hsv2rgb_rainbow() [2/3]

void hsv2rgb_rainbow	(	const CHSV &	hsv,
		CRGB &	rgb )

Definition at line 269 of file hsv2rgb.cpp.hpp.

             {
    // Yellow has a higher inherent brightness than
    // any other color; 'pure' yellow is perceived to
    // be 93% as bright as white.  In order to make
    // yellow appear the correct relative brightness,
    // it has to be rendered brighter than all other
    // colors.
    // Level Y1 is a moderate boost, the default.
    // Level Y2 is a strong boost.
    const fl::u8 Y1 = 1;
    const fl::u8 Y2 = 0;
 
    // G2: Whether to divide all greens by two.
    // Depends GREATLY on your particular LEDs
    const fl::u8 G2 = 0;
 
    // Gscale: what to scale green down by.
    // Depends GREATLY on your particular LEDs
    const fl::u8 Gscale = 0;
 
 
    fl::u8 hue = hsv.hue;
    fl::u8 sat = hsv.sat;
    fl::u8 val = hsv.val;
 
    fl::u8 offset = hue & 0x1F; // 0..31
 
    // offset8 = offset * 8
    fl::u8 offset8 = offset;
    {
#if defined(FL_IS_AVR)
        // Left to its own devices, gcc turns "x <<= 3" into a loop
        // It's much faster and smaller to just do three single-bit shifts
        // So this business is to force that.
        offset8 <<= 1;
        asm volatile("");
        offset8 <<= 1;
        asm volatile("");
        offset8 <<= 1;
#else
        // On ARM and other non-AVR platforms, we just shift 3.
        offset8 <<= 3;
#endif
    }
 
    fl::u8 third = scale8( offset8, (256 / 3)); // max = 85
 
    fl::u8 r, g, b;
 
    if( ! (hue & 0x80) ) {
        // 0XX
        if( ! (hue & 0x40) ) {
            // 00X
            //section 0-1
            if( ! (hue & 0x20) ) {
                // 000
                //case 0: // R -> O
                r = K255 - third;
                g = third;
                b = 0;
                FORCE_REFERENCE(b);
            } else {
                // 001
                //case 1: // O -> Y
                if( Y1 ) {
                    r = K171;
                    g = K85 + third ;
                    b = 0;
                    FORCE_REFERENCE(b);
                }
                if( Y2 ) {
                    r = K170 + third;
                    //uint8_t twothirds = (third << 1);
                    fl::u8 twothirds = scale8( offset8, ((256 * 2) / 3)); // max=170
                    g = K85 + twothirds;
                    b = 0;
                    FORCE_REFERENCE(b);
                }
            }
        } else {
            //01X
            // section 2-3
            if( !  (hue & 0x20) ) {
                // 010
                //case 2: // Y -> G
                if( Y1 ) {
                    //uint8_t twothirds = (third << 1);
                    fl::u8 twothirds = scale8( offset8, ((256 * 2) / 3)); // max=170
                    r = K171 - twothirds;
                    g = K170 + third;
                    b = 0;
                    FORCE_REFERENCE(b);
                }
                if( Y2 ) {
                    r = K255 - offset8;
                    g = K255;
                    b = 0;
                    FORCE_REFERENCE(b);
                }
            } else {
                // 011
                // case 3: // G -> A
                r = 0;
                FORCE_REFERENCE(r);
                g = K255 - third;
                b = third;
            }
        }
    } else {
        // section 4-7
        // 1XX
        if( ! (hue & 0x40) ) {
            // 10X
            if( ! ( hue & 0x20) ) {
                // 100
                //case 4: // A -> B
                r = 0;
                FORCE_REFERENCE(r);
                //uint8_t twothirds = (third << 1);
                fl::u8 twothirds = scale8( offset8, ((256 * 2) / 3)); // max=170
                g = K171 - twothirds; //K170?
                b = K85  + twothirds;
 
