init_binary_dithering()

template<EOrder RGB_ORDER, int LANES = 1, uint32_t MASK = 0xFFFFFFFF>

void PixelController< RGB_ORDER, LANES, MASK >::init_binary_dithering ( )

inline

Set up the values for binary dithering.

Definition at line 238 of file pixel_controller.h.

                                 {
#if !defined(NO_DITHERING) || (NO_DITHERING != 1)
        // R is the digther signal 'counter'.
        static uint8_t R = 0;
        ++R;
 
        // R is wrapped around at 2^ditherBits,
        // so if ditherBits is 2, R will cycle through (0,1,2,3)
        uint8_t ditherBits = VIRTUAL_BITS;
        R &= (0x01 << ditherBits) - 1;
 
        // Q is the "unscaled dither signal" itself.
        // It's initialized to the reversed bits of R.
        // If 'ditherBits' is 2, Q here will cycle through (0,128,64,192)
        uint8_t Q = 0;
 
        // Reverse bits in a byte
        {
            if(R & 0x01) { Q |= 0x80; }
            if(R & 0x02) { Q |= 0x40; }
            if(R & 0x04) { Q |= 0x20; }
            if(R & 0x08) { Q |= 0x10; }
            if(R & 0x10) { Q |= 0x08; }
            if(R & 0x20) { Q |= 0x04; }
            if(R & 0x40) { Q |= 0x02; }
            if(R & 0x80) { Q |= 0x01; }
        }
 
        // Now we adjust Q to fall in the center of each range,
        // instead of at the start of the range.
        // If ditherBits is 2, Q will be (0, 128, 64, 192) at first,
        // and this adjustment makes it (31, 159, 95, 223).
        if( ditherBits < 8) {
            Q += 0x01 << (7 - ditherBits);
        }
 
        // D and E form the "scaled dither signal"
        // which is added to pixel values to affect the
        // actual dithering.
 
        // Setup the initial D and E values
        for(int i = 0; i < 3; ++i) {
                uint8_t s = mColorAdjustment.premixed.raw[i];
                e[i] = s ? (256/s) + 1 : 0;
                d[i] = scale8(Q, e[i]);
#if (FASTLED_SCALE8_FIXED == 1)
                if(d[i]) (--d[i]);
#endif
                if(e[i]) --e[i];
        }
#endif
    }

References d, e, mColorAdjustment, scale8(), and VIRTUAL_BITS.

Referenced by enable_dithering().

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