CODEWITHSUNDEEP
htmlcanvas
Likhit
Likhit

Reputation: 809

Canvas not working as intended

I was trying a script to draw graph paper like grids on the canvas from dive into html5. The result is supposed to draw a mesh with squares of side 10px but i'm getting the size as approximately 20px, and not exact squares.
Here is the code,`

   <html>
      <head>     
           <style>
    body{
        margin: 20px 20px 20px 20px;
    }

    canvas{
        width: 500px;
        height: 375px;
        border: 1px solid #000;
    }
    </style>
    <script type="text/javascript">
        function activate(){
            var canvas =document.getElementById("exp");
            var context = canvas.getContext("2d");

            for (var x=0.5;x<500;x+=10){
                context.moveTo(x,0);
                context.lineTo(x,375);
                console.log(x);
            }

            for (var y=0.5;y<375;y+=10){
                context.moveTo(0,y);
                context.lineTo(500,y);
            }

            context.strokeStyle="#000";
            context.stroke();
        }
    </script>
</head>

<body>
    <canvas id="exp"><script type="text/javascript">activate();</script></canvas>
</body
     </html>

And this is the output:
canvas rendered
while the actual output should be:
actual canvas
Note: i'm not worried about the color difference. what i don't understand is why the space between 2 lines is ~20px(as checked by a measurement tool on firefox) instead of 10px.
Also, on printing the values of x, it gives the right value(i.e. incremented by 10 each time).

Upvotes: 0

Views: 1569

Answers (2)

scessor
scessor

Reputation: 16125

Javascript can calculate for you. Only set the parameters:

html:

<canvas id="exp"></canvas>

js:

function activate(id, xcount, ycount, width, color) {
    var canvas = document.getElementById(id);
    var context = canvas.getContext("2d");

    canvas.width = xcount * width + 1;
    canvas.height = ycount * width + 1;

    for (var x = 0.5; x < canvas.width; x += width) {
        context.moveTo(x, 0);
        context.lineTo(x, canvas.height);
    }

    for (var y = 0.5; y < canvas.height; y += width) {
        context.moveTo(0, y);
        context.lineTo(canvas.width, y);
    }

    context.strokeStyle = color;
    context.stroke();
}
activate("exp", 37, 50, 10, "#ccc");

Also see this example.

Upvotes: 0

Kevin
Kevin

Reputation: 1157

you can not set the canvas' size with css you should set in the DOM's attribute.

<canvas width="100" height="200"></canvas>

Upvotes: 2

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