Turn a Photo into a Sketch

The effect is the classic color-dodge sketch, a technique artists have passed around since the early days of digital editing: convert the photo to greyscale, make an inverted copy, blur that copy, then divide the grey image by the blurred inversion. Wherever a pixel closely matches its blurred surroundings, the division cancels out to near white - which is why flat areas like skies and walls vanish into paper. Wherever there is an edge, the mismatch survives division and remains as a dark line, which is how photographic edges become pencil strokes.

One control does most of the work: the blur radius. A small radius keeps only the tightest transitions, producing fine, spidery linework like a hard pencil; a large radius lets broader tonal shifts survive, giving softer shading like the side of a graphite stick. Try both extremes on the same photo - it can look like two different artists drew it.

Source choice matters more than settings. Portraits against plain backgrounds, pets with defined fur direction, architecture and line-heavy still lifes convert beautifully. Busy scenes turn to visual noise because every leaf and pebble becomes a stroke, and low-light photos are the worst input of all: sensor noise reads as texture to the algorithm, and the "sketch" fills with scribble that was never in the scene.

Because the pipeline is pure arithmetic rather than a generative model, the same photo at the same settings yields the same sketch every time - there is no prompt, no seed and no randomness. If you plan to print the result large, upscale the photo first and then convert, so the linework is computed at the final print resolution.