hx_lowlands — 2D `halcon_ext` op

• Data kinds: image → region

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

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

hx_lowlands: 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):

▸ hx_lowlands: 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):

▸ hx_lowlands: 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

Detect the basins of the grey values (flat local minima): the region of pixels equal to their neighbourhood minimum.

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

`ndimage.minimum_filter(size 角の正方形窓、鏡映境界)で局所最小 mn を取り、v <= mn + 1e-6` かつ

`v < 画像平均` の画素を 1 とする 0/1 の float region を返す。

• `a → 窓の一辺 size = 3 + int(a*6)`(3〜9 画素)。大きいほど広い範囲で最小である必要があり、点が減る。

• `b` は未使用。

平坦な窪みは窓内の全画素が最小値に等しいため、領域ごと(1 点ではなく面で)拾われる。逆に画像全体が平坦だと

`v < mean` を満たす画素が無く空になる。「平均より暗い」条件のため、明るい面の中の浅い窪みは拾えない。

雑音があると小さな極小が大量に出るので、前段に `hx_mean_shape / gauss_filter` を置く。反対の隆起は

画像を反転して同じ op を掛ける。

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.

hx_lowlands 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 `region` as input)

identity · reg_erode · reg_dilate · reg_open · reg_close · fill_holes · select_largest · remove_small

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_lowlands — 2D halcon_ext op