Drawing circle/ellipse on HTML5 canvas using mouse events - Javascript Canvas

Javascript examples for Canvas:Mouse

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Description

Drawing circle/ellipse on HTML5 canvas using mouse events

Demo Code

ResultView the demo in separate window 

<!doctype html>
<html>
   <head> 
      <!-- reset css --> 
      <script type="text/javascript" src="https://code.jquery.com/jquery.min.js"></script> 
      <style>

#canvas{ border:1px solid blue; }

      </style> 
      <script>
$(function(){/*from   ww w  .j  a  v  a2s.c o m*/
    var canvas=document.getElementById("canvas");
    var ctx=canvas.getContext("2d");
    var canvasOffset=$("#canvas").offset();
    var offsetX=canvasOffset.left;
    var offsetY=canvasOffset.top;
    var startX;
    var startY;
    var isDown=false;
    function drawOval(x,y){
        ctx.clearRect(0,0,canvas.width,canvas.height);
        ctx.beginPath();
        ctx.moveTo(startX, startY + (y-startY)/2);
        ctx.bezierCurveTo(startX, startY, x, startY, x, startY + (y-startY)/2);
        ctx.bezierCurveTo(x, y, startX, y, startX, startY + (y-startY)/2);
        ctx.closePath();
        ctx.stroke();
    }
    function handleMouseDown(e){
      e.preventDefault();
      e.stopPropagation();
      startX=parseInt(e.clientX-offsetX);
      startY=parseInt(e.clientY-offsetY);
      isDown=true;
    }
    function handleMouseUp(e){
      if(!isDown){ return; }
      e.preventDefault();
      e.stopPropagation();
      isDown=false;
    }
    function handleMouseOut(e){
      if(!isDown){ return; }
      e.preventDefault();
      e.stopPropagation();
      isDown=false;
    }
    function handleMouseMove(e){
      if(!isDown){ return; }
      e.preventDefault();
      e.stopPropagation();
      mouseX=parseInt(e.clientX-offsetX);
      mouseY=parseInt(e.clientY-offsetY);
      drawOval(mouseX,mouseY);
    }
    $("#canvas").mousedown(function(e){handleMouseDown(e);});
    $("#canvas").mousemove(function(e){handleMouseMove(e);});
    $("#canvas").mouseup(function(e){handleMouseUp(e);});
    $("#canvas").mouseout(function(e){handleMouseOut(e);});
}); // end $(function(){});

      </script> 
   </head> 
   <body> 
      <h4>Drag to create a circle or oval</h4> 
      <canvas id="canvas" width="300" height="300"></canvas>  
   </body>
</html>

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