npr op• Data kinds: none → table (an op determined by its arguments alone — it takes no image or data input)
• Call: import fullseye as fs; fs.ledger.halftone_moire_period(lpi_a=60.0, angle_a_deg=45.0, lpi_b=60.0, angle_b_deg=75.0, pixel_um=25.4) (to call the implementation directly, import printpath; printpath.halftone_moire_period(lpi_a=60.0, angle_a_deg=45.0, lpi_b=60.0, angle_b_deg=75.0, pixel_um=25.4); from the registry, opsprintpath.get("halftone_moire_period"))
The beat between two halftone screens — period and direction, in closed form.
Each screen is a frequency vector `f (cos t, sin t)`; where two screens
overlap the visible moiré is the difference vector, so its period is
`1 / |f_a - f_b|` and its direction is that of the difference. For equal
rulings the magnitude reduces to `2 f sin(dt / 2)`, which is why the beat
period grows without bound as the angle difference goes to zero — two plates
at nearly the same angle give a huge, very visible moiré.
★Why this earns its place: the prediction is available before any
screen is drawn, and :func:halftone_screen plus an FFT can measure the beat
out of the picture. Two independent routes to one number.
Returns a `table: period_px, angle_deg, freq_cycles_per_px`.
Raises `ValueError`: non-positive ruling or pitch; two screens that are
identical in both ruling and angle (the difference vanishes — there is no
beat, and returning `inf` silently would be worse than saying so).
• Sample-data catalog (download URLs / licences) — 2-D uses skimage.data (BSD/public domain) plus synthetic images; 3-D lists download URLs for real data sources (Stanford, PDS, …).
• Operator provenance and references — the sources of the research/methods this op family came from.
• The canonical algorithm (author, year) and its uses are named in the family usage guide above.
• poc_beats_fringes_and_screens — py -3.11 examples/poc_beats_fringes_and_screens.py
• poc_moire_screen — py -3.11 examples/poc_moire_screen.py
• poc_print_registration — py -3.11 examples/poc_print_registration.py
table as input)gcode_write · gcode_extrusion_volume · gcode_time_estimate · gcode_layer_image · contours_to_gcode
npr)halftone_screen · engrave_lines · hatch_field · mosaic_tiles_sites · mosaic_tiles_render
*Provenance: printpath.py — PRINTPATH operator registry. This per-op note is generated by tools/opdocs.py md (do not hand-edit).*
© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.