[hue] Improve color setting

[andrewfg]

There are three issues..

1) Hue bulb changing color wrongly when brightness is 0

As reported on the forum here if OH sends an HSBType color command, where B is 0, it causes the wrong color value to be set on the lamp.

The reason is that the ColorUtil.hsbToXy() method produces, for the special case where B is 0, an xy color co-ordinate of [0,0] which is outside the color gamut of any physical lamp; and this (wrongly) causes the gamut correction to convert that [0,0] value to the closest xy color co-ordinate within the actual lamp's color gamut i.e. namely it sets the lamp to its gamut:blue color.

2) Use same color Gamut as Hue App

See this #16482

3) RGB gamma correction is inconsistently applied

See core #4102

When the binding sends a color XY command to the bridge, it applies a variable gamma correction depending on the dimming level of the lamp. Whereas when the bridge sends an XY state update to the binding, it applies a fixed reverse gamma correction that does not depend on the dimming level. This means that the round trip HSB => xy => bridge => xy => HSB has inconsistent results particularly at low brightness levels.

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This PR fixes all these issues (resolves #16482). (Plus some modernizations of instanceof syntax).

The Jar file in Zip form is here

Signed-off-by: Andrew Fiddian-Green software@whitebear.ch

[andrewfg]

See also openhab/openhab-core#4124

[openhab-bot]

This pull request has been mentioned on openHAB Community. There might be relevant details there:

https://community.openhab.org/t/hue-bulb-changing-color-wrongly-when-brightness-is-0/154005/18

[andrewfg]

Changed to WIP pending #16482

[andrewfg]

@jlaur we seem to have reached a consensus on #16482 so I will update this PR to include those changes, and mark it again as ready for review..

[openhab-bot]

This pull request has been mentioned on openHAB Community. There might be relevant details there:

https://community.openhab.org/t/hue-bulb-changing-color-wrongly-when-brightness-is-0/154005/26

[andrewfg]

See this https://community.openhab.org/t/hue-bulb-changing-color-wrongly-when-brightness-is-0/154005/28?u=andrewfg

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EDIT: I am wondering if the xy should be constructed from an HSB with a fixed B? reason is that the dimmer data is anyway separately transmitted on a different DTO..

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EDIT 2: to answer my own question: it should not use a fixed B. Reason is that the Gamma Correction needs to be applied. However I think there may be another bug in the Hue binding whereby reverse gamma correction is being omitted. I will check it..

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EDIT 3: it’s 4:30 AM and I had an epiphany. Marking this now as WIP again..

[andrewfg]

Ok. I have now also fixed the gamma round trip issue. Ready to go again. :)

[openhab-bot]

This pull request has been mentioned on openHAB Community. There might be relevant details there:

https://community.openhab.org/t/hue-bulb-changing-color-wrongly-when-brightness-is-0/154005/31

[jlaur]

Only minor comment from my side to remove "TODO" code smells.

Is it correct that this PR no longer has any direct relation to openhab/openhab-core#4124 (besides the tests that might be affected), but completely independently fixes issues in the binding that would have to be fixed the same way with or without openhab/openhab-core#4124?

@kaikreuzer - would you like to complete your review after the latest changes and simplifications?

[andrewfg]

Is it correct that this PR no longer has any direct relation to openhab/openhab-core#4124 (besides the tests that might be affected), but completely independently fixes issues in the binding that would have to be fixed the same way with or without openhab/openhab-core#4124?

Correct.

• This PR works with both ColorUtil versions before and after ColorUtil bug fixes and improvements openhab-core#4124 and improves the precision of color setting in both cases.
• The core ColorUtil bug fixes and improvements openhab-core#4124 PR adds further improvements in color precision on HSB => xy => HSB round trips, as well as eliminating edge case errors, and bugs in RGB <=> RGBW conversions.

[andrewfg]

@kaikreuzer I believe that @jlaur is deferring until you complete your own review of this. So in order to make progress, I wonder if there is any further information that you need from my side, in order to help that?

[kaikreuzer]

@kaikreuzer - would you like to complete your review after the latest changes and simplifications?

@jlaur All fine for me; so feel free to merge if you are fine with it as well.

[jlaur]

LGTM