dynamically set home assistant led brightness for higher dynamic range

[redstefan1]

Feature request

Make it so that instead of the user manually having to set a brightness value in the configuration, hyperion calculates a good brightness value for each update

What problem does this feature solve?

Currently, it is very hard to get colors looking right in the home assistant output. The fact that every color is always being sent with the same brightness limits the dynamic range drastically and causes the effect to be very mediocre. For example having the brightness be set quite high (like the default) makes it look great in well lit scenes or situations in which a large amount of light is required (think explosions, fire, and the like) but makes it look terrible in dimly lit scenes, and vice versa.

Another issue this might fix is that for homeassistant lights which support both rgb color mode and temperature adjustable white light, having the brightness be high but also sending color values close to black but not quite there yet can make the light go out of color mode and instead start emitting white light.
(I know that the current implementation tries to work around this by turning the light off when it is black but it is still quite common for me to run into this and get flashbanged)

What does the proposed API look like?

In the current implementation every api request contains a color value and (optionally) a fixed brightness value, I propose replacing the fixed brightness value with some calculated brightness value based on the rgb value (eg. higher values = more brightness and the other way around).

How should this be implemented in your opinion?

find some mathematical function to calculate the perceived brightness of any rgb value and implement it as stated above.

Are you willing to work on this yourself?

yes absolutely, am just kind of unsure about my coding skills since I honestly suck at coding but this seems like something fun I'd like to try out

[Lord-Grey]

Thanks for your suggestion.

You might check, if the luminance formula from the Rec. 709 (or BT.709) is what you are looking for.

I did am update to the HA write function to apply the same, if brightness is not to be overwritten.
Maybe you can try, if that works for you.

int LedDeviceHomeAssistant::write(const QVector<ColorRgb>& ledValues)
{
	QJsonObject serviceAttributes{ {ENTITY_ID, QJsonArray::fromStringList(_lightEntityIds)} };
	ColorRgb ledValue = ledValues.at(0);

	//    http://hostname:port/api/services/light/turn_on
	//    {
	//      "entity_id": [ entity-IDs ],
	//      "rgb_color": [R,G,B]
	//    }

	_restApi->setPath(API_LIGHT_TURN_ON);
	serviceAttributes.insert(RGB_COLOR, QJsonArray{ ledValue.red, ledValue.green, ledValue.blue });

	int brightness;
	if (!_isBrightnessOverwrite)
	{
		brightness = qBound(0, qRound(0.2126 * ledValue.red + 0.7152 * ledValue.green + 0.0722 * ledValue.blue), 255);
	}
	else
	{
		brightness = _brightness;
	}

	serviceAttributes.insert(BRIGHTNESS, brightness);

	if (_transitionTime > 0)
	{
		serviceAttributes.insert(TRANSITION, _transitionTime);
	}

	httpResponse response = _restApi->post(serviceAttributes);
	if (response.error())
	{
		Warning(_log, "Updating lights failed with error: '%s'", QSTRING_CSTR(response.getErrorReason()));
		return -1;
	}

	return 0;
}

You could check the following commit: Lord-Grey@e153354

[redstefan1]

Sorry for not answering in a while, stuff has been kinda busy last week.

Yea this kind of function is exactly what I mean, should get to testing it soon

[SophiaH67]

Want to chime in and say, @Lord-Grey thanks so much for that patch! I applied it to my local instance and it works SO well. Amazing job!! ❤️