sp_saddle_points_sub_pix — 2D `subpix` op

• Data kinds: image → contour

• Call: fullseye.apply(img, "sp_saddle_points_sub_pix", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])

• HALCON equivalent: saddle_points_sub_pix (the HALCON reference is a useful guide to its meaning and parameters)

sp_saddle_points_sub_pix: 入力 → 出力

*The figure is the real output on a synthetic 128×128 input. Left: input, right: output (a non-image return value is shown as the value itself).*

Usage

Detects saddle points of the gray-value surface with sub-pixel accuracy (equivalent to HALCON `saddle_points_sub_pix`).

> The detailed description below is the original text — the summary and the headings are translated.

3x3 の 2 次曲面フィットのヘッセ行列が不定符号（`det H < 0、両主曲率の符号が逆）になる画素を鞍点候補とし、勾配 0 点がセル内（|dx|,|dy| <= 0.5）に収まるものだけを残す。a は鞍点の強さ（より小さい方の主曲率の絶対値）のしきい値を 1e-4〜0.0201 に振る（thr = 1e-4 + 0.02*a）。b` は未使用。戻り値は CONTOUR、座標の単位は入力画像のピクセル。

Detailed usage guide

• gallery2d_geometry family guide

Background guides (the physics and conventions behind this op)

• measurement_uncertainty — 計測の不確かさと校正の知識 — 「測れている」を主張するために

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.

Try it in Studio

The program below has been verified to run (same input as the figure). In Studio's help this block becomes buttons that load and run it on the spot.

sp_saddle_points_sub_pix 0.50 0.50

▸ Load this pipeline · Load & run

Runnable examples (verified samples that actually call this op)

• gallery2d_geometry — py -3.11 examples/gallery2d_geometry.py

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

identity · select_contours · smooth_contours · fit_line_contours · contours_to_region · count_contours · total_length · select_contours_xld

Same category (`subpix`)

sp_local_max_sub_pix · sp_local_min_sub_pix · sp_critical_points_sub_pix · sp_plateaus · sp_lowlands_center

*Provenance: ops.py — 2D operator registry. This per-op note is generated by tools/opdocs.py md (do not hand-edit).*

sp_saddle_points_sub_pix — 2D subpix op