Is there a way to read the CHSV val parameter from the leds[x] array?

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1

Is there a way to read the CHSV val parameter from the leds[x] array?

I’m working on some code right now to sense when for example, using
fadeToBlackBy( leds, NUM_LEDS, 10);

would get to the last step before becoming completely black. So I figure I’m looking to see when the val parameter is >0 and <10. Is there a way to do this?

2

For that particular case, try
k = leds[i].getAverageLight();

It returns the average of R G and B, and works well for what you’re describing. (And is very fast, unlike RGB-to-HSV approximation.)

3

Not really - there’s a function to convert from RGB back to HSV, but it’s only an approximation. However, for what you specifically want to do here, calling getLuma might give you want you want:

http://fastled.io/docs/3.1/struct_c_r_g_b.html#abd395f8a00bd4f9539f04200df1975f4

4

The idea is to create an effect where when the light is about to fade it “pops” a white flash. So while using FadeToBlackBy() I want to detect the last moment it’s still lit, but not off (because I don’t want to trigger non-active pixels with the effect).

I take it the fade function basically reduces the rgb values by a certain amount until the average is, for example, >1 and <10 and this would work?

Assuming leds[i].getAverageLight() is what to use, what’s the most efficient way to match it being >0 and <x? Should I resolve the value to a uint8_t variable and then do the compare, or reference the function twice in an if statement? I’m really anal about trying to write fast and memory efficient code.

5

The fade function multiplies each r g and b channel by ((255-fadeamount)/256).

So if fade amount is “10”, the each channel is multiplied by ((255-10)/256), or 0.957.

So if the Red channel for a pixel was, say, 50 beforehand, it would be 47 afterwards.

You can calculate from your fade amount number what will happen.

But mostly: just try it and see what you like visually!