JS canvas 画板撤销

<!DOCTYPE html>

<html>

<head>

    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />

    <title></title>

    <style type="text/css">

        #button{

            width: 60px;

            height: 20px;

        }

    </style>

</head>

<body>

    <canvas id="canvas" width="600px" height="400px" style="background: #DBDDDF; "></canvas>

    <input type="button" value="撤销" id="button">

    <script type="text/javascript">

        var canvas=document.getElementById('canvas');

        var cext=canvas.getContext('2d');

        cext.strokeStyle="black";

        cext.lineWidth=2;

        cext.fillStyle="black";

        function getStyles(obj){//兼容FF，IE10; IE9及以下未测试

            return document.defaultView.getComputedStyle(obj);

        }

        function getCanvasPos(canvas,e)

        {//获取鼠标在canvas上的坐标

            var rect = canvas.getBoundingClientRect();

            var leftB = parseInt(getStyles(canvas).borderLeftWidth);//获取的是样式，需要转换为数值

            var topB = parseInt(getStyles(canvas).borderTopWidth);

            return {

                x: (e.clientX - rect.left) - leftB,

                y: (e.clientY - rect.top) - topB

           };

        } 

        var restorePoint = {};

        var shuzu=[];

        var h=0;

        var x1,x2,newx,newy;

        canvas.onmousedown=function (e) {

            restorePoint = cext.getImageData(0, 0, canvas.width, canvas.height);

            x1=getCanvasPos(canvas,e).x;

            x2=getCanvasPos(canvas,e).y;

            canvas.onmousemove=function(e){

                cext.putImageData(restorePoint, 0, 0);

                newx=getCanvasPos(canvas,e).x;

                newy=getCanvasPos(canvas,e).y;

                cext.beginPath();

                cext.moveTo(x1,x2);

                cext.lineTo(newx,newy);

                cext.stroke();

                cext.closePath();

            }

        }

        canvas.onmouseup=function(){

            shuzu[h] = restorePoint;

            h++;

            canvas.onmousemove=null;

        }

        document.getElementById("button").onmousedown=function(){

            restorePoint = shuzu[h-1];

                    cext.putImageData(restorePoint, 0, 0);

                    h--;

        }

    </script>

</body>

</html>
巴特西

JS canvas 画板撤销

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巴特西

JS canvas 画板 撤销

最新文章

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JS canvas 画板撤销
