area_center_xld — 2D `features` op

• Data kinds: contour → feature

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

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

area_center_xld: 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

For the single contour with the largest number of points, computes the polygon area using the shoelace formula and returns it normalized by the total pixel count of the image. HALCON's `area_center_xld (Area and center of gravity (centroid) of contours and polygons.) is an operator that returns the centroid in addition to the area, but this stand-in returns only the area (the centroid information is lost in this approximation — a contractual constraint arising from the feature` sort being a single scalar).

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

`a, b` は未使用。輪郭が無ければ 0 を返す。

Detailed usage guide

• gallery2d_features 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.

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.

threshold 0.50 0.50
sk_find_contours 0.50 0.50
area_center_xld 0.50 0.50

▸ Load this pipeline · Load & run

Runnable examples (verified samples that actually call this op)

• gallery2d_features — py -3.11 examples/gallery2d_features.py

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

identity

Same category (`features`)

blob_count · area_frac · count_contours · total_length · vol_count · sk_euler · sk_entropy_feat · sk_blur_effect

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

area_center_xld — 2D features op