canvas

    var canvas = document.createElement("canvas");//創建canvas對象
    var context = canvas.getContext("2d");//返回Context對象
    context.rect(0 , 0 , canvas.width , canvas.height);//創建矩形
    context.fillStyle = "#fff";//設置填充顏色
    context.fill();//填充圖像
    context.drawImage(myImage , 0 , 0);//畫圖
    myImage2.src = child_img.attr('src');   //你自己本地的圖片或者在線圖片
    context.drawImage(myImage2 , x , y );//畫圖
    var img_base64 = canvas.toDataURL("image/png");  //"image/png" , 轉換爲base64格式