HTML5canvas绘图基本详解

本文主要和大家介绍HTML5 canvas绘图基本使用方法的相关资料，小编觉得挺不错的，现在分享给大家，也给大家做个参考。一起跟随小编过来看看吧，希望能帮助到大家。

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>canvas绘图演示</title>
    <style type="text/css">
        #canvas{
            border: 1px solid #ADACB0;
            display: block;
            margin: 20px auto;
        }
    </style>
</head>
<body>
    <canvas id="canvas" width="300" height="300">
        你的浏览器还不支持canvas
    </canvas>
</body>
<script type="text/javascript">
    var canvas = document.getElementById("canvas");
    var context = canvas.getContext("2d");
    //设置对象起始点和终点
    context.moveTo(10,10);
    context.lineTo(200,200);
    //设置样式
    context.lineWidth = 2;
    context.strokeStyle = "#F5270B";
    //绘制
    context.stroke();
</script>
</html>

 <script type="text/javascript">
    var canvas = document.getElementById("canvas");
    var context = canvas.getContext("2d");
    //设置对象起始点和终点
    context.beginPath();
    context.moveTo(100,100);
    context.lineTo(700,100);
    context.lineTo(700,400);
    context.lineWidth = 2;
    context.strokeStyle = "#F5270B";
    //绘制
    context.stroke();

    context.beginPath();
    context.moveTo(100,200);//这里的moveTo换成lineTo效果是一样的
    context.lineTo(600,200);
    context.lineTo(600,400);
    //strokeStyle的颜色有新的值，则覆盖上面设置的值
    //lineWidth没有新的值，则按上面设置的值显示
    context.strokeStyle = "#0D25F6";
    //绘制
    context.stroke();
</script>

 <script type="text/javascript">
    var canvas = document.getElementById("canvas");
    var context = canvas.getContext("2d");

    //使用rect方法
    context.rect(10,10,190,190);
    context.lineWidth = 2;
    context.fillStyle = "#3EE4CB";
    context.strokeStyle = "#F5270B";
    context.fill();
    context.stroke();

    //使用fillRect方法
    context.fillStyle = "#1424DE";
    context.fillRect(210,10,190,190);

    //使用strokeRect方法
    context.strokeStyle = "#F5270B";
    context.strokeRect(410,10,190,190);

    //同时使用strokeRect方法和fillRect方法
    context.fillStyle = "#1424DE";
    context.strokeStyle = "#F5270B";
    context.strokeRect(610,10,190,190);
    context.fillRect(610,10,190,190);
</script>

 var canvas = document.getElementById("canvas");
    var context = canvas.getContext("2d");
    context.beginPath();
    //设置是个顶点的坐标，根据顶点制定路径
    for (var i = 0; i < 5; i++) {
        context.lineTo(Math.cos((18+i*72)/180*Math.PI)*200+200,
                        -Math.sin((18+i*72)/180*Math.PI)*200+200);
        context.lineTo(Math.cos((54+i*72)/180*Math.PI)*80+200,
                        -Math.sin((54+i*72)/180*Math.PI)*80+200);
    }
    context.closePath();
    //设置边框样式以及填充颜色
    context.lineWidth="3";
    context.fillStyle = "#F6F152";
    context.strokeStyle = "#F5270B";
    context.fill();
    context.stroke();

 var canvas = document.getElementById("canvas");
    var context = canvas.getContext("2d");
    //测试lineCap属性
    //设置基准线便于观察
    context.moveTo(10,10);
    context.lineTo(10,200);
    context.moveTo(200,10);
    context.lineTo(200,200);
    context.lineWidth="1";
    context.stroke();
    //butt
    context.beginPath();
    context.moveTo(10,50);
    context.lineTo(200,50);
    context.lineCap="butt";
    context.lineWidth="10";
    context.stroke();
    //round
    context.beginPath();
    context.moveTo(10,100);
    context.lineTo(200,100);
    context.lineCap="round";
    context.lineWidth="10";
    context.stroke();
    //square
    context.beginPath();
    context.moveTo(10,150);
    context.lineTo(200,150);
    context.lineCap="square";
    context.lineWidth="10";
    context.stroke();

    //测试linJoin属性
    //miter
    context.beginPath();
    context.moveTo(300,50);
    context.lineTo(450,100);
    context.lineTo(300,150);
    context.lineJoin="miter";
    context.lineWidth="10";
    context.stroke();
    //round
    context.beginPath();
    context.moveTo(400,50);
    context.lineTo(550,100);
    context.lineTo(400,150);
    context.lineJoin="round";
    context.lineWidth="10";
    context.stroke();
    //square
    context.beginPath();
    context.moveTo(500,50);
    context.lineTo(650,100);
    context.lineTo(500,150);
    context.lineJoin="bevel";
    context.lineWidth="10";
    context.stroke();

