HTML5画布在非矩形部分中裁剪并保存图像

Question

I have been trying for the past few days to crop a image in a manner the user wants it.....i needed to provide the user with a UI where he can cut a part of a image by drawing circles or by joining points...So i found out a fiddle where user can draw points and when he clicks generate button the image gets created with part he wants to crop...... but when i am trying to get the dataUrl property of the newly generated canvas which has the cropped image it gives me error which says "Security Error: The operation is insecure."

I want the dataUrl property of the newly generated canvas so that i can get the base64 value and save the newly cropped image to a folder...is there any way i can overcome this error....i have goggled the error but dint got any solution....the one thing i came to know is its some flag is set to off canvas which is why m unable to get the datUrl property

Here is the fiddle [ http://jsfiddle.net/MFELx/] which has demo where we can crop an image by clicking dots on image....can u please update this fiddle to get me the dataUrl property of the newly generated canvas or any other method will also be appreciated

Following is the html

<div id="mainContent">
<div id="canvasDiv">
<br/>
<button id="generate" type="button">Generate
</button> 
</div>
<h1>Result:</h1>
<div class="clipParent" style="float:left;"> 
</div> 
</div>

Following is the script

var canvasDiv = document.getElementById('canvasDiv'); 
canvas = document.createElement('canvas'); 
canvas.setAttribute('width', 500); 
canvas.setAttribute('height', 500); 
canvas.setAttribute('id', 'canvas'); 
$(canvasDiv).prepend(canvas); 
if(typeof G_vmlCanvasManager != 'undefined') { 
    canvas = G_vmlCanvasManager.initElement(canvas); 
} 

var context = canvas.getContext('2d'); 
var imageObj = new Image(); 

imageObj.onload = function() {
    $(canvas).attr({width : this.width, height: this.height});
    context.drawImage(imageObj,0,0); 
}; 
imageObj.src = 'http://www.html5canvastutorials.com/demos/assets/darth-vader.jpg'; 

var clickX = new Array(); 
var clickY = new Array(); 
var clickDrag = new Array(); 
var paint; 

function addClick(x, y, dragging) 
{ 
    clickX.push(x); 
    clickY.push(y); 
    clickDrag.push(dragging); 
} 

function redraw(){ 
    canvas.width = canvas.width; // Clears the canvas 
    context.drawImage(imageObj,0,0); 

    context.strokeStyle = "#df4b26"; 
    context.lineJoin = "round"; 
    context.lineWidth = 5; 

    for(var i=0; i < clickX.length; i++) 
    { 
    context.beginPath(); 
    context.arc(clickX[i], clickY[i], 3, 0, 2 * Math.PI, false); 
    context.fillStyle = '#ffffff'; 
    context.fill(); 
    context.lineWidth = 5; 
    context.stroke(); 
    } 
} 

$('#canvas').click(function(e){ 
    var mouseX = e.pageX - this.offsetLeft; 
    var mouseY = e.pageY - this.offsetTop; 

    addClick(e.pageX - this.offsetLeft, e.pageY - this.offsetTop); 
    redraw(); 
}); 

$('#generate').click(function(){ 
    $(".clipParent").empty(); 
    $(".clipParent").prepend('<img src="http://www.html5canvastutorials.com/demos/assets/darth-vader.jpg" id="genimg" />'); 
    var arr = []; 
    for(var i=0; i < clickX.length; i++){ 
        arr.push(clickX[i]); 
        arr.push(clickY[i]); 
    } 
    $("#genimg")[0].setAttribute("data-polyclip",arr.join(", ")); 
    clickX=[]; 
    clickY=[]; 
    redraw(); 
    polyClip.init(); 
});

Thanks in advanced guys

Answer 1

"Security Error: The operation is insecure."

You can't use images for canvas from other domains, only from origin domain. Read about this here http://www.w3.org/TR/cors/#resource-sharing-check-0 (CORS).