Which gamuts does HDR Gamut Plot Lab compare?

HDR Gamut Plot Lab compares sRGB or Rec.709, Display-P3, and Rec.2020 using D65 white points and primary coordinates.

Which HDR transfer curves are available?

The tone curve panel supports gamma 2.2, gamma 2.4, PQ ST 2084, and HLG BT.2100 with selectable HLG viewing environment.

Does HDR Gamut Plot Lab upload my images to a server?

No. Image analysis is performed in the browser on a temporary canvas and the tool is designed for zero-network color diagnostics.

Auric Artisan · Documentation

HDR Gamut Plot User Guide

A complete workflow guide for the HDR Gamut Plot Lab, including Rec.709, Display-P3, and Rec.2020 overlays, CIE xy and u-prime v-prime diagrams, PQ and HLG transfer curves, ICtCp and JzAzBz perceptual plots, tone mapping, research panels, image analysis, batch color conversion, exports, share URLs, and Library preset capture.

Published: May 24, 2026 Updated: May 24, 2026 Category: Guide Author: Chirag Bansal

Back to Documentation Auric Artisan Home

Overview

HDR Gamut Plot Lab is built for HDR color review and color-science diagnostics. Use it when you need to see how sRGB/Rec.709, Display-P3, and Rec.2020 sit inside the visible locus, how PQ and HLG map signal values into nits, how a sample moves in ICtCp or JzAzBz, and what data should be exported for a design, engineering, or display-calibration handoff.

1. Open the Lab

Tool URL: open HDR Gamut Plot Lab.
Default state: the page opens on Rec.2020 with sRGB/Rec.709, Display-P3, and Rec.2020 overlays enabled, CIE 1931 xy axes, a 1000 nit peak, PQ transfer curve, ICtCp plane, and Reinhard tone mapping.
Zero-network workflow: diagrams, exports, image analysis, and batch conversion run in the browser. Uploaded images are read into a local canvas for analysis.
Keyboard shortcuts: press 1 for gamma 2.2, 2 for gamma 2.4, 3 for PQ, 4 for HLG, and A to switch between xy and u-prime v-prime axes.

2. Workspace Layout

Lab tab: the primary working area. It contains the gamut, axes, and observer controls, the chromaticity diagram, hover sampler, metrics table, and image drop.
Curves tab: peak brightness, tone curve, HLG environment, and signal level controls, the tone-curve canvas, and the EOTF comparison.
Planes tab: the ICtCp or JzAzBz perceptual plane, the tone mapping operator, and the luminance boundary rings.
Data tab: every dataset the tool uses, with its source and a status such as Verbatim, Computed, Stand-in, or Absent.
Export tab: choose what to take and a format, preview the exact file, then download or copy it. It also holds batch hex conversion and a comparison of the three built-in gamuts.
Reference tab: Standards (BT.2020, BT.2100, ST 2084 PQ, ARIB STD-B67 HLG, ICtCp, JzAzBz, BT.709/sRGB, and Display-P3), Formulas, Citations, and Research notes, with one search filter across all four.

3. Gamuts and overlays

Working color space: choose sRGB, P3, or Rec2020. Its triangle is drawn heavier on the chromaticity diagram.
Overlay gamuts: independently show or hide Rec.709/sRGB, Display-P3, and Rec.2020 triangles. The metrics table still computes all built-in spaces.
Spectral locus: draws the approximate CIE 1931 spectral boundary from 380 nm to 700 nm in 5 nm steps.
Line of purples: closes the visible chromaticity boundary between the long-wave and short-wave ends of the spectral locus.
ICtCp marker: the checkbox is disabled; the page says the marker is not drawn yet.
Share of locus: each gamut area is quoted as a share of the CIE 1931 spectral locus, measured in the plane on screen (xy or u-prime v-prime). No built-in gamut is the 100 percent reference.

4. Chromaticity axes and sampling

CIE 1931 xy: the default chromaticity view. It is familiar for standards documentation and primary-coordinate comparison.
CIE 1976 u-prime v-prime: remaps chromaticity to a more perceptually even coordinate plane for spacing comparisons.
Observer selector: the locus is drawn from the CIE 1931 2 degree table whichever observer you choose; the 10 degree table is not in the tool yet.
Hover sampler: move the cursor over the main diagram to see xy or u-prime v-prime coordinates, XYZ, CIELAB L*, and ICtCp I/Ct/Cp for the sampled point.
Axes status: the current axis mode is repeated above the canvas and preserved in the share URL.

5. Peak nits and tone curves

Peak brightness: drag the 100 to 10000 nit slider to set the display or mastering reference for the gamma and HLG tone curves, HLG system gamma, and batch conversion. PQ is absolute and is not scaled by it.
Gamma 2.2 and gamma 2.4: useful for SDR comparison against HDR transfer behavior.
PQ ST 2084: maps normalized signal values to absolute luminance up to 10000 nits. Use it for HDR10-style mastering review.
HLG BT.2100: maps signal values through HLG behavior and applies a system gamma derived from peak luminance and the selected viewing environment.
HLG environment: choose reference dark, dim surround, or bright surround. The displayed gamma_sys value updates with the peak setting.
Signal level: enter a normalized value from 0 to 1. It drives the sample luminance used by the perceptual plane, hover data, and batch conversion.
Tone mapping operator: Reinhard, Hable (Filmic), ACES Filmic, or Uchimura (Gran Turismo) maps the plane's luminance onto the peak brightness, and the plane prints the result: the operator, the mapped luminance in nits and the display peak.