            } else {
                // 101
                //case 5: // B -> P
                r = third;
                g = 0;
                FORCE_REFERENCE(g);
                b = K255 - third;
 
            }
        } else {
            if( !  (hue & 0x20)  ) {
                // 110
                //case 6: // P -- K
                r = K85 + third;
                g = 0;
                FORCE_REFERENCE(g);
                b = K171 - third;
 
            } else {
                // 111
                //case 7: // K -> R
                r = K170 + third;
                g = 0;
                FORCE_REFERENCE(g);
                b = K85 - third;
 
            }
        }
    }
 
    // This is one of the good places to scale the green down,
    // although the client can scale green down as well.
    if( G2 ) g = g >> 1;
    // Deliberately the cleaning variant. The _LEAVING_R1_DIRTY form only pays
    // off when several calls are batched before one cleanup_R1(), and this is a
    // lone call whose dirty R1 outlives it on three separate paths: sat == 255
    // and val == 255 both skip their blocks entirely, and the sat == 0 branch
    // below just assigns 255s. Any of those returns to the caller with AVR's
    // __zero_reg__ non-zero. See issue #668.
    if( Gscale ) g = scale8_video( g, Gscale);
 
    // Scale down colors if we're desaturated at all
    // and add the brightness_floor to r, g, and b.
    if( sat != 255 ) {
        if( sat == 0) {
            r = 255; b = 255; g = 255;
        } else {
            fl::u8 desat = 255 - sat;
            desat = scale8_video( desat, desat);
 
            fl::u8 satscale = 255 - desat;
            //satscale = sat; // uncomment to revert to pre-2021 saturation behavior
 
            //nscale8x3_video( r, g, b, sat);
#if (FASTLED_SCALE8_FIXED==1)
            r = scale8_LEAVING_R1_DIRTY( r, satscale);
            asm volatile("");  // Fixes jumping red pixel: https://github.com/FastLED/FastLED/pull/943
            g = scale8_LEAVING_R1_DIRTY( g, satscale);
            asm volatile("");
            b = scale8_LEAVING_R1_DIRTY( b, satscale);
            asm volatile("");
            cleanup_R1();
#else
            if( r ) r = scale8( r, satscale) + 1;
            if( g ) g = scale8( g, satscale) + 1;
            if( b ) b = scale8( b, satscale) + 1;
#endif
            fl::u8 brightness_floor = desat;
            r += brightness_floor;
            g += brightness_floor;
            b += brightness_floor;
        }
    }
 
    // Now scale everything down if we're at value < 255.
    if( val != 255 ) {
 
        // This call is followed by branching before any other scale8 batch,
        // so use the cleaning form rather than carrying dirty R1 through C++.
        val = scale8_video( val, val);
        if( val == 0 ) {
            r=0; g=0; b=0;
        } else {
            // nscale8x3_video( r, g, b, val);
#if (FASTLED_SCALE8_FIXED==1)
            r = scale8_LEAVING_R1_DIRTY( r, val);
            asm volatile("");  // Fixes jumping red pixel: https://github.com/FastLED/FastLED/pull/943
            g = scale8_LEAVING_R1_DIRTY( g, val);
            asm volatile("");
            b = scale8_LEAVING_R1_DIRTY( b, val);
            asm volatile("");
            cleanup_R1();
#else
            if( r ) r = scale8( r, val) + 1;
            if( g ) g = scale8( g, val) + 1;
            if( b ) b = scale8( b, val) + 1;
#endif
        }
    }
 
    // Here we have the old AVR "missing std X+n" problem again
    // It turns out that fixing it winds up costing more than
    // not fixing it.
    // To paraphrase Dr Bronner, profile! profile! profile!
    //asm volatile(  ""  :  :  : "r26", "r27" );
    //asm volatile (" movw r30, r26 \n" : : : "r30", "r31");
    rgb.r = r;
    rgb.g = g;
    rgb.b = b;
}

References FL_NO_EXCEPT, FORCE_REFERENCE, hue, and offset().

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