    //测试miterLimit属性
    context.beginPath();
    context.moveTo(700,50);
    context.lineTo(850,100);
    context.lineTo(700,150);
    context.lineJoin="miter";
    context.miterLimit="2";
    context.lineWidth="10";
    context.strokeStyle="#2913EC";
    context.stroke();

 var canvas = document.getElementById("canvas");
    var context = canvas.getContext("2d");

    //线性渐变
    var grd = context.createLinearGradient( 10 , 10, 100 , 350 );
    grd.addColorStop(0,"#1EF9F7");
    grd.addColorStop(0.25,"#FC0F31");
    grd.addColorStop(0.5,"#ECF811");
    grd.addColorStop(0.75,"#2F0AF1");
    grd.addColorStop(1,"#160303");
    context.fillStyle = grd;
    context.fillRect(10,10,100,350);

    //径向渐变
    var grd = context.createRadialGradient(325 , 200, 0 , 325 , 200 , 200 );
    grd.addColorStop(0,"#1EF9F7");
    grd.addColorStop(0.25,"#FC0F31");
    grd.addColorStop(0.5,"#ECF811");
    grd.addColorStop(0.75,"#2F0AF1");
    grd.addColorStop(1,"#160303");
    context.fillStyle = grd;
    context.fillRect(150,10,350,350);

    //位图填充
    var bgimg = new Image();
    bgimg.src = "background.jpg";
    bgimg.onload=function(){
        var pattern = context.createPattern(bgimg, "repeat");
        context.fillStyle = pattern;
        context.strokeStyle="#F20B0B";
        context.fillRect(600, 100, 200,200);
        context.strokeRect(600, 100, 200,200);
    };

  var canvas = document.getElementById("canvas");
    var context = canvas.getContext("2d");

    //translate()
    context.save();
    context.fillStyle = "#1424DE";
    context.translate(10,10);
    context.fillRect(0,0,200,200);
    context.restore();

    //scale()
    context.save();
    context.fillStyle = "#F5270B";
    context.scale(0.5,0.5);
    context.fillRect(500,50,200,200);
    context.restore();
    //rotate()

    context.save();
    context.fillStyle = "#18EB0F";
    context.rotate(Math.PI / 4);
    context.fillRect(300,10,200,200);
    context.restore();

     var canvas = document.getElementById("canvas");
    var context = canvas.getContext("2d");

    context.strokeStyle = "#F22D0D";
    context.lineWidth = "2";
    //绘制圆
    context.beginPath();
    context.arc(100,100,40,0,2*Math.PI);
    context.stroke();

    //绘制半圆
    context.beginPath();
    context.arc(200,100,40,0,Math.PI);
    context.stroke();

    //绘制半圆,逆时针
    context.beginPath();
    context.arc(300,100,40,0,Math.PI,true);
    context.stroke();

    //绘制封闭半圆
    context.beginPath();
    context.arc(400,100,40,0,Math.PI);
    context.closePath();
    context.stroke();

 function createRoundRect(context , x1 , y1 , width , height , radius)
    {
        // 移动到左上角
        context.moveTo(x1 + radius , y1);
        // 添加一条连接到右上角的线段
        context.lineTo(x1 + width - radius, y1);
        // 添加一段圆弧
        context.arcTo(x1 + width , y1, x1 + width, y1 + radius, radius);
        // 添加一条连接到右下角的线段
        context.lineTo(x1 + width, y1 + height - radius);
        // 添加一段圆弧
        context.arcTo(x1 + width, y1 + height , x1 + width - radius, y1 + height , radius);
        // 添加一条连接到左下角的线段
        context.lineTo(x1 + radius, y1 + height); 
        // 添加一段圆弧
        context.arcTo(x1, y1 + height , x1 , y1 + height - radius , radius);
        // 添加一条连接到左上角的线段
        context.lineTo(x1 , y1 + radius);
        // 添加一段圆弧
        context.arcTo(x1 , y1 , x1 + radius , y1 , radius);
        context.closePath();
    }
    // 获取canvas元素对应的DOM对象
    var canvas = document.getElementById('mc');
    // 获取在canvas上绘图的CanvasRenderingContext2D对象
    var context = canvas.getContext('2d');
    context.lineWidth = 3;
    context.strokeStyle = "#F9230B";
    createRoundRect(context , 30 , 30 , 400 , 200 , 50);
    context.stroke();

 var canvas = document.getElementById("canvas");
    var context = canvas.getContext("2d");

    context.font="bold 30px Arial"; //设置样式
    context.strokeStyle = "#1712F4";
    context.strokeText("欢迎来到我的博客！",30,100);

    context.font="bold 50px Arial"; 
    var grd = context.createLinearGradient( 30 , 200, 400 , 300 );//设置渐变填充样式
    grd.addColorStop(0,"#1EF9F7");
    grd.addColorStop(0.25,"#FC0F31");
    grd.addColorStop(0.5,"#ECF811");
    grd.addColorStop(0.75,"#2F0AF1");
    grd.addColorStop(1,"#160303");
    context.fillStyle = grd;
    context.fillText("欢迎来到我的博客！",30,200);

