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Code summary for text alignment in HTML5 Canvas

黄舟Original: 2017-03-14 16:00:242272browse

This article mainly introduces the HTML5 Canvas summary of methods to achieve text alignment, including the use of horizontally aligned context.textAlign and vertically aligned context.textBaseline and their respective Friends who need it can refer to the following

Horizontal alignment textAlign

context.textAlign="center|end|left|right|start";

The values and meanings are as follows.

##ValueDescriptionstartdefault. The text starts at the specified position. endThe text ends at the specified position. centerThe center of the text is placed at the specified location. leftThe text is aligned left, rightThe text is aligned right.

Let’s feel it intuitively through an example.

<!DOCTYPE html>   
<html lang="zh">   
<head>   
    <meta charset="UTF-8">   
    <title>textAlign</title>   
    <style>   
        body { background: url("./images/bg3.jpg") repeat; } 
        #canvas { border: 1px solid #aaaaaa; display: block; margin: 50px auto; }   
    </style>   
</head>   
<body>   
<p id="canvas-warp">   
    <canvas id="canvas">   
        你的浏览器居然不支持Canvas？！赶快换一个吧！！   
    </canvas>   
</p>   
  
<script>   
    window.onload = function(){   
        var canvas = document.getElementById("canvas");   
        canvas.width = 800;   
        canvas.height = 600;   
        var context = canvas.getContext("2d");   
        context.fillStyle = "#FFF";   
        context.fillRect(0,0,800,600);   
  
        // 在位置 400 创建蓝线   
        context.strokeStyle="blue";   
        context.moveTo(400,100);   
        context.lineTo(400,500);   
        context.stroke();   
  
  
        context.fillStyle = "#000";   
        context.font="50px Arial";   
  
        // 显示不同的 textAlign 值   
        context.textAlign="start";   
        context.fillText("textAlign=start", 400, 120);   
        context.textAlign="end";   
        context.fillText("textAlign=end", 400, 200);   
        context.textAlign="left";   
        context.fillText("textAlign=left", 400, 280);   
        context.textAlign="center";   
        context.fillText("textAlign=center", 400, 360);   
        context.textAlign="right";   
        context.fillText("textAlign=right", 400, 480);   
    };   
</script>   
</body>   
</html>

##Running result:

Code summary for text alignment in HTML5 Canvas

Vertically align textBaseline

context.textBaseline="alphabetic|top|hanging|middle|ideographic|bottom";

##ValueDescriptionalphabeticdefault. Text baselines are ordinary letter baselines. topThe text baseline is the top of the em box. hangingThe text baseline is the hanging baseline. middleThe text baseline is the center of the em box. ideographicThe textual baseline is the ideographic baseline. bottomThe text baseline is the bottom of the em box. #First, let’s look at the positions represented by each baseline through a picture.

Let’s use an example to intuitively feel it. Code summary for text alignment in HTML5 Canvas

<!DOCTYPE html>   
<html lang="zh">   
<head>   
    <meta charset="UTF-8">   
    <title>textBaseline</title>   
    <style>   
        body { background: url("./images/bg3.jpg") repeat; } 
        #canvas { border: 1px solid #aaaaaa; display: block; margin: 50px auto; }   
    </style>   
</head>   
<body>   
<p id="canvas-warp">   
    <canvas id="canvas">   
        你的浏览器居然不支持Canvas？！赶快换一个吧！！   
    </canvas>   
</p>   
  
<script>   
    window.onload = function(){   
        var canvas = document.getElementById("canvas");   
        canvas.width = 800;   
        canvas.height = 600;   
        var context = canvas.getContext("2d");   
        context.fillStyle = "#FFF";   
        context.fillRect(0,0,800,600);   
  
        //在位置 y=300 绘制蓝色线条   
        context.strokeStyle="blue";   
        context.moveTo(0,300);   
        context.lineTo(800,300);   
        context.stroke();   
  
        context.fillStyle = "#00AAAA";   
        context.font="20px Arial";   
  
        //在 y=300 以不同的 textBaseline 值放置每个单词   
        context.textBaseline="top";   
        context.fillText("Top",150,300);   
        context.textBaseline="bottom";   
        context.fillText("Bottom",250,300);   
        context.textBaseline="middle";   
        context.fillText("Middle",350,300);   
        context.textBaseline="alphabetic";   
        context.fillText("Alphabetic",450,300);   
        context.textBaseline="hanging";   
        context.fillText("Hanging",550,300);   
    };   
</script>   
</body>   
</html>

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