Question

<style type="text/css">

@-webkit-keyframes waveArm{
    0%,100% {
        -webkit-transform:rotate(0deg);
    }
    10%,30%,50%,70%,90% {
        -webkit-transform:rotate(90deg);
    }
    20%,40%,60%,80% {
        -webkit-transform:rotate(45deg);
        }
}

#arm {
    position:absolute;
    top:135px;
    left:135px;
    width:201px;
    height:74px;
    background:url(test-arm.png) 0 0 no-repeat;
    -webkit-animation: waveArm 3s 1s 1;
    -webkit-transform-origin:81% 46%;
}

</style>

<div id="arm"></div>

I would like to know if there is way to calculate the transform-orgin X and Y values using the height and width of an object so that it pivots around a single point smoothly like an arm and shoulder waving.

In this case i figured it out to be 81% and 46% through trial and error but would like a simpler method.

Thanks

Answer 1

Aaah! Figured it out in px. Easy really!

The width of the arm is 201px and the height is 74px.
The pivot point i needed is 34px from the top and 34px from the right.

X starts from the left. Y starts from the top so…
X = 201-34 = 167

Y = 34

-webkit-transform-origin:167px 34px;