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实现鼠标拖动canvas绘制的图片

不啰嗦上代码:

<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><title>无标题文档</title></head><body><canvas id="gameCanvas" width="500px" height="300px"></canvas><script>var cvs = document.getElementById(‘gameCanvas‘);var ctx = cvs.getContext(‘2d‘);//绘制黑色背景ctx.fillStyle = ‘black‘;ctx.fillRect(0, 0, 500,300);//绘制红色矩形ctx.fillStyle = ‘red‘;ctx.fillRect(100, 100, 100,100);//记录矩形的位置var posX = 100;var posY = 100;        cvs.onmousedown = function(e){    var x = e.clientX - posX;    var y = e.clientY - posY;    //判断鼠标是否点击在矩形内    if(e.clientX >= posX + this.offsetLeft && e.clientX <= posX + 100 + this.offsetLeft && e.clientY >= posY + this.offsetTop && e.clientY <= posY + 100 + this.offsetTop){            document.onmousemove = function(e){            //ctx.clearRect(posX, posY, 100,100);                        //鼠标拖动时重绘黑色背景            ctx.fillStyle = ‘black‘;            ctx.fillRect(0, 0, 500,300);            //鼠标拖动时重绘红色矩形            ctx.fillStyle = ‘red‘;                ctx.fillRect(e.clientX-x, e.clientY-y, 100,100);            //记录矩形的位置            posX = e.clientX-x;            posY = e.clientY-y;        };        document.onmouseup = function(){            document.onmousemove = null;        };    }};</script></body></html>

 

实现鼠标拖动canvas绘制的图片