halcon_ext op• Data kinds: image → feature
• Call: fullseye.apply(img, "hx_estimate_sl_al_lr", a=0.5, b=0.5) (the 2-D model is one image plus two scalar knobs a,b∈[0,1])
• HALCON equivalent: estimate_sl_al_lr (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).*
Lee-Rosenfeld: estimate the light source's slant (zenith angle, 0 = head-on to pi/2 = grazing). Normalised to [0,1].
Fits the image's mean luminance <I> to the relation of a Lambertian surface with reflectance 1, <I> = albedo * cos(slant), and returns slant = arccos(<I>) divided by pi/2 as np.float64 (0 to 1). 0 is frontal light (mean 1.0), 1 is fully grazing (mean 0).
• a, b are unused.
• The mean is clipped to [0,1] before being passed to arccos, so it never goes out of range.
In effect it is a 1-to-1 mapping "the lower the mean luminance, the larger the slant", with reflectance assumed to be 1 (a dark material also cannot be distinguished from oblique light). The gradient-corrected version is hx_estimate_sl_al_zc; a proxy for reflectance is hx_estimate_al_am. Use it as a guide when reproducing shading together with the elevation b of hx_shade_height_field.
• 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_estimate_sl_al_lr 0.50 0.50
▸ Load this pipeline · Load & run
• gallery2d_halcon_ext — py -3.11 examples/gallery2d_halcon_ext.py
feature as input)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.