How to draw Font Awesome Icons onto html canvas [Version <5]

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How can I draw Font Awesome characters (Icons Glyphs) onto html5 canvas? I am using an older version of Font Awesome.

How can I style those drawn characters?

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2条回答

无人共我

2020-12-03 12:06

Here's how to draw Font Awsome glyphs on html5 canvas:

Link in Font Awesome:

<link rel="stylesheet" 
    href="https://maxcdn.bootstrapcdn.com/font-awesome/4.5.0/css/font-awesome.min.css">

Set the context font to Font Awesome:

// set the canvas context's font-size and font-face
context.font='14px FontAwesome';

Draw one of the Font Awesome characters on the canvas:

// specify the desired character code with the Unicode prefix (\u) 
context.fillText('\uF047',20,50);

Here's example code and a Demo:

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

ctx.font='12px verdana';
ctx.fillText('Please wait for Font Awesome to load...',20,30);

// give font awesome time to load
setTimeout(start,2000);

function start(){
  ctx.clearRect(0,0,canvas.width,canvas.height);
  ctx.font='30px FontAwesome';
  ctx.fillText('\uF047',20,50);
}

body{ background-color: ivory; }
#canvas{border:1px solid red; margin:0 auto; }

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.5.0/css/font-awesome.min.css">
<script src="https://code.jquery.com/jquery-2.1.1.min.js"></script>
<h4>Font Awesome glyph drawn onto html5 canvas</h4>
<canvas id="canvas" width=300 height=100></canvas>

[Addition: another way to load FontAwesome]

And as @Kaiido comments, you can cause the browser to start loading FontAwesome by setting the font-family:fontawesome on the canvas element (or another element).

The demo shows how to load custom fonts (including FontAwesome) "on-the-fly".

[Addition: A FontAwesome onload function]

Like img's, fonts load asynchronously so you must wait for them to fully load before trying to draw with them on canvas. But unlike imgs, fonts don't have a built-in .onload method to tell us when they are fully loaded.

Here's a workaround onload function you can use to trigger a callback when FontAwesome has fully loaded and is ready to fillText on the canvas:

<!doctype html>
<html>
<head>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.5.0/css/font-awesome.min.css">
<script src="https://code.jquery.com/jquery-2.1.1.min.js"></script>
<style>
    body{ background-color: ivory; }
    #canvas{border:1px solid red; margin:0 auto; }
</style>
<script>
$(function(){

    var canvas=document.getElementById("canvas");
    var ctx=canvas.getContext("2d");
    var cw,ch;

    AwesomeFontOnload(start,3000);

    function start(){
        ctx.font='48px fontawesome';
        ctx.fillText('\uF064\uF065 \uF0a5',20,75);
    }

    function AwesomeFontOnload(callback,failAfterMS){
        var c=document.createElement("canvas");
        var cctx=c.getContext("2d");
        var ccw,cch;
        var fontsize=36;
        var testCharacter='\uF047';
        ccw=c.width=fontsize*1.5;
        cch=c.height=fontsize*1.5;
        cctx.font=fontsize+'px fontawesome';
        cctx.textAlign='center';
        cctx.textBaseline='middle';
        var startCount=pixcount();
        var t1=performance.now();
        var failtime=t1+failAfterMS;
        //
        requestAnimationFrame(fontOnload);
        //
        function fontOnload(time){
            var currentCount=pixcount();
            if(time>failtime){
                alert('Font Awsome failed to load after '+failAfterMS+'ms.');
            }else if(currentCount==startCount){
                requestAnimationFrame(fontOnload);
            }else{
                callback();
            }
        }
        //
        function pixcount(){
            cctx.clearRect(0,0,ccw,cch);
            cctx.fillText(testCharacter,ccw/2,cch/2);
            var data=cctx.getImageData(0,0,ccw,cch).data;
            var count=0;
            for(var i=3;i<data.length;i+=4){
                if(data[i]>10){count++;}
            }
            return(count);
        }
    }

}); // end $(function(){});
</script>
</head>
<body>
    <h4>Font Awesome glyphs drawn onto html5 canvas</h4>
    <canvas id="canvas" width=300 height=300></canvas>
</body>
</html>

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青春惊慌失措

2020-12-03 12:26
how to use font icons (Font Awesome) in html canvas

you can inspect the fontawsome .css file and get what code has been used for each icon.

For Eg: If you see the file for the code used to get the icon fa-info-circle, its as below
```
.fa-info-circle:before {
  content: "\f05a";
}
```
So try context.font = '\uf05a'; // this will give you fa-info-circle. And remember to add the \u before the code. Also you need to mention the font family as FontAWsome
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