fill_gradient with palette support

colorutils.h

// Fill an array of colors with a sixteen-stop gradient from a palette.
// Only suitable for really long fades where banding must be minimised.
template <typename T>
void fill_gradient( T* targetArray, uint16_t numLeds,
                    const CHSVPalette16& palette,
                    TGradientDirectionCode directionCode = SHORTEST_HUES )
{
    uint16_t spanLength = (numLeds / 15);
	
    for (uint8_t spanIdx = 0; spanIdx < 14; spanIdx++)
    {
        uint16_t spanStart = spanIdx * spanLength;
        uint16_t spanEnd = (spanIdx+1) * spanLength;
        fill_gradient(targetArray, spanStart, palette.entries[spanIdx], spanEnd, palette.entries[spanIdx+1], directionCode);
    }

    // The 15th span includes any leftover pixels from division
    uint16_t spanStart = 14 * spanLength;
    uint16_t spanEnd = numLeds - 1;
    fill_gradient(targetArray, spanStart, palette.entries[14], spanEnd, palette.entries[15], directionCode);
}

// convenience synonym
#define fill_gradient_HSV fill_gradient

// etc...