grad_circle.js

Bangle.setLCDMode();
g.clear();
function hex(c) {
  var s = "0123456789abcdef";
  var i = parseInt (c);
  if (i == 0 || isNaN (c))
    return "00";
  i = Math.round (Math.min (Math.max (0, i), 255));
  return s.charAt ((i - i % 16) / 16) + s.charAt (i % 16);
}
function convertToHex (rgb) {
  return hex(rgb[0]) + hex(rgb[1]) + hex(rgb[2]);
}
function trim (s) { return (s.charAt(0) == '#') ? s.substring(1, 7) : s;}
function convertToRGB (hex) {
  var color = [];
  color[0] = parseInt ((trim(hex)).substring (0, 2), 16);
  color[1] = parseInt ((trim(hex)).substring (2, 4), 16);
  color[2] = parseInt ((trim(hex)).substring (4, 6), 16);
  return color;
}
function generateColor(colorStart,colorEnd,colorCount){
    var start = convertToRGB (colorStart);
    var end   = convertToRGB (colorEnd);
    var len = colorCount;
    var alpha = 0.0;
    var saida = [];
    for (i = 0; i < len; i++) {
		var c = [];
		alpha += (1.0/len);
		c[0] = Math.round(start[0] * alpha + (1 - alpha) * end[0]);
		c[1] = Math.round(start[1] * alpha + (1 - alpha) * end[1]);
		c[2] = Math.round(start[2] * alpha + (1 - alpha) * end[2]);
		saida.push(c);
	}
  return saida;
}
const Width  = g.getWidth(),  CenterX = Math.floor(Width)/2;
const Height = g.getHeight(), CenterY = Math.floor(Height)/2;
let Radius = Math.min(CenterX,CenterY), RadiusSquared = Radius*Radius;

var tmp = generateColor('#ff0ff0','#ff0f67',Radius);
print(convertToHex(tmp[0]));

for(let i=0;i< tmp.length; i++){
  g.setColor('#'+convertToHex(tmp[i]));
  g.fillCircle(CenterX,CenterY,Radius);
  Radius = Radius -1;
}