I have been unsatisfied with the available gamut mapping in LightSys IV,
in part because the violet in a gamut-mapped spectrum is too bright.
But when I preserve the luminance (gray level) of the gamut-mapped
spectrum colors, the violet is so dark it is barely visible.  I have
worked out a compromise, which will be available in the next update of
spectrum.inc in the Object Collection.

Meanwhile, earlier this year I discovered adding a little bit of gray to
the luminance-mapped spectrum really brings out the violet.

In gray+spectrum.png, the leftmost spectrum preserves the luminosity of
the color, while the rightmost spectrum has sufficient gray added such
that no gamut mapping at all is needed.  The intermediate spectra have
increasing amounts of gray added, from left to right.  The "sat." figure
shows the saturation of the most saturated color of each spectrum; any
spectrum with a figure greater than 1 has colors that are outside the
sRGB gamut.

Image gm-methods.png is a comparison of gamut mapping methods.

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Preview of image 'gm-methods.png'