css3 rotate image preserving its left top position

Question

I have an image which width and height can vary. I want to be able to rotate image preserving initial top and left positions. I'm using transform: rotate(270deg); The problem is that the image is moving to the left. I know that transform-origin css property can solve the issue, but how to calculate the top left values for this property? Maybe there is a formula for that? Here is the example showing that image is moved to the left from the initial left position. http://jsfiddle.net/h48ca/2/

<img src="https://dl.dropboxusercontent.com/u/31490359/e001420737da443b0fb75abfaddc5f22.jpg" style="transform: rotate(270deg); -webkit-transform: rotate(270deg); -ms-transform:rotate(270deg);">

Answer 1

This is the rotation - Rotate animation

note : size of image has been modified because of better visibility!

html

<img src="https://dl.dropboxusercontent.com/u/31490359/e001420737da443b0fb75abfaddc5f22.jpg">

css

img{
    width:40%;
    height:auto;
    position:absolute;
    top:100px;
    left:50px;
    transition:all 2s ease;
}

img:hover {
    transform: rotate(270deg);
    -webkit-transform: rotate(270deg);
    -ms-transform:rotate(270deg);
}