edges op• Data kinds: image → image
• Call: fullseye.apply(img, "xsk2_inv_gauss_grad", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
*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):
▸ xsk2_inv_gauss_grad: knob a sweep (docs site)
*Knob b does not change the output (measured: identical at 0.1 / 0.5 / 0.9).*
On other images (synthetic scene / photo / coins. Top row: inputs, bottom row: their outputs. Knobs at default):
▸ xsk2_inv_gauss_grad: other inputs (docs site)
*No colour (H,W,3) input is shown: this op treats the colour channel as a third spatial axis (it crosses channels). Call it per channel.*
Inverse Gaussian gradient image (the edge-stopping function for Active Contour / GAC). Calls `skimage.segmentation.inverse_gaussian_gradient`.
> The detailed description below is the original text — the summary and the headings are translated.
a がエッジ感度 alpha（`50 + 150*a`、範囲 50〜200。大きいほど弱いエッジでも停止関数の値が下がる＝止まりやすくなる）を振る。b は未使用。値はエッジで小さく（0 に近く）平坦部で 1 に近い——geodesic activecontour 系のセグメンテーションでエッジ停止項として使うことを想定した出力で、そのまま見た目のエッジ画像として使うと通常のエッジ検出とは明暗が逆に見える。
Border handling: replicate the edge pixel (nearest neighbour) (measured; tools/impl2/border_probe.py).
Blank frame (measured): feeding an image of uniform brightness makes every pixel foreground (1), regardless of the brightness. A frame that is blown out, occluded, or simply has no subject comes back as “100 % defective”, so test for uniformity upstream and reject such frames.
• gallery2d_edges family guide
• 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.
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.
xsk2_inv_gauss_grad 0.40 0.50
▸ Load this pipeline · Load & run
• gallery2d_edges — py -3.11 examples/gallery2d_edges.py
image as input)identity · gaussian · mean_box · bilateral · unsharp · median · min_filter · max_filter
edges)sobel_mag · prewitt_mag · roberts_mag · dog · edge_transition_width · grad_dir · log · corner_response
*Provenance: ops.py — 2D operator registry. This per-op note is generated by tools/opdocs.py md (do not hand-edit).*
© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.