halcon_ext op• Data kinds: image → image
• Call: fullseye.apply(img, "hx_gen_bandfilter", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
• HALCON equivalent: gen_bandfilter (the HALCON reference is a useful guide to its meaning and parameters)
*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_gen_bandfilter: knob a sweep (docs site)
Sweeping knob b (0.1 / 0.5 / 0.9, the other knob at its default):
▸ hx_gen_bandfilter: knob b sweep (docs site)
On other images (synthetic scene / photo / coins. Top row: inputs, bottom row: their outputs. Knobs at default):
▸ hx_gen_bandfilter: 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).*
An ideal band-filter image (an annulus in frequency, centre radius a and width b). A different operator from gen_bandpass.
> The detailed description below is the original text — the summary and the headings are translated.
`hx_gen_lowpass と同じ fftshift 済の正規化周波数半径 r`(中心=DC)に対し
`c - half <= r <= c + half の円環を 1 とする 0/1 の float 画像(周波数領域マスク)を返す。入力 v` は
形状の取得にのみ使う。
• `a → 円環の中心半径 c = 0.05 + 0.4*a`(0.05〜0.45)。
• `b → 半幅 half = 0.03 + 0.15*b(0.03〜0.18)。内半径 c - half` が負になる組み合わせ(小さい a と
大きい b)では DC を含む円板になり、実質ローパスになる。
`hx_gen_bandpass` が「内半径と幅」なのに対し、こちらは「中心と半幅」で同じ円環を指定する。特定の空間周波数
(縞の周期 `1/c 画素)だけを抜き出すマスクを作り、fft_generic` などの中心=DC スペクトルと画素積で使う。
Value comparability (measured): the output is normalised by that image's own maximum (the output maximum is always 1.0, and scaling the input leaves the output unchanged). Values therefore cannot be compared across images — a feature of the same strength takes a different value depending on what the strongest feature in that image happens to be, and in an image holding only weak features the noise is lifted to 1.0. To compare across images, rescale by a common reference.
• gallery2d_halcon_ext 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.
hx_gen_bandfilter 0.50 0.50
▸ Load this pipeline · Load & run
• gallery2d_halcon_ext — py -3.11 examples/gallery2d_halcon_ext.py
image as input)identity · gaussian · mean_box · bilateral · unsharp · median · min_filter · max_filter
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).*
© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.