trans_to_rgb — 2D color op

• Data kinds: color → color

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

• HALCON equivalent: trans_to_rgb (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).*

Stages (the ops that come before → this op, left to right):

▸ trans_to_rgb: stages (docs site)

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

▸ trans_to_rgb: other inputs (docs site)

Usage

The inverse transform from a color space back to RGB. Claimed to correspond to HALCON's trans_to_rgb (conversion from an arbitrary color space to RGB color space), but the implementation only supports the single direction HSV to RGB.

Whereas trans_from_rgb can choose among 4 colour spaces (HSV/Lab/YUV/XYZ) with a, this inverse transform always treats the input as HSV and applies cv2.COLOR_HSV2RGB. When called on Lab/YUV/XYZ it converts with a wrong interpretation of the colour space, so the output has broken colours. a, b are unused.

Detailed usage guide

• gallery2d_color_artistic family guide

Background guides (the physics and conventions behind this op)

• colorimetry — Colorimetry and spectra — colour is fixed only by spectrum × illuminant × observer

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.

cfa_to_rgb 0.50 0.50
trans_to_rgb 0.50 0.50

▸ Load this pipeline  ·  Load & run

Runnable examples (verified samples that actually call this op)

• gallery2d_color_artistic — py -3.11 examples/gallery2d_color_artistic.py

Ops the type connects to (they accept color as input)

identity · trans_from_rgb · linear_trans_color · principal_comp · rgb1_to_gray · rgb3_to_gray · access_channel · edges_color

Same category (color)

cfa_to_rgb · trans_from_rgb · linear_trans_color · principal_comp · rgb1_to_gray · rgb3_to_gray · access_channel

*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.