JavaScript html5 canvas实现图片上画超链接

<canvas id="canvasFile" style="margin-top:15px;" width="500" height="400"></canvas> 
<input type="button" id="btnRedo" value="Re-Draw" class="btn btn-warning"/> 

var photoW = 400; 
 var photoH = 300; 
 var photo; 
 
 
 // logic load image into canvas 
 // ... 
 // e.g. 
 // photo = new Image(); 
 // photo.onload = function() { 
 // draw photo into canvas when ready 
 // ctx.drawImage(photo, 0, 0, photoW, photoH); 
 // }; 
 // load photo into canvas 
 // photo.src = picURL; 
 
 
 // canvas highlight 
 var canvas = document.getElementById('canvasFile'), 
 ctx = canvas.getContext('2d'), 
 img = new Image; 
 var btnDone = document.getElementById('btnDone'); 
 var btnRedo = document.getElementById('btnRedo'); 
 
 
 ctx.strokeStyle = '#FF0000'; 
 
 function DrawDot(x, y) { 
 var centerX = x; 
 var centerY = y; 
 var radius = 2; 
 
 
 ctx.beginPath(); 
 ctx.arc(centerX, centerY, radius, 0, 2 * Math.PI, false); 
 ctx.fillStyle = 'red'; 
 ctx.fill(); 
 ctx.lineWidth = 2; 
 ctx.strokeStyle = '#FF0000'; 
 ctx.stroke(); 
 } 
 
 
 function startDrawing() { 
 ctx.drawImage(img, 0, 0, photoW, photoH); 
 canvas.onmousemove = mousemoving; 
 canvas.onmousedown = mousedownhandle; 
 canvas.onmouseup = mouseuphandle; 
 // ## mobile events 
 //touchstart – to toggle drawing mode “on” 
 //touchend – to toggle drawing mode “off” 
 //touchmove – to track finger position, used in drawing 
 canvas.addEventListener('touchmove', touchmove, false); 
 canvas.addEventListener('touchend', mouseuphandle, false); 
 
 
 btnRedo.onclick = function (e) { 
 ctx.clearRect(0, 0, ctx.width, ctx.height); 
 ctx.drawImage(photo, 0, 0, photoW, photoH); 
 savedrawing(); 
 } 
 } 
 function savedrawing(e) { 
 var image = document.getElementById('canvasFile').toDataURL("image/jpeg"); 
 image = image.replace('data:image/jpeg;base64,', ''); 
 $("#imgNric1").val(image); 
 }; 
 

 function mousemoving(e) { 
 if (drawing) { 
 mousedownhandle(e); 
 } 
 } 
 
 
 var drawing = false; 
 
 
 function mousedownhandle(e) { 
 drawing = true; 
 var r = canvas.getBoundingClientRect(), 
 x = e.clientX - r.left, 
 y = e.clientY - r.top; 
 
 
 DrawDot(x, y); 
 } 
 
 function mouseuphandle(e) { 
 savedrawing(); 
 e.preventDefault(); 
 drawing = false; 
 
 } 
 
 
 //// mobile touch events 
 function touchmove(e) { 
 if (e.clientX > 800) { 
 mousedownhandle(e); 
 return; 
 } 
 
 var r = canvas.getBoundingClientRect(), 
 //event.changedTouches[0].pageX + ":" + event.changedTouches[0].pageY; 
 x = e.changedTouches[0].pageX - r.left, 
 y = e.changedTouches[0].pageY - r.top; 
 
 
 DrawDot(x, y); 
 e.preventDefault(); 
 }