xg_crop_contours — 2D `xldgeom` op

• Data kinds: contour → contour

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

xg_crop_contours: 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.*

Sweeping knob a (0.1 / 0.5 / 0.9, the other knob at its default):

▸ xg_crop_contours: knob a sweep (docs site)

*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):

▸ xg_crop_contours: stages (docs site)

On other images (synthetic scene / photo / coins. Top row: inputs, bottom row: their outputs. Knobs at default):

▸ xg_crop_contours: other inputs (docs site)

Usage

Keep only contour points inside the central a-fraction window of the shape.

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

画像中心に置いた、高さ `a*H、幅 a*W` の矩形窓の内側にある輪郭点だけを

残す(`a は [0,1] に clip、b は未使用)。窓は行 [(0.5-a/2)H, (0.5+a/2)H]`、

列 `[(0.5-a/2)W, (0.5+a/2)W] の閉区間。H, W は辞書の shape` から取り、

無ければ全点の最大座標+1 で代用する。

返り値は `{"shape": (H, W), "cs": [...]}`。窓内に 1 点も残らない輪郭は捨て、

`a=0 では中心線上に正確に乗る点しか残らないためほぼ空、a=1` で全点が

残る。

注意: 窓に切られた輪郭は分割されない。残った点をそのまま 1 本の折れ線として

繋ぐので、輪郭が窓を出入りするたびに「窓の縁を飛び越える辺」が生まれ、

`xg_area_center` の面積や折れ線長が実際より大きく出る。切り口を正しく

扱いたいなら、領域の段階で `r3_clip_region` を掛けてから輪郭を取り直す。

座標は (row, col)。長さで輪郭ごと選別するのは `xg_clip_contours`。

Detailed usage guide

• gallery2d_geometry 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
xg_crop_contours 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 (`xldgeom`)

xg_moments · xg_area_center · xg_eccentricity · xg_orientation · xg_elliptic_axis · xg_height_width_ratio · xg_regress_contours · xg_clip_contours

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

xg_crop_contours — 2D xldgeom op