Rotate rectangular canvas image to fit

wbt11a

I'm trying to rotate an image that fills a rectangle canvas element. Using the code below, I can rotate satisfactorily (in 90 degree increments). However, when converting large faces to small faces, I can't figure out how to fill the entire canvas. Instead, I have a compressed image. Any help would be greatly appreciated in solving this problem. Thanks!

So far I have:

var degrees = 90;

function drawRotated(degrees){


    var canvas = document.getElementById('myCanvas');

    var ctx = canvas.getContext('2d');


    ctx.setTransform(1,0,0,1,0,0);
    ctx.clearRect(0, 0, canvas.width, canvas.height);
    var translateX = (canvas.width)/2;
    var translateY = (canvas.height)/2;
    ctx.translate(translateX,translateY);
    ctx.rotate(degrees*Math.PI/180);
    ctx.translate(-translateX,-translateY);
    ctx.drawImage(theImage, 0,0, canvas.width, canvas.height);

}
Dream Lab

To rotate an image without distorting it, be sure to convert the image to 0, 0. This will bring the center of the image to the origin. You are the matrix around the rotateorigin ( 0, 0) . You are rotating around the center of the canvas.

Also, you have to do some math for one translation so that the image is always in the top left corner.

function drawRotated(degrees){
    var theImage = document.getElementById('image');
    var imageWidth = theImage.naturalWidth;
    var imageHeight = theImage.naturalHeight;

    var canvas = document.getElementById('myCanvas');
    var ctx = canvas.getContext('2d');

    var angle = degrees*Math.PI/180;

    ctx.clearRect(0, 0, canvas.width, canvas.height);

    // this will align your image in the upper left corner when rotating in 90deg increments
    ctx.translate(Math.abs(imageWidth/2 * Math.cos(angle) + imageHeight/2 * Math.sin(angle)), Math.abs(imageHeight/2 * Math.cos(angle) + imageWidth/2 * Math.sin(angle)));
    ctx.rotate(angle);
    ctx.translate(-imageWidth/2, -imageHeight/2);
    ctx.drawImage(theImage, 0, 0);
}

see FIDDLE

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