    context.save();
    context.moveTo(200,280);
    context.lineTo(200,420);
    context.stroke();
    context.font="bold 20px Arial"; 
    context.fillStyle = "#F80707";
    context.textAlign="left";
    context.fillText("文本在指定的位置开始",200,300);
    context.textAlign="center";
    context.fillText("文本的中心被放置在指定的位置",200,350);
    context.textAlign="right";
    context.fillText("文本在指定的位置结束",200,400);
    context.restore();

    context.save();
    context.moveTo(10,500);
    context.lineTo(500,500);
    context.stroke();
    context.fillStyle="#F60D0D";
    context.font="bold 20px Arial"; 
    context.textBaseline="top";
    context.fillText("指定位置在上面",10,500);
    context.textBaseline="bottom";
    context.fillText("指定位置在下面",150,500);
    context.textBaseline="middle";
    context.fillText("指定位置居中",300,500);
    context.restore();


    context.font="bold 40px Arial"; 
    context.strokeStyle = "#16F643";
    var text = "欢迎来到我的博客！";
    context.strokeText("欢迎来到我的博客！",10,600);
    context.strokeText("上面字符串的宽度为："+context.measureText(text).width,10,650);

 var canvas = document.getElementById("canvas");
    var context = canvas.getContext("2d");
    context.beginPath();
    //设置是个顶点的坐标，根据顶点制定路径
    for (var i = 0; i < 5; i++) {
        context.lineTo(Math.cos((18+i*72)/180*Math.PI)*200+200,
                        -Math.sin((18+i*72)/180*Math.PI)*200+200);
        context.lineTo(Math.cos((54+i*72)/180*Math.PI)*80+200,
                        -Math.sin((54+i*72)/180*Math.PI)*80+200);
    }
    context.closePath();
    //设置边框样式以及填充颜色
    context.lineWidth="3";
    context.fillStyle = "#F6F152";
    context.strokeStyle = "#F5270B";
    context.shadowColor = "#F7F2B4";
    context.shadowOffsetX = 30;
    context.shadowOffsetY = 30;
    context.shadowBlur = 2;
    context.fill();
    context.stroke();

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>图形组合</title>
    <style type="text/css">
        #canvas{
            border: 1px solid #1C0EFA;
            display: block;
            margin: 20px auto;
        }
        #buttons{
            width: 1000px;
            margin: 5px auto;
            clear:both;
        }
        #buttons a{
            font-size: 18px;
            display: block;
            float: left;
            margin-left: 20px;
        }
    </style>
</head>
<body>
    <canvas id="canvas" width="1000" height="800">
            你的浏览器还不支持canvas
    </canvas>
    <p id="buttons">
        <a href="#">source-over</a>
        <a href="#">source-atop</a>
        <a href="#">source-in</a>
        <a href="#">source-out</a>
        <a href="#">destination-over</a>
        <a href="#">destination-atop</a>
        <a href="#">destination-in</a>
        <a href="#">destination-out</a>
        <a href="#">lighter</a>
        <a href="#">copy</a>
        <a href="#">xor</a>
    </p>
</body>
<script type="text/javascript">

window.onload = function(){
    draw("source-over");

    var buttons = document.getElementById("buttons").getElementsByTagName("a");
    for (var i = 0; i < buttons.length; i++) {
        buttons[i].onclick = function(){
            draw(this.text);
            return false;
        };
    }
};

    function draw(compositeStyle){
        var canvas = document.getElementById("canvas");
        var context = canvas.getContext("2d");

        context.clearRect(0, 0, canvas.width, canvas.height);

        //draw title
        context.font = "bold 40px Arial";
        context.textAlign = "center";
        context.textBasedline = "middle";
        context.fillStyle = "#150E0E";
        context.fillText("globalCompositeOperation = "+compositeStyle, canvas.width/2, 60);

        //draw a rect
        context.fillStyle = "#F6082A";
        context.fillRect(300, 150, 500, 500);

        //draw a triangle
        context.globalCompositeOperation = compositeStyle;
        context.fillStyle = "#1611F5";
        context.beginPath();
        context.moveTo(700, 250);
        context.lineTo(1000,750);
        context.lineTo(400, 750);
        context.closePath();
        context.fill();
    }

</script>
</html>

var canvas = document.getElementById("canvas");
    var context = canvas.getContext("2d");

    context.beginPath();
    context.fillStyle = "#0C0101";
    context.fillRect(0,0,canvas.width,canvas.height);

    context.beginPath();
    context.fillStyle = "#FFFDFD";
    context.arc(400,400,100,0,2*Math.PI);
    context.fill();
    context.clip();

    context.beginPath();
    context.fillStyle = "#F60825";
    context.fillRect(200, 350, 400,50);

除了上述的属性的和方法，还有以下等方法：

drawImage()：向画布上绘制图像、画布或视频。

toDataURL() ：保存图形

isPointInPath()：如果指定的点位于当前路径中，则返回 true，否则返回 false。

这里就不逐个举例说明了。