Cubehelix_color_MaxMSP/Cubehelix.js

// Cubehelix color scheme for Max/MSP/Jitter
// By Théophile Clet
// https://tflcl.xyz
//
// Based on Dave Green's work:
// http://www.mrao.cam.ac.uk/~dag/CUBEHELIX/cubetry.html
//
// Original publication: Green, D. A., 2011, `A colour scheme for the display of astronomical intensity images', Bulletin of the Astronomical Society of India, 39, 289. (2011BASI...39..289G at ADS.)
// http://astron-soc.in/bulletin/11June/289392011.pdf )
//
// Original js code taken straight from the online example implementation:
// http://www.mrao.cam.ac.uk/~dag/CUBEHELIX/cubetry.html


autowatch = 0;
inlets = 1;
outlets = 4;

var RGBOUTLET = 0;
var HSLOUTLET = 1;
var LISTOUTLET = 2
var DUMPOUTLET = 3;

setinletassist(0, "List as input: {makeCubehelixRGB, start[float], rots[float], sign[-1,1], hue[float], gamma[float], levels(int), flip([0,1]}")
setoutletassist(0, "To jit.matrix: always outputs the color palette as a ARGB 4-plane matrix");
setoutletassist(1, "To jit.matrix: if 'hslenable 1' outputs the color palette as a AHSL 4-plane matrix");
setoutletassist(2, "If 'listmode 1' outputs all colors in list format as RGB or HSL.");
setoutletassist(3, "Bangs when generation is done.");

var hslmode = false;
var listmode = false;

function hslenable(s){
  hslmode = s;
}
function listenable(s){
  listmode = s;
}

function makeCubehelix(start, rots, hue, gamma, levels, flip){

  //dumpOut(start, rots, hue, gamma, levels, flip);
  outlet(RGBOUTLET, "dim", levels, 1);
  if (hslmode) {
    outlet(HSLOUTLET, "dim", levels, 1);
  }


  for (var i = 0; i < levels; i++) {


    var fract = CubeHelixFract(i,levels,flip);
    var color = CubeHelixRGB(fract,start,rots,hue,gamma);


    if(flip == 1){fract = 1.0-fract;}

    outlet(RGBOUTLET, "setcell", i, 0, "val", 1., color);

    if (hslmode) {
      color = rgb2hsl(color[0], color[1], color[2]);
      outlet(HSLOUTLET, "setcell", i, 0, "val", 1., color);
    }

    if (listmode) { outlet(LISTOUTLET, i, color); }

  }

  outlet(RGBOUTLET, "bang");
  if (hslmode) { outlet(HSLOUTLET, "bang"); }
  if (listmode) { outlet(LISTOUTLET, "bang"); }

  outlet(DUMPOUTLET, "bang");
}

function dumpOut(start, rots, hue, gamma, levels, flip){
  outlet(DUMPOUTLET, "start", start);
  outlet(DUMPOUTLET, "rots", rots);
  outlet(DUMPOUTLET, "hue", hue);
  outlet(DUMPOUTLET, "gamma", gamma);
  outlet(DUMPOUTLET, "levels", levels);
  outlet(DUMPOUTLET, "flip", flip);
}

function rgb2hsl(r,g,b) {
  var max = Math.max(r, g, b), min = Math.min(r, g, b);
  var h, s, l = (max + min) / 2;

  if (max == min) {
    h = s = 0; // achromatic
  } else {
    var d = max - min;
    s = l > 0.5 ? d / (2 - max - min) : d / (max + min);

    switch (max) {
      case r: h = (g - b) / d + (g < b ? 6 : 0); break;
      case g: h = (b - r) / d + 2; break;
      case b: h = (r - g) / d + 4; break;
    }

    h /= 6;
  }

  return [ h, s, l ];
}
// ----------------------------------------------------------------------------
// 2017 May 30: make consistent with Fortran
// 2021 mai 12:  a bit of calculation optimization (I think) - Théophile Clet
// ----------------------------------------------------------------------------

function CubeHelixRGB(fract,start,rots,hue,gamma){

    var angle = 2*Math.PI*(start/3.0+1+rots*fract);
    var fract = Math.pow(fract, gamma);
    var amp=hue*fract*(1-fract)/2.0;
    var acos = Math.cos(angle);
    var asin = Math.sin(angle);

    var r=fract+amp*(-0.14861*acos+1.78277*asin);
    r=Math.max(Math.min(r,1.0),0.0);

    var g=fract+amp*(-0.29227*acos-0.90649*asin);
    g=Math.max(Math.min(g,1.0),0.0);

    var b=fract+amp*(+1.97294*acos);
    b=Math.max(Math.min(b,1.0),0.0);

    return [r, g, b];
}

// ----------------------------------------------------------------------------

function CubeHelixFract(i,n,flip){
    var fraction = i/(n-1);
    if (flip == 1) {
      fraction = 1 - fraction;
    }
    return fraction;
}