html5 canvas自定义画板

￡神魔★判官ぃ 2022-08-02 12:44 221阅读 0赞

<!DOCTYPE HTML>
    <html>
    <head>
    <meta charset="utf-8" />
    </head>
    <body>
    
    
    
    定义画板<br />
    <canvas id="myCanvas" width="1200" height="600">
    你的浏览器不支持HTML5
    </canvas>
    <br/><br/>画笔颜色:
    <button style="width:80px;background-color:yellow;" onclick='linecolor="yellow";'>Yellow</button>
    <button style="width:80px;background-color:#00FF00;" onclick='linecolor="#00FF00";'>Lime</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:#E238EC;" onclick='linecolor="#E238EC";'>Crimson</button>
    <button style="width:100px;background-color:#FDD017;" onclick='linecolor="#FDD017";'>Bright Gold</button>
    <button style="width:80px;background-color:navy;" onclick='linecolor="navy";'>Navy</button>
    <button style="width:80px;background-color:lightblue;" onclick='linecolor="lightblue";'>LightBlue</button>
    <button style="width:80px;background-color:gray;" onclick='linecolor="gray";'>Gray</button>
    <br />画笔粗细:
    <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>
    <br />导出画板:
    <button style="width:1s80px;background-color:pink;" onclick="copyimage();">Export Canvas To Image</button>
    <br /><br />
    <img src="" id="image_png" width="600" height="300">
    <script type="text/javascript">
    	var canvas = document.getElementById("myCanvas");
    	var ctx = canvas.getContext("2d");
    
    	//画一个黑色矩形
    	ctx.fillStyle = "black";
    	ctx.fillRect(0, 0, 1200, 600);
    	
    	//按下标记
    	var onoff = false;
    	var oldx = -10;
    	var oldy = -10;
    	
    	//设置画笔颜色
    	var linecolor = "white";
    	//设置线宽
    	var linw = 4;
    	//添加鼠标移动事件
    	canvas.addEventListener("mousemove", draw, true);
    	//添加鼠标按下事件
    	canvas.addEventListener("mousedown", down, false);
    	//添加鼠标弹起事件
    	canvas.addEventListener("mouseup", up, false);
    	
    	/**
    	* 鼠标按下事件
    	**/
    	function down(event){
    		onoff = true;
    		//记录鼠标按下时的坐标做画线的起始坐标
    		oldx = event.pageX-10;
    		oldy = event.pageY-10;
    	}
    	/**
    	* 鼠标弹起事件
    	**/
    	function up(event){
    		onoff = false;
    		var oldx = -10;
    	    var oldy = -10;
    	}
    	/**
    	* 鼠标移动事件
    	**/
    	function draw(event){
    		if(true == onoff){
    			//移动时的新坐标做画线的终止坐标
    			var newx = event.pageX-10;
    			var newy = event.pageY-10;
    			//开始画线
    			ctx.beginPath();
    			//设置画线起点
    			ctx.moveTo(oldx, oldy);
    			//设置画线终点
    			ctx.lineTo(newx, newy);
    			//设置画笔颜色
    			ctx.strokeStyle = linecolor;
    			//设置画笔粗细
    			ctx.lineWidth = linw;
    			//设置笔帽
    			ctx.lineCap = "round";
    			//完成画线
    			ctx.stroke();
    			
    			//设置本次坐标为下次画线的起始坐标
    			oldx = newx;
    			oldy = newy;
    		}
    	}
    	
    	//导出画板
    	function copyimage(event){
    		var img_png_src = canvas.toDataURL("image/png");
    		document.getElementById("image_png").src = img_png_src;
    	}
    </script> 
    
    </body>
    </html>