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[css-color-5] Improve hue-rotate diagram, #7690
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svgeesus committed Sep 5, 2022
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14 changes: 10 additions & 4 deletions css-color-5/Overview.bs
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Expand Up @@ -1161,15 +1161,21 @@ However, unlike HSL, manipulations are not guaranteed to be in-gamut.
which is <span class="swatch" style="--color: rgb(0% 64.2% 66.3%)"></span> rgb(0% 64.2% 66.3%). The difference in chroma (37.5, instead of 90) is huge.

<figure id="fig-LCH-rotation-oog">
<img src="images/LCH-rotation-oog.svg"
width="540" height="520"
alt="Diagram of CH plane showing relative color manipulation">
<object data="images/LCH-rotation-oog.svg"
width="540" height="520"></object>
<p>Diagram of CIE CH plane showing relative color manipulation.
The <em>a</em> and <em>b</em> axes are labelled,
and cross in the middle.
We are looking down the central Lightness axis.
The maximal gamut of the sRGB color space
is shown as an irregular, convex polygon.
</p>
<figcaption>
This diagram shows the sRGB gamut, in the CIE ab plane.
Small circles indicate the primary and secondary color.
The <span class="swatch" style="--color: rgb(86.1% 33.4% 97.6%)"></span>
origin color, shown as a large circle, is in gamut for sRGB;
becomes <span class="swatch oog" style="--color: #AAA"></span> out of gamut (shown as a grey fill and red border)
but becomes <span class="swatch oog" style="--color: #AAA"></span> out of gamut (shown as a grey fill and red border)
when the LCH hue is rotated -120°.
The gamut-mapped <span class="swatch" style="--color: rgb(0% 64.2% 66.3%)"></span> result has much lower chroma.
</figcaption>
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28 changes: 23 additions & 5 deletions css-color-5/images/LCH-rotation-oog.svg
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