Rolling 20210913

code/main/Color.cpp

@@ -0,0 +1,132 @@
+#include "Color.h"
+#include <algorithm>
+#include <cmath>
+#include <cassert>
+
+namespace {
+
+// Int -> fixed point
+int up( int x ) { return x * 255; }
+
+} // namespace
+
+int iRgbSqrt( int num ) {
+    // https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Binary_numeral_system_.28base_2.29
+    assert( "sqrt input should be non-negative" && num >= 0 );
+    assert( "sqrt input should no exceed 16 bits" && num <= 0xFFFF );
+    int res = 0;
+    int bit = 1 << 16;
+    while ( bit > num )
+        bit >>= 2;
+    while ( bit != 0 ) {
+        if ( num >= res + bit ) {
+            num -= res + bit;
+            res = ( res >> 1 ) + bit;
+        } else
+            res >>= 1;
+        bit >>= 2;
+    }
+    return res;
+}
+
+Rgb::Rgb( Hsv y ) {
+    // https://stackoverflow.com/questions/24152553/hsv-to-rgb-and-back-without-floating-point-math-in-python
+    // greyscale
+    if( y.s == 0 ) {
+        r = g = b = y.v;
+        return;
+    }
+
+    const int region = y.h / 43;
+    const int remainder = ( y.h - ( region * 43 ) ) * 6;
+
+    const int p = ( y.v * ( 255 - y.s ) ) >> 8;
+    const int q = ( y.v * ( 255 - ( ( y.s * remainder ) >> 8 ) ) ) >> 8;
+    const int t = ( y.v * ( 255 - ( ( y.s * (255 -remainder ) ) >> 8 ) ) ) >> 8;
+
+    switch( region ) {
+        case 0: r = y.v; g = t; b = p; break;
+        case 1: r = q; g = y.v; b = p; break;
+        case 2: r = p; g = y.v; b = t; break;
+        case 3: r = p; g = q; b = y.v; break;
+        case 4: r = t; g = p; b = y.v; break;
+        case 5: r = y.v; g = p; b = q; break;
+        default: __builtin_trap();
+    }
+
+    a = y.a;
+}
+
+Rgb& Rgb::operator=( Hsv hsv ) {
+    Rgb r{ hsv };
+    swap( r );
+    return *this;
+}
+
+Rgb Rgb::operator+( Rgb in ) const {
+    auto copy = *this;
+    copy += in;
+    return copy;
+}
+
+Rgb& Rgb::operator+=( Rgb in ) {
+    unsigned int red = r + in.r;
+    r = ( red < 255 ) ? red : 255;
+    unsigned int green = g + in.g;
+    g = ( green < 255 ) ? green : 255;
+    unsigned int blue = b + in.b;
+    b = ( blue < 255 ) ? blue : 255;
+    return *this;
+}
+
+Rgb& Rgb::blend( Rgb in ) {
+    unsigned int inAlpha = in.a * ( 255 - a );
+    unsigned int alpha = a + inAlpha;
+    r = iRgbSqrt( ( ( r * r * a ) + ( in.r * in.r * inAlpha ) ) / alpha );
+    g = iRgbSqrt( ( ( g * g * a ) + ( in.g * in.g * inAlpha ) ) / alpha );
+    b = iRgbSqrt( ( ( b * b * a ) + ( in.b * in.b * inAlpha ) ) / alpha );
+    a = alpha;
+    return *this;
+}
+
+uint8_t IRAM_ATTR Rgb::getGrb( int idx ) {
+    switch ( idx ) {
+        case 0: return g;
+        case 1: return r;
+        case 2: return b;
+    }
+    __builtin_unreachable();
+}
+
+Hsv::Hsv( Rgb r ) {
+    int min = std::min( r.r, std::min( r.g, r.b ) );
+    int max = std::max( r.r, std::max( r.g, r.b ) );
+    int chroma = max - min;
+
+    v = max;
+    if ( chroma == 0 ) {
+        h = s = 0;
+        return;
+    }
+
+    s = up( chroma ) / max;
+    int hh;
+    if ( max == r.r )
+        hh = ( up( int( r.g ) - int( r.b ) ) ) / chroma / 6;
+    else if ( max == r.g )
+        hh = 255 / 3 + ( up( int( r.b ) - int( r.r ) ) ) / chroma / 6;
+    else
+        hh = 2 * 255 / 3 + ( up( int( r.r ) - int( r.g ) ) ) / chroma / 6;
+
+    if ( hh < 0 )
+        hh += 255;
+    h = hh;
+
+    a = r.a;
+}
+
+Hsv& Hsv::operator=( Rgb rgb ) {
+    Hsv h{ rgb };
+    swap( h );
+    return *this;
+}