img_to_keypoints — 2D `bridge` op

• Data kinds: image → keypoints

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

img_to_keypoints: 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):

▸ img_to_keypoints: knob a sweep (docs site)

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

▸ img_to_keypoints: knob b sweep (docs site)

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

▸ img_to_keypoints: other inputs (docs site)

*The 4th column is a colour (H,W,3) input. This op handles colour without crossing channels (it does not convolve the colour channel as a third spatial axis).*

Usage

Turn the local maxima of the image into image-plane points (u, v) = (col, row), shape (N,2).

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

`scipy.ndimage.maximum_filter` で窓内最大と一致し、かつ値がしきい値以上の

画素を極大とする(同値の平坦部は全画素が極大になる —— 前段に `gaussian`

を置くと減る)。

• `a → 窓の一辺 k = 3 + 2 * int(a * 4)`(a=0.5 で 7。大きいほど疎)。

• `b → しきい値 thr = b`(値 ≥ thr の極大だけ残す。b=0 で全極大)。

• 返り値: `(N, 2) float64 の (u, v) = (col, row)`。値の降順、同値は

行優先で並ぶ(決定的)。極大が 1 つも無ければ (0, 2) —— 空でも形の

契約は満たすが、下流の op によっては空を拒否する。

• 画像の縁は `mode="nearest"` で処理するので縁の画素も極大になりうる。

使いどころ: `tb_keypoints_to_image2d`(点を画像に戻す)、

`tb_keypoints_uv_to_points`(z=0 の点群にする)への入口。

Detailed usage guide

• gallery2d_bridge 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.

img_to_keypoints 0.50 0.50

▸ Load this pipeline · Load & run

Runnable examples (verified samples that actually call this op)

• gallery2d_bridge — py -3.11 examples/gallery2d_bridge.py

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

identity · tb_keypoints_uv_to_points · tb_keypoints_to_image2d

Same category (`bridge`)

img_to_points · img_to_signal · img_to_projection_profile · img_to_counts · img_to_matrix · img_to_video · img_to_volume · img_to_lightfield

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

img_to_keypoints — 2D bridge op