Turning a photograph into line art sounds like it should be simple, and the version of it that most people picture involves very little skill and very little thought. The trouble with the usual filters is that they lay a texture over the top of the picture, so the result still looks like a photo with a pattern stuck on it. This one works differently.
What it actually does
The tool reads the structure of your image and redraws it as strokes. It looks at where edges are, where contrast is strong, and where texture gathers, and it builds line work that follows those features. That is why a portrait sketch traces the outline of a face and the shadows under a cheek, while a landscape sketch follows branches and rooflines. The strokes belong to your photograph rather than sitting on top of it.
Which photographs work best
Line art lives or dies on contrast, and this is the one thing worth checking before you start. Images with clear directional light, a distinct subject against its background, and visible texture give the strongest results. A flat, evenly lit scene in haze or fog produces a faint sketch that looks washed out, because there is simply not enough tonal change for a pencil to react to.
Portraits usually work well because faces are full of soft edges that a pencil can follow. Landscapes work well when there is a clear subject. The hardest cases are busy interiors and heavy digital noise, where the tool has too many edges to choose between.
A practical way to improve a weak source
If the sketch comes out too faint, the answer is usually in the original rather than in the tool. Raising brightness and contrast before converting makes the tonal range wider, and a wider tonal range gives the stroke generator more to work with. Cropping tighter onto the subject removes competing detail that would otherwise be sketched alongside the thing you care about.
Where this gets used
A sketched portrait makes a convincing illustration for a page that would rather not carry a photograph. Sketched product shots suit printed material and packaging concepts. For social posts, a sketch of a photograph is often the fastest way to get an image that looks designed rather than captured.
The whole thing runs in the browser, so the photo is never uploaded and you can work on pictures of people or property without sending them to a server.
Applying it more than once
Running a sketch effect over its own output produces something quite different from running it once. A single pass gives you a light, clean drawing that still resembles the original closely. A second pass finds the lines the first one produced and reinforces them, and the result reads as heavier and more graphic, closer to an ink drawing than to a pencil one. A third goes further and starts losing the fine tonal detail that made the first pass look like a sketch rather than a filter. Two passes is usually the useful limit.
It also helps to be clear about what you are choosing between. A light single pass suits an image that should still feel like the photograph it came from. A heavy double pass suits something going into a layout where it needs to hold its own against other elements.
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