javascript - Bad quality for 100% both width and height of canvas -

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i have done tiny example canvas, it's available on jsfiddle:

http://jsfiddle.net/yptr5/

<!doctype html> <html>     <head>     <title></title>     <style type="text/css">      html, body {         width: 100%;         height: 100%;         margin: 0px;         padding: 0px;     }      #mycanvas {         width: 100%;         height: 100%;         display: block;     }      </style>     </head>     <body>         <canvas id="mycanvas">             browser not support html5 canvas tag.         </canvas>         <script>              var canvas = document.getelementbyid( "mycanvas" );             var context = canvas.getcontext( "2d" );              context.id = "mycontext";             context.beginpath();             context.arc( 95, 50, 40, 0, 2 * math.pi );             context.stroke();              settimeout( function() {                  var rectwidth = 150;                 var rectheight = 75;                 context.fillstyle = "blue";                 context.fillrect( rectwidth / -2, rectheight / -2, rectwidth, rectheight );             }, 2000 );          </script>      </body> </html>

as able see, rendering result has low quality:

enter image description here

so, i'm wondering, how can draw various figures using canvas in quality, don't want draw in small size, want draw in 100% size of page.

so, maybe didn't define anti aliasing filter or else?

thanks!

problem

in general cases should avoid using css set canvas size.

the default size of canvas 300 x 150 pixels (bitmap). if set size using css we'll end scaling 300 x 150 pixels meaning browser start interpolating , smoothing image, why end blurry result.

solution

remove these css-rule:

#mycanvas {   /*width: 100%;   height: 100%;*/   display: block;   }

and set size in javascript this:

var canvas = document.getelementbyid( "mycanvas" );  canvas.width = window.innerwidth;     // equals window dimension canvas.height = window.innerheight;

you can of course set other size need (in pixels). want define position (i.e. fixed or absolute) canvas' css if goal full window size.

hope helps.


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