Three Practical Stencil Case Studies

Compare downloadable sources and actual two-color outputs, then learn why a physical stencil sometimes needs manual editing.

Before you start

The portrait and cat outputs use this generator’s processing functions, not generative AI. Select Classic Black & White after uploading, then enter the settings below instead of the automatically suggested settings. Images are processed at a maximum edge of 1500 pixels. Cropping must be done in another editor.

These are digital comparisons, not physically cut or printed tests. No example guarantees compatibility with a cutting machine. Black means the area to remove in the paper diagram; white means material to retain.

Open the example library to load these images with their exact settings. Numbered markers below identify inspection areas, not automatically detected defects. They are page overlays and are not included in downloads.

1. Portrait: compare shadows, not just detail

Source portrait: 600 × 468 pixels.
Source portrait: 600 × 468 pixels.
Edge strength 0.7; threshold 100.
Edge strength 0.7; threshold 100.
Edge strength 0.3; threshold 150.
Edge strength 0.3; threshold 150.1. Inspect the cheek shadow: darker regions can replace lighter facial detail.2. Inspect small features around the eye before deciding whether to keep or manually simplify them.

Source photograph by Rachel McDermott, used under the Unsplash License; it is not a photograph taken by this site’s maintainer.

  1. Download the portrait and upload it to the generator.
  2. Select Classic Black & White. Set edge strength to 0.7 and threshold to 100. Save a PNG.
  3. Change edge strength to 0.3, then threshold to 150. Wait for the preview to settle and save a second PNG.
  4. Compare the forehead, cheek and hair at full size. The second setting changes the balance of facial shadows; it is not universally better and can sacrifice lighter details.

Small disconnected white areas may still need bridges for a physical stencil. A recognizable preview does not establish that every piece will stay attached.

A controlled adjustment sequence

  1. Load “Portrait · 0.7 / 100” from the example library and save a baseline PNG.
  2. Change only edge strength to 0.3, keeping threshold at 100. Compare the same cheek and eye regions in the synchronized zoom panels.
  3. Then change only threshold to 150. Save another PNG and compare it with the baseline. The shown 0.3 / 150 result combines both changes; it does not prove which individual control caused every difference.

If the face becomes less recognizable, restore the previous value rather than continuing to increase contrast. If an important feature remains disconnected, parameters alone may not solve it: simplify the shape or add a bridge in an external editor.

2. Cat: isolate the composition before adjusting settings

Full source: 400 × 600 pixels.
Full source: 400 × 600 pixels.
Full image; edge 0.5, threshold 130.
Full image; edge 0.5, threshold 130.
Head crop: 320 × 330 pixels.
Head crop: 320 × 330 pixels.
Same settings on the cropped image.
Same settings on the cropped image.3. Small forehead regions remain after cropping; check whether they add useful detail or become unwanted pieces.4. Thin whisker shapes need inspection at the intended print size.

Photograph by Zoë Gayah Jonker, used under the Unsplash License.

  1. Download the full source. Use edge strength 0.5 and threshold 130 with Classic Black & White.
  2. In an image editor, crop from x=40, y=72 to a width of 320 and height of 330 pixels. Alternatively, download the exact crop.
  3. Upload the crop and apply the same settings. Compare the head silhouette and the thin whiskers.

Cropping removes unwanted composition, not noise automatically. Forehead specks and fragile whiskers can remain. Local thresholding can also change pixels near a crop boundary because their neighboring pixels differ. At equal printed width the cropped head is larger, but its source has fewer pixels.

What to change next

Load “Cat · full image” and “Cat · head crop” separately; both start at edge 0.5 and threshold 130. Save each PNG before replacing the source. Compare composition first, without changing settings. Then try a small edge-strength change on the crop and inspect markers 3 and 4 again. Keep the change only if it preserves the silhouette you need.

When forehead specks or whiskers remain unsuitable, manually remove nonessential details in an image editor. For physical cutting, do not assume a line is strong enough because it is visible at 300% zoom: print at the intended dimensions and inspect or test the material.

3. Paper: keep the center attached with a bridge

A complete black ring leaves an unattached white center.
A complete black ring leaves an unattached white center.
A manually drawn white bridge connects the center to the sheet.
A manually drawn white bridge connects the center to the sheet.5. The retained white strip interrupts the cut ring and connects the center to the outer sheet.

These original vector diagrams were drawn for this guide. They are not automatic generator output and have not been physically cut-tested.

  1. Download the original diagram and open it in a vector editor.
  2. Add a white rectangle at x=300, y=186, width=140, height=28. It crosses the black ring. Download the edited example to compare.
  3. Set the whole document width to 150 mm. The bridge height is then 28 ÷ 600 × 150 = 7 mm. This is an example dimension, not a universal safe minimum.
  4. Print at actual size without fit-to-page. Check dimensions with a ruler and make a scrap-paper test before selecting stronger material. Follow the safety instructions for your cutting tools.

A narrower bridge changes the painted shape less but can tear more easily. Material, blade, design size and handling determine a useful width. This generator warns about structure but does not add bridges.

Next steps

Use PNG for initial previews. Experimental SVG may contain many small paths and needs inspection in your editor; it is not a machine-ready guarantee. PDF and automatic multilayer export are not available.

Read the beginner guide or the settings and structure guide before preparing a final file.