HTML5 Canvas drawing ellipse with mouse - Javascript Canvas

Javascript examples for Canvas:Mouse

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Description

HTML5 Canvas drawing ellipse with mouse

Demo Code

ResultView the demo in separate window 

<html>
   <head> 
      <title>Draw ellipse on canvas with mouse</title> 
      <meta name="viewport" content="width=device-width, initial-scale=1"> 
      <script type="text/javascript" src="https://code.jquery.com/jquery-2.1.3.js"></script> 
      <style id="compiled-css" type="text/css">

canvas {//from w  w w.  j  a  va  2  s . c  o m
   cursor: crosshair;
   border: 1px solid #000000;
}


      </style> 
      <script type="text/javascript">
    $(window).load(function(){
//Canvas
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');

var canvasx = $(canvas).offset().left;
var canvasy = $(canvas).offset().top;
var last_mousex = last_mousey = 0;
var mousex = mousey = 0;
var mousedown = false;
//Mousedown
$(canvas).on('mousedown', function(e) {
    last_mousex = parseInt(e.clientX-canvasx);
   last_mousey = parseInt(e.clientY-canvasy);
    mousedown = true;
});
//Mouseup
$(canvas).on('mouseup', function(e) {
    mousedown = false;
});
//Mousemove
$(canvas).on('mousemove', function(e) {
    mousex = parseInt(e.clientX-canvasx);
   mousey = parseInt(e.clientY-canvasy);
    if(mousedown) {
        ctx.clearRect(0,0,canvas.width,canvas.height); //clear canvas
        //Save
        ctx.save();
        ctx.beginPath();

        var scalex = 1*((mousex-last_mousex)/2);
        var scaley = 1*((mousey-last_mousey)/2);
        ctx.scale(scalex,scaley);

        var centerx = (last_mousex/scalex)+1;
        var centery = (last_mousey/scaley)+1;
        ctx.arc(centerx, centery, 1, 0, 2*Math.PI);

        ctx.restore();
        ctx.strokeStyle = 'black';
        ctx.lineWidth = 5;
        ctx.stroke();
    }
    //Output
    $('#output').html('current: '+mousex+', '+mousey+'<br/>last: '+last_mousex+', '+last_mousey+'<br/>mousedown: '+mousedown);
});
    });

      </script> 
   </head> 
   <body> 
      <canvas id="canvas" width="800" height="500"></canvas> 
      <div id="output"></div>  
   </body>
</html>

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