ColorFromPalette() [6/8]

CRGB ColorFromPalette	(	const CRGBPalette32 &	pal,
		uint8_t	index,
		uint8_t	brightness = 255,
		TBlendType	blendType = LINEARBLEND )

Get a color from a palette.

These are the main functions for getting and using palette colors. Regardless of the number of entries in the base palette, this function will interpolate between entries to turn the discrete colors into a smooth gradient.

Parameters

pal	the palette to retrieve the color from
index	the position in the palette to retrieve the color for (0-255)
brightness	optional brightness value to scale the resulting color
blendType	whether to take the palette entries directly (NOBLEND) or blend linearly between palette entries (LINEARBLEND)

Definition at line 862 of file colorutils.cpp.

{
   if ( blendType == LINEARBLEND_NOWRAP) {
     index = map8(index, 0, 247);  // Blend range is affected by lo3 blend of values, remap to avoid wrapping
   }
 
    uint8_t hi5 = index;
#if defined(__AVR__)
    hi5 /= 2;
    hi5 /= 2;
    hi5 /= 2;
#else
    hi5 >>= 3;
#endif
    uint8_t lo3 = index & 0x07;
    
    // const CRGB* entry = &(pal[0]) + hi5;
    // since hi5 is always 0..31, hi4 * sizeof(CRGB) can be a single-byte value,
    // instead of the two byte 'int' that avr-gcc defaults to.
    // So, we multiply hi5 X sizeof(CRGB), giving hi5XsizeofCRGB;
    uint8_t hi5XsizeofCRGB = hi5 * sizeof(CRGB);
    // We then add that to a base array pointer.
    const CRGB* entry = (CRGB*)( (uint8_t*)(&(pal[0])) + hi5XsizeofCRGB);
    
    uint8_t red1   = entry->red;
    uint8_t green1 = entry->green;
    uint8_t blue1  = entry->blue;
    
    uint8_t blend = lo3 && (blendType != NOBLEND);
    
    if( blend ) {
        
        if( hi5 == 31 ) {
            entry = &(pal[0]);
        } else {
            ++entry;
        }
        
        uint8_t f2 = lo3 << 5;
        uint8_t f1 = 255 - f2;
        
        uint8_t red2   = entry->red;
        red1   = scale8_LEAVING_R1_DIRTY( red1,   f1);
        red2   = scale8_LEAVING_R1_DIRTY( red2,   f2);
        red1   += red2;
        
        uint8_t green2 = entry->green;
        green1 = scale8_LEAVING_R1_DIRTY( green1, f1);
        green2 = scale8_LEAVING_R1_DIRTY( green2, f2);
        green1 += green2;
        
        uint8_t blue2  = entry->blue;
        blue1  = scale8_LEAVING_R1_DIRTY( blue1,  f1);
        blue2  = scale8_LEAVING_R1_DIRTY( blue2,  f2);
        blue1  += blue2;
 
        cleanup_R1();
        
    }
    
    if( brightness != 255) {
        if( brightness ) {
            ++brightness; // adjust for rounding
            // Now, since brightness is nonzero, we don't need the full scale8_video logic;
            // we can just to scale8 and then add one (unless scale8 fixed) to all nonzero inputs.
            if( red1 )   {
                red1 = scale8_LEAVING_R1_DIRTY( red1, brightness);
#if !(FASTLED_SCALE8_FIXED==1)
                ++red1;
#endif
            }
            if( green1 ) {
                green1 = scale8_LEAVING_R1_DIRTY( green1, brightness);
#if !(FASTLED_SCALE8_FIXED==1)
                ++green1;
#endif
            }
            if( blue1 )  {
                blue1 = scale8_LEAVING_R1_DIRTY( blue1, brightness);
#if !(FASTLED_SCALE8_FIXED==1)
                ++blue1;
#endif
            }
            cleanup_R1();
        } else {
            red1 = 0;
            green1 = 0;
            blue1 = 0;
        }
    }
    
    return CRGB( red1, green1, blue1);
}

References blend(), brightness, cleanup_R1(), LINEARBLEND_NOWRAP, map8(), NOBLEND, and scale8_LEAVING_R1_DIRTY().

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