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Cubehelix.js

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+// 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 = 2;
+
+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: outputs the color palette as a 4-plane 1 dim matrix");
+setoutletassist(1, "dump out. Outputs paramters used for generation. Bangs when finished.");
+
+function makeCubehelixRGB(start, rots, sign, hue, gamma, levels, flip){
+  rots = rots*sign;
+
+  //dumpOut(start, rots, hue, gamma, levels, flip);
+
+  outlet(0, "dim", levels, 1);
+  for (var i = 0; i < levels; i++) {
+
+    var fract = CubeHelixFract(i,levels,flip);
+    var red = CubeHelixRGB(fract,start,rots,hue,gamma,1);
+    var grn = CubeHelixRGB(fract,start,rots,hue,gamma,2);
+    var blu = CubeHelixRGB(fract,start,rots,hue,gamma,3);
+
+    if(flip == 1){fract = 1.0-fract;}
+
+    outlet(0, "setcell", i, 0, "val", 1., red, grn, blu);
+  }
+  outlet(0, "bang");
+  outlet(1, "bang");
+}
+
+function dumpOut(start, rots, hue, gamma, levels, flip){
+  outlet(1, "start", start);
+  outlet(1, "rots", rots);
+  outlet(1, "hue", hue);
+  outlet(1, "gamma", gamma);
+  outlet(1, "levels", levels);
+  outlet(1, "flip", flip);
+}
+// ----------------------------------------------------------------------------
+// 2017 May 30: make consistent with Fortran
+// ----------------------------------------------------------------------------
+
+function CubeHelixRGB(fract,start,rots,hue,gamma,irgb){
+
+    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 r=fract+amp*(-0.14861*Math.cos(angle)+1.78277*Math.sin(angle));
+    var g=fract+amp*(-0.29227*Math.cos(angle)-0.90649*Math.sin(angle));
+    var b=fract+amp*(+1.97294*Math.cos(angle));
+
+    r=Math.max(Math.min(r,1.0),0.0);
+    g=Math.max(Math.min(g,1.0),0.0);
+    b=Math.max(Math.min(b,1.0),0.0);
+
+    if(irgb == 1){
+      return r;
+    }
+    else if(irgb == 2) {
+      return g;
+    }
+    else {
+      return b;
+    }
+}
+
+// ----------------------------------------------------------------------------
+
+function CubeHelixFract(i,n,flip){
+    var fraction = i/(n-1);
+    if (flip == 1) {
+      fraction = 1 - fraction;
+    }
+    return fraction;
+}