Draw Gauge Chart By Canvas

I can draw gauge chart by canvas with function arc(). But, the shape is a half of circle. Now, I'd like to draw gaugle chart like this (please ignore color or number). How can I

Solution 1:

Just stroke an arc with a sweep-angle based on your desired gauge percentage.

In your example the 0% angle is (estimating...)

PI * 0.60 

and your 100% angle is (again estimating...)

PI*2 + PI*.40

So your arc will always start at angle = PI*0.60.

Your arc will end at the angle calculated like this:

zeroAngle + (hundredAngle-zeroAngle) * guagePercentageValue

Here's example code and a Demo:

var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var cw=canvas.width;
var ch=canvas.height;

var PI=Math.PI;
var PI2=PI*2;
var cx=150;
var cy=150;
var r=80;
var min=PI*.60;
var max=PI2+PI*.40;
var percent=50;

ctx.lineCap='round';
ctx.font='24px verdana';
ctx.textAlign='center';
ctx.textBaseline='middle';
ctx.fillStyle='gray';

$myslider=$('#myslider');
$myslider.attr({min:0,max:100}).val(50);
$myslider.on('input change',function(){
  percent=parseInt($(this).val());
  drawGuage();
});

drawGuage();

function drawGuage(){
  ctx.clearRect(0,0,cw,ch);
  // draw full guage outline
  ctx.beginPath();
  ctx.arc(cx,cy,r,min,max);
  ctx.strokeStyle='lightgray';
  ctx.lineWidth=15;
  ctx.stroke();
  // draw percent indicator
  ctx.beginPath();
  ctx.arc(cx,cy,r,min,min+(max-min)*percent/100);
  ctx.strokeStyle='red';
  ctx.lineWidth=6;
  ctx.stroke();
  ctx.fillText(percent+'%',cx,cy);
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<input id=myslider type=range><br>
<canvas id="canvas" width=300 height=300></canvas>