html canvas text size not accurate
I am trying to center text in a box, but the ctx.measureText() is not returning accurate values. When the below code is run, the text is not accurately centered. It runs for me under google chrome, but I couldn't get it to run under jsfiddle (sorry)
<html>
<head>
<script type="text/javascript">
function writeText(){
canvas=document.getElementById('canvas');
ctx = canvas.getContext('2d');
ctx.fillStyle='rgb(250,0,0)'; //red box
ctx.fillRect(100,100,300,300); //box of size 200x200 drawn at (100,100)
ctx.fillStyle='rgb(0,250,0)';
yOff=0;
for (var i=0;i<4;i++){
text="Hello World";
size=20+i*10
font='bold '+size+'px serif';
ctx.font=font;
ctx.textBaseline='top';
width=ctx.measureText(font,text).width;
height=size;
x=100+(300-width)/2; //draw inside the rectangle of 100x100 at pos (0,0)
y=(300-height)/2+yOff; //draw inside the rectangle of 100x100 at pos (0,0)
ctx.fillText(text,x,y);
yOff+=50
}
}
</script>
</head>
<body onload="writeText();" bgcolor="yellow">
<canvas name="canvas" id="canvas" wi开发者_运维技巧dth="500" height="500"></canvas>
</body>
</html>
You are accidentally measuring the font string instead of text each time!
measureText has only one argument and you are giving it two. It should just be
width = ctx.measureText(text).width;
Here it is in jsfiddle:
http://jsfiddle.net/PtSAf/19/
加载中,请稍侯......
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