hx_fit_ellipse_contour — 2D `halcon_ext` op

• Data kinds: contour → feature

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

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

hx_fit_ellipse_contour: input → output

*The figure is the actual output on a synthetic 128×128 input. Left: input, right: output. Point clouds are drawn as a top-down scatter (brightness = z), 1-D series as a line plot, volumes as the maximum-intensity projection along z, videos as the middle frame, complex images as magnitude; return values that are not pictures are shown as the values themselves.*

*Knob a does not change the output (measured: identical at 0.1 / 0.5 / 0.9).*

*Knob b does not change the output (measured: identical at 0.1 / 0.5 / 0.9).*

Stages (the ops that come before → this op, left to right):

▸ hx_fit_ellipse_contour: stages (docs site)

Usage

Fit an ellipse from the second moments and return the axis ratio (minor/major: 1 for a circle, toward 0 the more elongated).

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

全 contour の点をまとめて座標共分散行列の固有値 `λmin, λmax を取り、sqrt(λmin/λmax)`(主軸方向の標準偏差

の比 = 慣性楕円の短軸/長軸)を `np.float64` で返す。

• `a, b` は未使用。

• 点が 3 個未満、または `λmax <= 1e-9`(全点一致)なら 0.0。負の固有値は 0 に clip する。

1 に近いほど等方(真円)、0 に近いほど細長い。楕円境界を当てはめる代数的フィットではなく点群の 2 次モーメント

なので、点の密度の偏りや欠けた弧では軸比が変わる。楕円の傾き・中心は返さない(`orientation_xld` /

`area_center_xld)。cv2.fitEllipse 版は elliptic_axis_xld。楕円からの逸脱量は hx_dist_ellipse_contour`。

Detailed usage guide

• gallery2d_halcon_ext 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
hx_fit_ellipse_contour 0.50 0.50

▸ Load this pipeline · Load & run

Runnable examples (verified samples that actually call this op)

• gallery2d_halcon_ext — py -3.11 examples/gallery2d_halcon_ext.py

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

identity · feature_to_img

Same category (`halcon_ext`)

hx_gen_circle · hx_gen_ellipse · hx_gen_rectangle2 · hx_gen_checker_region · hx_gen_grid_region · hx_gabor · hx_fit_surface1 · hx_fit_surface2

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

hx_fit_ellipse_contour — 2D halcon_ext op