Grid drawn using a <canvas> element looking stretched

Question

I'm trying to draw a grid on a <canvas> element with the ultimate goal of making a Go board.

For some reason the grid is looking stretched, with the lines being thicker than 1 pixel and the spacing being completely wrong. It doesn't even start in the (10,10) position..

It would be great if someone could take a look at tell me what I'm doing wrong.

http://jsfiddle.net/h2yJn/

Solution 1

I've found the problem. I was setting the dimensions of the <canvas> using CSS, when you actually have to set the width and height attributes. This was causing it to be stretched/skewed.

var canvas = $('<canvas/>').attr({width: cw, height: ch}).appendTo('body');

http://jsfiddle.net/h2yJn/66/

Solution 2

Please try it outside jsfiddle, maybe jsfiddle is applying some linear transformation.

Also please make sure that you add 0.5 everywhere to both x and y coordinates. Alternatively, you can apply translate(0.5, 0.5) to shift all coordinates by half a pixel.

Comments

[Acorn]

I'm getting the same result on jsbin.com, I'm pretty sure I've added 0.5px everywhere I could possibly add it. That wouldn't cause such dramatic effects anyway though would it?

[Aleksandr Kravets]

Another way is just to start a cycle from 0.5 like this: for (var i = 0.5; i < fieldSize+1; i+=40) {...