Photo to Sketch Converter

About the Photo to Sketch Converter

Turn a photo into a pencil sketch, clean line art, a charcoal drawing, a printable colouring page or a cartoon — each with sliders for line width, darkness, detail and more, and a before/after view to compare with the original. Colouring pages and sketches can be saved as a PDF that prints on A4 or US Letter paper, and several photos can be converted at once into one ZIP.

These are classical image-processing filters, not generative AI: every line comes from the brightness and colour edges already in your photo, so faces and objects are never invented or changed. All the work happens in your browser, in a background thread — nothing is uploaded.

How each style is made

• Pencil sketch — the classic colour-dodge technique: the grey image is divided by the inverse of a blurred negative copy (result = grey / (1 − blur(1 − grey))), so flat areas turn into white paper and only edges and texture remain as soft graphite strokes.
• Line art — the XDoG filter of Winnemöller, Kyprianidis & Olsen (Computers & Graphics 36(6), 2012): a difference of two Gaussian blurs of the CIE L* brightness, S = (1 + p)·G(σ) − p·G(1.6σ), followed by the soft threshold 1 + tanh(φ·(S − ε)) below ε. Edge emphasis is p, Ink level is ε, Crispness sets φ; Shading at 100% is the paper’s formula, and lower values lighten the brightness term so that large dark areas stay open.
• Charcoal — wide colour-dodge strokes, shadows filled in progressively, half of the drawing "smudged" with a blur, and a paper-grain texture.
• Colouring page — texture is smoothed with a guided filter (He, Sun & Tang 2013), then colour edges are found in the style of Canny (1986) on CIELAB, so a red flower on green leaves is outlined even when both are equally bright. Short fragments are removed and the lines are drawn at an even weight.
• Cartoon — edge-preserving smoothing, brightness quantised into a few soft-edged bands (Winnemöller, Olsen & Gooch 2006) and dark ink lines along edges.

Tips for good results

• Photos with a clear subject and a plain or blurred background give the cleanest colouring pages and line art.
• Busy textures (grass, gravel, fur) produce many lines: lower Detail, raise Remove small bits, or crop the photo first with the Image Cropper.
• For a sketch that keeps some tone, use Line art with more Shading, or Charcoal.
• Lines and textures are defined relative to the picture size, so the preview, the saved file and photos of any resolution look alike.

Printing colouring pages

Choose PDF for printing (A4) or (US Letter): each photo becomes one page, centred with 10 mm margins, in portrait or landscape to match the photo. In the print dialog choose "Actual size" or 100% so the margins are kept. Saved as PNG, the page is a pure black-and-white image you can also print from any photo app.

Limitations

• These filters follow the photo’s own edges; they do not redraw faces, change poses or add artistic details the way generative AI image tools do.
• Low-contrast or very noisy photos give weaker lines; increase the contrast of the photo first, or raise Detail and Edge emphasis.
• Saved images are at most 4,000 pixels on the long side, which is enough for an A4 print at over 300 dpi.
• The cartoon and colouring-page styles are the heaviest; on older phones a new preview can take a second or two.

Privacy

Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.