FastLed 2.1 - added saturation to ColorFromPalette (colorutils.cpp)

colorutils

/* use this code in Arduino
  for (int i=0; i <NUM_LEDS; i++)
  { leds[i] = ColorFromPalette( currentPalette, map(i, 0, NUM_LEDS, 0, 255), brightness, map(i, 0, NUM_LEDS, 0, 255));
  }
*/

// blend doesn't seem to be implemented/necessary in CRGBPalette, so I left it out
// Probably this can be optimized? See questions in comments. 

CRGB ColorFromPalette( const CRGBPalette256& pal, uint8_t index, uint8_t brightness, uint8_t saturation)
{
    const CRGB* entry = &(pal[0]) + index;

    uint8_t red   = entry->red;
    uint8_t green = entry->green;
    uint8_t blue  = entry->blue;

        // added manipulation of saturation
        // variables need to become externally accessible
        // just for testing
        uint8_t maxSaturation = 255;
        uint8_t minSaturation = 0;

        // scale saturation in the right range. 
        // and inverse the value (255-saturation)
        saturation = lerp8by8(255 - maxSaturation, 255 - minSaturation, 255 - saturation);
        
        // make saturation appear linear
        // I picked now raw, since we we won't have issues like with dimming brightness:
        // https://plus.google.com/112889495015752015404/posts/UGXWJtFvz61
        saturation = dim8_raw(saturation);

        // apply saturation
        // qadd8 works faster? Because we just add saturation
        red    = lerp8by8(red  , 255, saturation);
        green  = lerp8by8(green, 255, saturation);
        blue   = lerp8by8(blue , 255, saturation);




    if( brightness != 255) {
        nscale8x3_video( red, green, blue, brightness);
    }
    
    return CRGB( red, green, blue);
}