radial gradient color effect on concentric circles - geometry

Question

How to apply gradient colors on 5 concentric circles using html5 canvas
gradient = context.createRadialGradient(startx, starty,radAvg, xEnd, yEnd,radAvg);
gradient.addColorStop(0, startColor);
gradient.addColorStop(1.0, endColor);
Current results:
JavaScript code:
var colors = ["#B8D430", "#3AB745", "#029990", "#3501CB",
"#2E2C75", "#673A7E", "#CC0071", "#F80120",
"#F35B20", "#FB9A00", "#FFCC00", "#FEF200"];
var restaraunts = ["Wendy's", "McDonalds", "Chick-fil-a", "Five Guys",
"Gold Star", "La Mexicana", "Chipotle", "Tazza Mia",
"Panera", "Just Crepes", "Arby's", "Indian"];
var startAngle = 0;
var arc = Math.PI / 6;
var spinTimeout = null;
var spinArcStart = 10;
var spinTime = 0;
var spinTimeTotal = 0;
var ctx;
function draw() {
drawRouletteWheel();
}
function drawRouletteWheel() {
var canvas = document.getElementById("wheelcanvas");
if (canvas.getContext) {
var outsideRadius = 200;
var textRadius = 160;
var insideRadius = 125;
ctx = canvas.getContext("2d");
ctx.clearRect(0,0,500,500);
ctx.strokeStyle = "black";
ctx.lineWidth = 2;
ctx.font = 'bold 12px sans-serif';
for(var i = 0; i < 12; i++) {
var angle = startAngle + i * arc;
ctx.fillStyle = colors[i];
ctx.beginPath();
ctx.arc(250, 250, outsideRadius, angle, angle + arc, false);
ctx.arc(250, 250, insideRadius, angle + arc, angle, true);
ctx.stroke();
ctx.fill();
ctx.save();
ctx.shadowOffsetX = -1;
ctx.shadowOffsetY = -1;
ctx.shadowBlur = 0;
ctx.shadowColor = "rgb(220,220,220)";
// ctx.fillStyle = "black";
ctx.translate(250 + Math.cos(angle + arc / 2) * textRadius, 250 + Math.sin(angle + arc / 2) * textRadius);
ctx.rotate(angle + arc / 2 + Math.PI / 2);
var text = restaraunts[i];
ctx.fillText(text, -ctx.measureText(text).width / 2, 0);
ctx.restore();
}
//Arrow
ctx.fillStyle = "black";
ctx.beginPath();
ctx.moveTo(250 - 4, 250 - (outsideRadius + 5));
ctx.lineTo(250 + 4, 250 - (outsideRadius + 5));
ctx.lineTo(250 + 4, 250 - (outsideRadius - 5));
ctx.lineTo(250 + 9, 250 - (outsideRadius - 5));
ctx.lineTo(250 + 0, 250 - (outsideRadius - 13));
ctx.lineTo(250 - 9, 250 - (outsideRadius - 5));
ctx.lineTo(250 - 4, 250 - (outsideRadius - 5));
ctx.lineTo(250 - 4, 250 - (outsideRadius + 5));
ctx.fill();
}
}
function spin() {
spinAngleStart = Math.random() * 10 + 10;
spinTime = 0;
spinTimeTotal = Math.random() * 3 + 4 * 1000;
rotateWheel();
}
function rotateWheel() {
spinTime += 30;
if(spinTime >= spinTimeTotal) {
stopRotateWheel();
return;
}
var spinAngle = spinAngleStart - easeOut(spinTime, 0, spinAngleStart, spinTimeTotal);
startAngle += (spinAngle * Math.PI / 180);
drawRouletteWheel();
spinTimeout = setTimeout('rotateWheel()', 30);
}
function stopRotateWheel() {
clearTimeout(spinTimeout);
var degrees = startAngle * 180 / Math.PI + 90;
var arcd = arc * 180 / Math.PI;
var index = Math.floor((360 - degrees % 360) / arcd);
ctx.save();
ctx.font = 'bold 30px sans-serif';
var text = restaraunts[index]
ctx.fillText(text, 250 - ctx.measureText(text).width / 2, 250 + 10);
ctx.restore();
}
function easeOut(t, b, c, d) {
var ts = (t/=d)*t;
var tc = ts*t;
return b+c*(tc + -3*ts + 3*t);
}
draw();

Answer 1

here is my solution
var Mid_diff=(startAngle+endAngle)/2;
var dest_x=arc.center.x+(arc.maxRadius*Math.cos(Mid_diff));
var dest_y=arc.center.y+(arc.maxRadius*Math.sin(Mid_diff));
var gradient = context.createRadialGradient( arc.center.x,arc.center.y,0,dest_x,dest_y,arc.maxRadius);
gradient.addColoStop(0,rgba(0,12,107,0);
gradient.addColoStop(1,rgba(0,12,107,1);
context.strokeStyle = gradient;
worked