Stencil Maker

Common questions

How do I turn a picture into a stencil?

Press Choose a picture, or drop one onto the dark stage: PNG, JPEG, WebP, GIF and BMP files open. Set the threshold from 0 to 255 and whether the darker or the lighter parts are cut. The islands line then says how many pieces would fall out; press Add bridge beside one, or Bridge all islands, until it reads 0. Then press SVG, PNG or Print. The example ring shows the whole process on a picture made for it.

What are islands and bridges in a stencil?

An island is a piece of the sheet that a cut surrounds, so nothing holds it once the stencil is cut: the centre of an O, or the disc inside a ring. A bridge is a strip of sheet left uncut across that cut, which joins the piece to the rest. In the example, a black ring 30 pixels thick leaves its 7,860 pixel centre loose, and one bridge 8 pixels wide across the top of the ring holds it, taking the cut from 12,248 to 12,008 pixels.

Why is a piece that touches the sheet at a corner still flagged?

Two squares that meet only at a corner share a point, not an edge, and a point has no width to hold material. So the sheet here holds together only through pixels that share a side, and a piece joined to the rest only at a corner is flagged as an island. Cut areas are treated the other way round: two cut pixels that meet at a corner count as one cut region.

What do threshold mode and edges mode do?

Each pixel's brightness is 0.299 times its red plus 0.587 green plus 0.114 blue, with any transparent part laid over white. Threshold mode cuts every pixel darker than the threshold, or lighter when Cut where is set to Lighter; a pixel exactly at the threshold is never cut. Edges mode cuts only a band inside each of those shapes, as wide as the edge width, from 1 to 50 pixels, measured to the nearest pixel on the other side with a diagonal step counted as one pixel; a shape thinner than twice that width is cut right through.

What does min region do?

Cut specks smaller than the min region, in pixels, are left as sheet, and islands smaller than it are cut away with the cut around them, so a single stray pixel does not become a cut or a loose piece of its own. The settings panel says how many of each it removed. Set it to 0 to keep every pixel. Bridges come after this step, so a bridge is never removed by it.

What is in the SVG and PNG files?

The SVG holds a white rectangle for the sheet and the cut shapes as one near-black path, traced along pixel edges, with the sheet sized in millimetres to the width on paper you set, from 10 to 2,000 mm. With Mark islands and bridges on, any islands and bridges are added as filled layers with the ids islands and bridges; with it off, the file holds only the sheet and the cut. The PNG holds the same pixels as the stage's Stencil view, at 1, 2 or 4 times their size. Both add a border of sheet, 4% of the picture's long side and at least 4 pixels, so a cut that reaches the picture's edge stays inside the sheet.

How big is the printed stencil?

Print opens the stencil on its own at the width on paper you set, and shrinks it to fit when the paper's printable area is smaller. For a stencil larger than one sheet of paper, the SVG carries the same size in millimetres.

Is my picture uploaded, and how large a picture can it open?

Nothing is uploaded. The picture is decoded and traced in this browser tab, and the page remembers only its settings, never the picture or its bridges. It works on the picture at up to 300, 600, 1,000 or 1,500 pixels on its long side, the Detail you choose, and never enlarges it. Before decoding, it reads the picture's declared size from its header and refuses one over 16,384 pixels a side or 100 megapixels, with a message saying so.