- What image types work best for tattoo stencil conversion?
- High-contrast black-and-white line art gives the cleanest results. Pencil sketches, ink drawings, or digital line art with a transparent or white background are ideal. Color photos and watercolor-style images can also work — use the Sobel edge mode and adjust the threshold until you see continuous lines without noise. SVG files are rasterized to 2000 px wide before processing, preserving sharpness.
- What is a thermal transfer stencil and why does the image need to be inverted?
- A thermal transfer stencil (also called a hectograph or spirit stencil) is a layered sheet you run through a thermal copier or press against skin after applying stencil lotion. The copier reads dark areas as the lines to transfer. Edge detection extracts the outlines of your design as bright values on a dark field — inverting flips this to black lines on white, which is what the copier or tracing method expects. Without the invert step, you'd get the outline of every white area instead of the design lines.
- How do I set the correct print size for my tattoo?
- Measure the area on the client's skin where the tattoo will go. Enter that width (in mm) in the "Print size — width" field. The tool calculates the proportional height automatically and places the design at exactly that size on the page. For example, a forearm piece 80 mm wide will print at 80 mm × (proportional height) on the PDF. You can choose 1, 2, or 4 copies per page to get multiple size options on one sheet.
- Does my image get sent to any server?
- No. Every step — file reading, grayscale conversion, edge detection, inversion, contrast adjustment, and PDF generation — runs entirely in your browser using the Canvas API and pdf-lib (a JavaScript library). Your design image is never uploaded anywhere. This also means the tool works offline once the page has loaded.
- What is the difference between Sobel, Laplacian, and Threshold mode?
- Sobel applies a 3×3 gradient kernel that detects horizontal and vertical edges separately and combines them. It produces smooth, continuous outlines and handles gradients well — best for most tattoo designs. Laplacian is a second-derivative operator that is sharper but more sensitive to noise; use it for very detailed, fine-line art. Threshold only skips edge detection and simply binarizes the grayscale image — any pixel darker than the threshold becomes a black line. This is best for bold traditional designs or solid fill areas where you want to reproduce the complete shape, not just the outline.
- Can I use this for hand-poked or machine tattoos?
- Yes — the stencil output is a standard print-and-transfer image. Print it on regular paper and use it as a reference, or print on dedicated stencil transfer paper (Spirit, Stencil Stuff brand) and apply directly to skin with stencil lotion. The "Line Thickness Boost" slider dilates the edges by 1–4 pixels so thin digital lines read cleanly after transfer, compensating for slight blur when transferring to skin.