Hi, is it possible to define a gradient Palette at runtime?  the DEFINE_GRADIENT_PALETTE uses the

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Hi,

is it possible to define a gradient Palette at runtime?

the DEFINE_GRADIENT_PALETTE uses the program memory.

In my situation I want to create a new Palette each frame dynamically, it is for a christmas candle effect where the gradient points are “candles” that change their brigntness based on an algorithm from here http://bienonline.magix.net/public/avr-advent.html (its german, but google translate is ok) and I want brigntness gradients between those virtual candles along a strip of 200 LEDs which I use as an indirect lighting in my living room. It shall give an effect to the room that it is lighted by a lot of flickering candles.

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Yes, note the SetupXXXPalette functions in the ColorPalette example: https://github.com/FastLED/FastLED/blob/master/examples/ColorPalette/ColorPalette.ino

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To my understanding those SetupXXXPalette functions create CRGBPalette16 objects, where 16 colors have an equal “distance” in the palette, while the gradient palettes define also the control points of the gradients. Sure, I can achieve something with the 16 element palettes but I have plenty of RAM so it would be nice to have the gradient function.

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Yep, you can do this. Internally, all palettes are CRGBPalette16 (or 256), even the ones defined as a gradient – the gradient is just a convenient and compact way to define them.

So. You want this:

CRGBPalette16 myPal16;
myPal16.loadDynamicGradientPalette( dynPalDef);

That will load a gradient palette from ‘dynPalDef’ into the CRGBPalette16 named myPal16.

dynPalDef should just be an array of bytes in exactly the same format that you feed into DEFINE_GRADIENT_PALETTE:

index1, R1, G1, B1,
index2, R2, G2, B2,
index3, R3, G3, B3,
(etc until indexN == 255)

There’s no example code for this, but it is possible and it works. Set up a byte array with the gradient palette definition, create a CRGBPalette16, and then call myPal16.loadDynamicGradientPalette. Then use myPal16 as usual.

When you get it working, share your code here – other people might want to see it!

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great - it works - thank you very much!

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For anybody curious, this is how I implemented this

typedef unsigned char byte;

byte bytes[8];

bytes[0] = 0;
bytes[1] = 255;
bytes[2] = 0;
bytes[3] = 0;

bytes[4] = 255;
bytes[5] = 0;
bytes[6] = 0;
bytes[7] = 255;

currentpalette.loadDynamicGradientPalette(bytes);

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This is gold. I was trying to find a way to change the palette at runtime as well, as I have a web app that sends a request to my esp2866 server with the palette… so the palette can be created in the web app with a color picker.

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Hello @twofingerrightclick

Glad you found a nugget! This is the FastLED G+ archives. Please visit our Reddit group for current discussions.

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