Resizing and cropping an image in HTML5 and css

Question

My requirements -

1. A random image gets displayed inside div/canvas
2. Image height should get adjusted to parent height
3. Image width should get re-sized proportionately (with height)
4. If image width is more than parent width, crop from left and right equally

I have achieved this with java script. Jsfiddle is at http://jsfiddle.net/yesprasoon/N3WvF/. You can resize the output window to see how it is working.

However I feel that I am doing it tedious way and there is something very simple in CSS and/or jQuery. could you please help me with pure css (preferably)?

I am attaching java script here as well -

var strDataURI;
//
displayBackground(true);
//
window.onresize = function(event) {
 displayBackground(false);
}
//
function displayBackground(bChangeImage)
{
 //alert("displayBackground");
 var appWidth = window.innerWidth;
 var appHeight = window.innerHeight;
 //
 if (bChangeImage)
 {
   var suffix_array = ["_california","_easter","_eiffel","_hk","_taj"];
   var ran = Math.floor((Math.random()*5)+1);
   ran = ran - 1;
   //ran = 3;
   strDataURI = "http://minds-eye.info/TP_Test/TP"+suffix_array[ran]+".jpg";
 }
 //
 var myCanvas = document.getElementById('canvas');
 var ctx = myCanvas.getContext('2d');
 var img = new Image;
 img.onload = function(){
  ctx.canvas.width  = appWidth;
  ctx.canvas.height = appHeight;
  //
  var hFraction = appHeight / img.naturalHeight;
  var displayWidth = img.naturalWidth*hFraction;
  mrgLeft = (appWidth - displayWidth)/2;
  mrgTop = (appHeight - img.naturalHeight)/2;
  ctx.drawImage(img,mrgLeft,0, displayWidth, appHeight);
  //blurMargin = 20;
  //stackBlurCanvasRGB( "canvas", blurMargin, blurMargin, appWidth-blurMargin*2, appHeight-blurMargin*2, 6 );
  };
 img.src = strDataURI;
 }

Answer 1

This should do the trick :

FIDDLE

HTML:

<div id="canvasHolder">
</div>

CSS

#canvasHolder{
    background: white url(http://placekitten.com/400/700) no-repeat center center;
    background-size: auto 100% ;
    height:100%;
    width:100%;
}

Answer 2

To have the height of a background image always keep to 100% of the containing element and the width automatically scale, keeping the ratio, just set the background-size to "auto 100%" so that the width is set to auto and the height to 100%. The width will scale proportionately while the height always stays at 100% of the containing element's height.

The centering provides the automatic cropping left and right.

HTML:

  <div class="container">       
  </div>

CSS:

.container {
  background-image: url(https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcQWamCIidr9XrdW7BqKL5DXbqqQxlL8z43Imawqvi5esIqNe7Uh);
  background-size: auto 100%;
  background-repeat: no-repeat;
  background-position: center;
  height: 300px;
}

See my jsBiin demo here. Change the height of the container in the CSS to see the image automatically scale proportionately.