(SO - 22049177) Reveal part of transparent overlayed image where mouse is hovered

by Jessel John

HTML

<br/><br/><br/>
<div id="container">
    <div class="blurPic"></div>
    <img src="http://i.imgur.com/IGKVr8r.png" alt="follow picture" />
</div>

CSS

html,body{
    margin:0px;
    padding:0px;
}
#container{
    position:relative;
    margin-left:100px;
}
.blurPic{
    position:absolute;
    top:0px;
    left:0px;
    width:0px;
    height:0px;
    box-shadow:0px 0px 0px 160px white inset; 
    -moz-box-shadow:0px 0px 0px 160px white inset; 
    -webkit-box-shadow:0px 0px 0px 160px white inset; 
    -ms-box-shadow:0px 0px 0px 160px white inset; 
    opacity:0.9;
    filter:alpha(opacity=0.9); /* For IE8 and earlier */
}

JavaScript

/**Give equal width and height as <img> to .blurPic**/
var hgt = $('.blurPic').width($('#container img').width());
$('.blurPic').height($('#container img').height());
/*****************************************************/

/*******Get shadow values*****/
var result = $('.blurPic').css('boxShadow').match(/(-?\d+px)|(rgb\(.+\))/g)
var color = result[0],
    y = result[1],
    x = result[2],
    blur = result[3];
/******************************/

/**Change box-shadow on mousemove over image**/
var blurStartW = hgt.width()/2;
var blurStartH = hgt.height()/2;
$('.blurPic').mousemove(function(event){
    event.preventDefault();
    var scrollLeftPos = $(window).scrollLeft(),
    scrollTopPos = $(window).scrollTop(),
    offsetLft = hgt.offset().left,
    offsetTp = hgt.offset().top;
    var upX=event.clientX;
    var upY=event.clientY;
    $(this).css({boxShadow : ''+(-offsetLft+upX-blurStartW+scrollLeftPos)+'px '+(-offsetTp+upY-blurStartH+scrollTopPos)+'px 20px 100px white inset'});
});
/*********************************************/

/***reset box-shadow on mouseout***/
$('.blurPic').mouseout(function(){
    $(this).css({boxShadow : '0px 0px 0px 160px white inset'});
});
/**********************************/