根据其他图像的位置将图像旋转90度

Question

I am trying to create a horizontal parallax website. I have an image with id #ellipse that slides on different positions from right to left, say -

item.screenPos=["320%","220%","120%","34%","-80%","-180%","-280%","-380%"];

When this image reaches to the position 34%, it is visible on the screen.

I want another image with id #strip (which is not sliding and is fixed at the center of the screen), to rotate by 90 degree when above image (with id #ellipse ) reaches at position 34%.

Currently i'm using this -

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script>   
$(document).ready(function(){
  $("#ellipse").position("34%")(function(){
    $("#strip").rotate({angle:90});
  });
}); 
</script>

Can anybody help me out. I am open to use javascript, jquery, css & php.

Answer 1

You need to use a library for parallax, or define an event that is fired as the parallax animation advances. For example, lets say your parallax animation will be controlled by the scroll position:

// catch the event that triggers the animation
// this could be a mouse position, a accelerometer angle, etc
$(window).scroll(function(){
    var currentScrollPosition = $(document).scrollTop(),
    // lets say your scroll animation should happen in the first 
    // 300px of scroll, therefore 0px = first frame of anim
    // 300px = last frame of anim
        animationPercentage = currentScrollPosition/300; // 0 to 1

    // only animate if in range
    if (animationPercentage <= 1){
        // now you can control stuff based on the percentage of the animation

        //                position = start pos + delta * %
        $('#ellipse').css('left', (-380 +  (320 + 380) * animationPercentage );

        // rotate as a function of animationPercentage
        // let's say that #ellipse is visible at 50% of the animation
        if (animationPercentage >= 0.5){
            $('#strip').css('-webkit-transform', 'rotate(90deg)');  // or
            $('#strip').addClass('rotate');
        }
    }
});

Now if the position is not proportional to the animation event you could do something like this:

item.screenPos={
    "0.9":"320%", // position at 90% of animation
    "0.85":"220%", // position at 85% of animation
    "0.71":"120%", //... you get the point
    "0.5":"34%",
    "0.48":"-80%",
    "0.2":"-180%",
    "0.15":"-280%",
    "0":"-380%"
};

And match the animationPercentage to the key of each value. But that I believe you can give it a shot on your own.