利用canvas裁剪想要的图片

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="../jquery-1.9.1.min.js"></script>
    <meta name="viewport" content="width=device-width,initial-scale=1.0,maximum-scale=1.0,user-scalable=0" />
    <style>
        #container {
            display: inline-block;
            position: relative;
        }

        .mask {
            background: black;
            opacity: 0.3;
            border: 1px solid green;
            width: 150px;
            height: 150px;
            left: 0;
            top: 0;
            z-index: 22;
            position: absolute;
        }
    </style>

</head>
<body>

<input type="file" id="imgInp">
<br>
<span id="container">
    <div class="mask"></div>
    <img id="tulip">
</span>
<br>
<canvas id="myCanvas" width="150px" height="150px"></canvas>
<br>
<button id="caijian" onclick="cai()">裁剪</button>
<script src="vconsole.min.js"></script>
<script>
    var con=new VConsole();
    var c = ""
    var ctx =""
    window.iiix = 0;
    window.iiiy = 0;
    function cai() {

        caijian(window.iiix, window.iiiy)
        //console.log(c.toDataURL("image/png"))
    }

    function ImgZoom(Id)
    {
        var w = Id.width;
        var m = 350;
        if(w < m)
        {
            return;
        }
        else
        {
            var h = Id.height;
            Id.height = parseInt(h*m/w);
            Id.width = m;
        }
    }

    function caijian(sx, sy) {
        c = document.getElementById("myCanvas");
         ctx = c.getContext("2d");
        var img = document.getElementById("tulip");
        ctx.drawImage(img, sx, sy, 150, 150, 0, 0,150,150);
    }
    function readURL(input) {
        if (input.files && input.files[0]) {
            var reader = new FileReader();
            reader.onload = function (e) {
                $('#tulip').attr('src', e.target.result);
                var img=new Image()
                img.src=e.target.result

                console.log(img.naturalWidth)
            }
            reader.readAsDataURL(input.files[0]);
        }
    }
    $("#imgInp").change(function () {
        readURL(this);
    });
  /*  $(".mask").mousedown(function () {
        onMouseU55p()
        onMouseDow555n()
    });*/
    var mask=document.getElementsByClassName("mask")[0];
    function onMouseDow555n() {
        mask.addEventListener("touchmove",onMouseMove,false);
        onMouseU55p();
    }
    function onMouseU55p() {
        mask.addEventListener("touchend",function(){
            mask.removeEventListener("touchmove",onMouseMove);
        },false);
    }



    mask.addEventListener("touchstart",function(e){
        onMouseDow555n()
    },false);


 /*   $(".mask").mousedown(function () {
        onMouseUp()
        onMouseDown()
    });
    function onMouseDown() {
        $(".mask").bind("mousemove", onMouseMove)
    }
    function onMouseUp() {
        $(".mask").bind("mouseup", function () {
            $(".mask").unbind("mousemove", onMouseMove)
        })
    }*/


    function onMouseMove(event) {
        var top = $(this).position().top
        var left = $(this).position().left
        //console.log(top,left);
        //边界
        //left
        var leftlimit = $(this).parent().width() - $(this).width();
        var toplimit = $(this).parent().height() - $(this).height();
        //console.log(leftlimit,toplimit);
//这里可以得到鼠标Y坐标
       /* var pointX = e.pageX;screenX
        var pointY = e.pageY;*/

         var pointX =  event.targetTouches[0].pageX;
         var pointY =  event.targetTouches[0].pageY;
        console.log(pointX, pointY);

        //父元素的坐标
        var parentX = $(this).parent().offset().left;
        var parentY = $(this).parent().offset().top;

        console.log("父", parentX, parentY);
        var realX = pointX - parentX;
        var realY = pointY - parentY;
        window.iiix = realX - $(this).width() / 2
        window.iiiy = realY - $(this).height() / 2
        console.log("实", window.iiix, window.iiiy);
        var itemX = realX - $(this).width() / 2
        var itemY = realY - $(this).height() / 2
        if (realX >= leftlimit + $(this).width() / 2) {
            itemX = leftlimit
        }
        if (realY >= toplimit + $(this).height() / 2) {
            itemY = toplimit
        }
        if (realX <= $(this).width() / 2) {
            itemX = 0
        }
        if (realY <= $(this).height() / 2) {
            itemY = 0
        }

        $(this).css("top", itemY)
        $(this).css("left", itemX)

        //鼠标的位置

    }


</script>
</body>
</html>
利用canvas裁剪想要的图片

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