Perform gamma transform (with fixed z0 of unity)

Author: waxlamp

src/traces/scattersmith/calc.js

@@ -10,6 +10,32 @@ var arraysToCalcdata = require('../scatter/arrays_to_calcdata');
 var calcSelection = require('../scatter/calc_selection');
 var calcMarkerSize = require('../scatter/calc').calcMarkerSize;
 
+function sq(x) {
+  return x * x;
+}
+
+function gammaTransformReal(re, im) {
+  var denom = sq(re + 1.0) + sq(im);
+  var result = (sq(re) + sq(im) - 1.0) / denom;
+  return result;
+}
+
+function gammaTransformImaginary(re, im) {
+  var denom = sq(re + 1.0) + sq(im);
+  var result = (2 * im) / denom;
+  return result;
+}
+
+function cart2pol(re, im) {
+  var r = Math.sqrt(sq(re) + sq(im));
+  var theta = Math.atan2(im, re);
+
+  return {
+    r: r,
+    theta: theta,
+  };
+}
+
 module.exports = function calc(gd, trace) {
     var fullLayout = gd._fullLayout;
     var subplotId = trace.subplot;
@@ -26,8 +52,10 @@ module.exports = function calc(gd, trace) {
         var cdi = cd[i] = {};
 
         if(isNumeric(re) && isNumeric(im)) {
-            cdi.re = re;
-            cdi.im = im;
+            var pol = cart2pol(gammaTransformReal(re, im), gammaTransformImaginary(re, im));
+
+            cdi.re = pol.r;
+            cdi.im = pol.theta;
         } else {
             cdi.re = BADNUM;
         }