fullseye

halftone_screen — PRINTPATH `npr` op

データ種: image2d → image2d
呼び出し: import fullseye as fs; fs.ledger.halftone_screen(image, lpi=60.0, angle_deg=45.0, pixel_um=25.4, sharpness=8.0) (実装を直接呼ぶなら import printpath; printpath.halftone_screen(image, lpi=60.0, angle_deg=45.0, pixel_um=25.4, sharpness=8.0)、台帳から引くなら opsprintpath.get("halftone_screen"))

使い方

A classic rotated halftone screen — dots whose area carries the tone.

Thresholds the image against a rotated periodic spot function (the product of two shifted cosines, the classical round-dot screen). lpi is lines per inch and pixel_um the pixel pitch, so the screen frequency in pixels follows the printing convention rather than a bare “period in pixels”.

★Why this earns its place: two screens at different angles beat against one another, and the period and direction of that moiré are a closed form (:func:halftone_moire_period) that can be predicted before anything is drawn and then measured out of the image. That is why newspaper printing puts the plates at 15°/45°/75° — the beat is pushed to a frequency the eye does not resolve — and this op lets that be shown as numbers, not folklore.

Parameters

image : 2-D array in [0, 1] Tone; 0 prints solid, 1 prints blank (the ink is 1 - image). lpi : float Screen ruling, lines per inch. Newspapers use 65-85, magazines 133-175. angle_deg : float Screen angle. The classical set is K 45°, M 75°, C 15°, Y 0°. pixel_um : float Pixel pitch in micrometres (25.4 um = 1000 dpi). sharpness : float Edge hardness of the dot; large values give a hard threshold.

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

Raises ValueError: non-positive lpi, pixel pitch or sharpness; a screen period below 2 px (it would alias — reported, never silently drawn); a non-finite or oversized image.

Limits: this is a screen, not a printer. Dot gain, ink spread and registration error are not modelled, so measured ink is the geometric coverage and will read lighter than a real press.

詳しい使い方ガイド

printpath ファミリガイド

参考(サンプルデータ・文献)

サンプルデータカタログ(DL URL / ライセンス) — 2-D は skimage.data(BSD/public)+ 合成、3-D は実データ源(Stanford/PDS 等)の DL URL。
演算子の来歴・参考文献 — この op 族の元になった研究/手法の出典。
アルゴリズムの正典(著者・年)と用途は上記ファミリ使い方ガイドに記載。

実行できる例(この op を実際に呼ぶ検証済みサンプル)

poc_beats_fringes_and_screens — py -3.11 examples/poc_beats_fringes_and_screens.py
poc_print_registration — py -3.11 examples/poc_print_registration.py

型が繋がる次の op(`image2d` を入力に取れる)

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

同カテゴリ(`npr`)

halftone_moire_period · engrave_lines · hatch_field · mosaic_tiles_sites · mosaic_tiles_render

Provenance: printpath.py — PRINTPATH operator registry. この per-op ノートは tools/opdocs.py md が自動生成(手編集しない)。

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