6. ICtCp and JzAzBz planes

ICtCp mode: displays the Ct and Cp chroma axes after BT.2100-style LMS and PQ processing. It is useful for HDR video color-difference reasoning.
JzAzBz mode: displays the Az and Bz axes for a high-dynamic-range perceptual color model designed to behave more consistently at high luminance.
Plane canvas: the Planes tab canvas redraws when you change the color space, overlays, peak, curve, signal level, plot mode, or tone mapping operator.
Interpretation: these plots are diagnostic views, not ICC proofing. Use them to compare model behavior and relative movement, then validate final output with the intended display pipeline.

7. Exports, compare, and share

Gamut JSON: The measurements as JSON gives built-in gamut definitions, primary coordinates, white points, area, share of the spectral locus, and metadata for axes, peak nits, curve type, locus area, observer, and tool name.
CSS variables: The measurements as CSS gives custom properties for each gamut's locus share, area, and RGB primary coordinates, plus the plane, peak nits, and selected curve type.
CSV: The measurements as CSV gives a table with RGB primaries, white point, area, and locus share percentage for sRGB/Rec.709, Display-P3, and Rec.2020. The curve as CSV gives the drawn tone curve as signal and nits.
Export PNG: The diagram, The curve plot, or The plane downloads the chromaticity diagram, tone curve, or perceptual plane as a PNG file.
Share URL: A link to this view copies a URL containing axes, peak, curve, and mode query parameters.
Compare all spaces: the Export tab draws a bar chart and table of each built-in gamut's area and share of the spectral locus for the current axis mode.

8. Research panels

EOTF comparison: on the Curves tab, compares PQ, HLG at 1000 nits, and an SDR gamma curve on a logarithmic luminance scale.
HDR gamut boundary: on the Planes tab, draws ICtCp or JzAzBz boundary rings at 0.1, 1, 10, 100, 500, 1000, 4000, and 10000 nits for visible overlay spaces.
HDR image analysis: in the Lab, drop a PNG or JPEG. It is read into a capped local canvas as sRGB, sampled, and measured for how much of the sRGB, P3, and Rec.2020 triangles its chromaticities occupy. Its pixels are also drawn as dots on the chromaticity diagram, in xy or u-prime v-prime. Nothing is reported in nits.
Batch color conversion: on the Export tab, paste comma-separated or line-separated hex colors into Convert a list, then generate CIELAB, ICtCp, and JzAzBz values using the current signal level and transfer context.
Batch CSV: Download the result downloads hdr-batch-ictcp.csv with columns for Hex, L*, a*, b*, I, Ct, Cp, Jz, Az, and Bz.
Research caution: boundary and image coverage outputs are fast diagnostic estimates. They are not a substitute for full HDR profile management or calibrated measurement hardware.

9. Library saves and restore

Library asset type: HDR Gamut Plot registers as a preset tool in Auric Library.
Snapshot capture: the Library binding captures the first available tool canvas, normally the chromaticity diagram, as an HDR gamut plot asset preview.
Runtime state: full tool-state capture reads the HDR Gamut Plot state through window.AAHdrGamutPlot.getState().
Restore: saved state can restore color space, axes, observer, peak nits, curve, HLG environment, signal level, plot mode, tone mapping operator, and overlay toggles.
Share versus Library: a share URL stores only axes, peak, curve, and perceptual mode. Library state can preserve more of the interactive control state.

10. Recommended workflows

HDR display comparison: keep all overlays enabled, select xy axes, choose Rec.2020, set the target peak, and export the chromaticity PNG plus the measurements CSV.
P3 delivery review: select Display-P3, show Rec.709 and Rec.2020 overlays, compare the tone curve in PQ and HLG, then copy JSON for documentation.
Transfer curve explanation: use keyboard shortcuts 1 through 4 to flip between gamma, PQ, and HLG while watching the tone-curve canvas.
Perceptual model comparison: set signal level to a meaningful code value, flip between ICtCp and JzAzBz, and use the Planes tab boundary rings for luminance-dependent context.
Image triage: upload a still, record how much of each gamut it occupies, then save the resulting state through Library for review history.
Batch palette audit: paste brand or UI colors into Convert a list, copy the CSV, and compare the values against your HDR target curve.

11. Troubleshooting

The diagram looks empty: make sure at least one overlay gamut is enabled and the Spectral locus option is on if you want the visible boundary.
The share URL did not restore every control: the URL stores axes, peak, curve, and perceptual mode only. Use Library state for broader restore coverage.
The observer setting appears unchanged: the current renderer uses the built-in CIE 1931 spectral locus data. Observer is preserved as state and label context.
Image analysis looks approximate: browser image pixels are usually decoded as standard RGB values. The tool reports chromaticity occupancy, not HDR luminance.
Batch colors are ignored: use six-digit hex values such as #ffcc00. Values can be separated by commas or line breaks.
Copy buttons fail: clipboard access may require a secure context or an active user gesture in some browsers.
Exports show the current view only: PNG exports reflect the current canvas state. Update the controls before exporting if you changed tabs or settings.