download:小马哥的 Java 我的项目实战营【完结】
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<head>
<meta charset="utf-8"><title>DEMO6：自定义画板</title></head>
<body>
<canvas id="canvas" width="600" height="300">
浏览器不反对canvas <!-- 如果不反对会显示这段文字 --></canvas>
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<button style="width:80px;background-color:yellow;" onclick='linecolor="yellow";'>YELLOW</button>
<button style="width:80px ;background-color:red;" onclick='linecolor="red";'>RED</button>
<button style="width:80px ;background-color:blue;" onclick='linecolor="blue";'>BLUE</button>
<button style="width:80px ;background-color:green;" onclick='linecolor="green";'>GREEN</button>
<button style="width:80px ;background-color:white;" onclick='linecolor="white";'>WHITE</button>
<button style="width:80px ;background-color:black;" onclick='linecolor="black";'>BLACK</button>
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<button style="width: 80px;background-color: white;" onclick="linw=4;">4PX</button>
<button style="width: 80px;background-color: white;" onclick="linw=8;">8PX</button>
<button style="width: 80px;background-color: white;" onclick="linw=16;">16PX</button>
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<button style="width: 80px;background-color: white;" onclick="copyimage();">EXPORT</button>
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<img src="" id="image_png" width="600px" height="300px">
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<script type="text/javascript">
var canvas = document.getElementById('canvas'); //获取标签var ctx = canvas.getContext("2d"); var fillStyle = "black";ctx.fillRect(0,0,600,300);var onoff = false; //按下标记var oldx = -10;var oldy = -10;//设置色彩var linecolor = "white";var linw = 4;canvas.addEventListener("mousemove",draw,true); //鼠标挪动事件canvas.addEventListener("mousedown",down,false); //鼠标按下事件canvas.addEventListener("mouseup",up,false); //鼠标弹起事件function down(event){ onoff = true; oldx = event.pageX - 10; oldy = event.pageY - 10;}function up(){ onoff = false;}function draw(event){ if (onoff==true) { var newx = event.pageX - 10; var newy = event.pageY - 10 ctx.beginPath(); ctx.moveTo(oldx,oldy); ctx.lineTo(newx,newy); ctx.strokeStyle = linecolor; ctx.lineWidth = linw; ctx.lineCap = "round"; ctx.stroke(); oldx = newx; oldy = newy; }}function copyimage(event){ var img_png_src = canvas.toDataURL("image/png"); //将画板保留为图片格式的函数 document.getElementById("image_png").src = img_png_src;} </script> </body>
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