Dynamically resize canvas window with javascript/jquery?

Question

How can I resize a canvas with javascript/jquery?

Resizing using the css function and applying it to the canvas element just stretches the content as if you were stretching an image.

How would I go about doing this without the stretching?

http://jsfiddle.net/re8KU/4/

Answer 1

Make a function that does the drawing, then re-draw whenever something changes that requires it (like a page resize, etc). Try it out

Make sure you set the context.canvas.width/height, not CSS width/height. Also note that setting the size clears the canvas.

How I would write it:

(function(){
    var c = $("#canvas"), 
        ctx = c[0].getContext('2d');

    var draw = function(){
        ctx.fillStyle = "#000";
        ctx.fillRect(10,10,50,50);   
    };

    $(function(){
        // set width and height
         ctx.canvas.height = 600;
         ctx.canvas.width = 600;
        // draw
        draw();

        // wait 2 seconds, repeate same process
        setTimeout(function(){
            ctx.canvas.height = 400;
            ctx.canvas.width = 400;
            draw();
        }, 2000)
    });
})();

​

Answer 2

 (function($) {  
        $.fn.extend({  
            //Let the user resize the canvas to the size he/she wants  
            resizeCanvas:  function(w, h) {  
                var c = $(this)[0]  
                c.width = w;  
                c.height = h  
            }  
        })  
    })(jQuery)

Use this little function I created to take care of resizing on the go. Use it this way --

$("the canvas element id/class").resizeCanvas(desired width, desired height)

Answer 3

Whenever the browser is resized, the following solution resizes the dimensions of the canvas based on the dimensions of the window by creating an initial ratio.

Jsfiddle: http://jsfiddle.net/h6c3rxxf/9/

Note: The canvas needs to be re-drawn, when it is resized.

HTML:

<canvas id="myCanvas" width="300" height="300" >

CSS:

canvas {
    border: 1px dotted black;
    background: blue;
}

JavaScript:

(function() {
    // get the precentage of height and width  of the cavas based on the height and width of the window
    getPercentageOfWindow = function() {
        var viewportSize = getViewportSize();
        var canvasSize = getCanvastSize();
        return {
            x: canvasSize.width / (viewportSize.width - 10),
            y: canvasSize.height / (viewportSize.height - 10)
        };
    };
    //get the context of the canvas 
    getCanvasContext = function() {
        return $("#myCanvas")[0].getContext('2d');
    };
    // get viewport size
    getViewportSize = function() {
        return {
            height: window.innerHeight,
            width: window.innerWidth
        };
    };
    // get canvas size
    getCanvastSize = function() {
        var ctx = getCanvasContext();
        return {
            height: ctx.canvas.height,
            width: ctx.canvas.width
        };
    };
    // update canvas size
    updateSizes = function() {
        var viewportSize = getViewportSize();
        var ctx = getCanvasContext();
        ctx.canvas.height = viewportSize.height * percentage.y;
        ctx.canvas.width = viewportSize.width * percentage.x;
    };
    var percentage = getPercentageOfWindow();
    $(window).on('resize', function() {
        updateSizes();
    });
}());