gray op• Data kinds: image → image
• Call: fullseye.apply(img, "invert", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
• HALCON equivalent: invert_image (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.*
*Knob a does not change the output (measured: identical at 0.1 / 0.5 / 0.9).*
*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):
▸ invert: 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).*
Tone inversion (negative-positive reversal). Equivalent to HALCON's invert_image (Invert an image.).
It just returns 1 - clip(v,0,1). a, b are unused.
• The input is first clipped to [0,1] and then inverted, so out-of-range values are inverted after saturating (1.3 → 0, -0.2 → 1). Normalise arrays whose range is not [0,1] in an earlier stage.
• The return value is a float of the same shape as the input, range [0,1]. NaN passes through clip and is returned as NaN (it is an op registered directly in ops.py, so the backend guard does not apply — to stop non-finite values, go through fullseye.apply with on_error="raise").
• Applying it 2 times restores the original (an involution). Applied to a region it swaps foreground/background, but for regions there is invert_region (complement).
• Where to use it: inverting before picking up a dark object as the "bright side" with threshold; turning the dark residual of dc_rpca_sparse or the black lines of xpil_contour into a positive signal; re-reading a distance transform's "darker further inside" as "brighter further inside".
• gallery2d_gray_arith 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.
invert 0.50 0.50
▸ Load this pipeline · Load & run
• gallery2d_gray_arith — py -3.11 examples/gallery2d_gray_arith.py
• genspark_external_review — py -3.11 examples/genspark_external_review.py
• poc_tacscalib_sphere_lut — py -3.11 examples/poc_tacscalib_sphere_lut.py
image as input)identity · gaussian · mean_box · bilateral · unsharp · median · min_filter · max_filter
gray)gamma · quantize_uniform · quantize_lloyd_max · quantization_error · dither_ordered · dither_floyd_steinberg · companding_mu_law · banding_map
*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.