Good: black stencil on a white background
A flat black silhouette on a white background usually converts cleanly because the foreground and background are easy to separate. This works well for laser cutting templates, simple signs, decorative panels, gasket sketches, and workshop tracing patterns.
Before uploading, crop close to the part and remove unrelated text or borders. After conversion, inspect the generated DXF for extra inner contours and delete anything that is not part of the final geometry.
Good: scanned technical line drawing
Scanned line art can work well when the lines are dark, the paper is clean, and the drawing is viewed from directly above. Increase contrast before upload if the scan is gray or faded. Thin construction lines, colored fills, and handwriting can add unwanted geometry.
The DXF output should be treated as a tracing layer. For precise parts, redraw critical holes, slots, and edges in CAD after scaling the result.
Needs cleanup: photos of objects
Photos often include shadows, perspective distortion, highlights, and textured backgrounds. The converter may trace all of those visual details. If a photo is the only available source, place the part on white paper, shoot from directly above, use even lighting, and crop tightly.
A quick manual edit in an image editor can make a large difference: remove shadows, make the part black, make the background white, and export as PNG or JPG before uploading.