. For example, the second row could be simplified to 5W, 5Y, 5W.