Start with the circular composition
This workshop takes the center square of the image, then uses only the inscribed circle. A face near a corner may be cut away. Crop your photo in an image editor first so the important features sit comfortably inside a circle; leave breathing room around ears, hair and lettering.
Large dark shapes on a light background are a useful starting point. A busy background competes with the subject because every strand can only add darkness. Transparent pixels are composited over white before conversion.
Understand what the preview measures
The optimizer compares a 128 by 128 grayscale target with straight strands connecting the selected nails. At each step it chooses a permitted next nail that reduces the model error, while keeping one continuous path. It does not infer missing facial features or reconstruct a damaged image.
Contrast changes the balance of light and dark before optimization. Compare the processed source beside the winding preview, and try a smaller number of steps before committing to a long build. The model treats thread coverage approximately; actual thread finish, lighting, board color and tension can change the result.
Match detail to the work you want to do
More nails create more possible line directions but require more physical preparation. More winding steps require more time and thread. Fine text and tiny highlights may remain unreadable even at the maximum settings. The upper limit is a practical browser and project-size limit, not a quality target.
Start with the owl demo to learn the numbering and player. For a valuable portrait, make a small physical test with the same board and thread and compare it under the lighting where the finished work will hang.