engrave_lines — PRINTPATH `npr` op

• Data kinds: image2d → image2d

• Call: import fullseye as fs; fs.ledger.engrave_lines(image, spacing_px=6.0, angle_deg=0.0, gamma=1.0, max_width=0.95) (to call the implementation directly, import printpath; printpath.engrave_lines(image, spacing_px=6.0, angle_deg=0.0, gamma=1.0, max_width=0.95); from the registry, opsprintpath.get("engrave_lines"))

Usage

Copperplate engraving — parallel lines whose width carries the tone.

★Why this earns its place: while the lines do not touch, the ink coverage

of a ruling of width `w and spacing d is exactly w / d`. So the width

needed for a target tone is solved, not tuned: `w = (1 - tone) * d`. The

op therefore has a closed form to be graded against — blur the result and the

local mean must come back to the tone you asked for.

Parameters

----------

image : 2-D array in [0, 1]

spacing_px : float

Line spacing. The finest tone step a ruling can hold is `1 / spacing`.

angle_deg : float

gamma : float

Tone shaping applied before solving for the width (`tone**gamma`).

max_width : float

Widest line as a fraction of the spacing; 1.0 would make solid black and

lose the ruling.

Returns an `image2d`: 1 = paper, 0 = ink.

Raises `ValueError`: spacing below 2 px (the ruling cannot be sampled);

`max_width` outside (0, 1]; non-positive gamma; a non-finite or oversized image.

Detailed usage guide

• printpath family guide

References (sample data, literature)

• 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.

Runnable examples (verified samples that actually call this op)

• poc_beats_fringes_and_screens — py -3.11 examples/poc_beats_fringes_and_screens.py

Ops the type connects to (they accept `image2d` as input)

stipple_points_from_image · stipple_energy · stroke_tone_error · halftone_screen · hatch_field · mosaic_tiles_sites · mosaic_tiles_render · print_layer_defect_map

Same category (`npr`)

halftone_screen · halftone_moire_period · 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).*

engrave_lines — PRINTPATH npr op