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Summary of methods to achieve text alignment in HTML5 Canvas

不言Original: 2018-06-05 15:58:382901browse

This article mainly introduces a summary of the methods to achieve text alignment in HTML5 Canvas, including the use of horizontally aligned context.textAlign and vertically aligned context.textBaseline and various parameters. Friends in need can refer to the following

Horizontal alignment textAlign

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

The values and meanings are as follows surface.

<!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>

Value	Description
start	Default. The text starts at the specified position.
end	The text ends at the specified position.
center	The center of the text is placed at the specified location.
left	The text is aligned left,
right	The text is aligned right.

Let’s feel it intuitively through an example.

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<!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>   
<div id="canvas-warp">   
    <canvas id="canvas">   
        你的浏览器居然不支持Canvas？！赶快换一个吧！！   
    </canvas>   
</div>   
  
<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>

Run result:

2016324114332033.jpg (850×500)

Vertical alignment textBaseline

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

The values and meanings are as follows surface.

Value	Description
alphabetic	Default. Text baselines are ordinary letter baselines.
top	The text baseline is the top of the em box.
hanging	The text baseline is the hanging baseline.
middle	The text baseline is the center of the em box.
ideographic	The textual baseline is the ideographic baseline.
bottom	The text baseline is the bottom of the em box.

#First, let’s look at the positions represented by each baseline through a picture.
2016324114358024.gif (600×268)

Let’s feel it intuitively through an example.

JavaScript CodeCopy content to clipboard

<!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>

Run result:

Related recommendations:

HTML5 canvas basic drawing drawing lines

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