Hairline gaps between items in isotope-packery on window resize

Question

I am having a small issue with my isotope-packery layouts, where a very thin 1px or less line is appearing between certain items at some window sizes. Is there a way to eliminate this hairline gap?

Example: http://i.imgur.com/6jkqhZw.png (look between items 3 and 4)

I have a JSFiddle here to look at: http://jsfiddle.net/drawcard/akw6m9x1/ (resize the fiddle "window", so you can see the gaps)

// external js:
// http://isotope.metafizzy.co/beta/isotope.pkgd.js

//packery js (no need to copy this over if you have it included)
/*!
 * Packery layout mode PACKAGED v1.1.0
 * sub-classes Packery
 * http://packery.metafizzy.co
 */

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//Site Code
$( function() {
  $('.container').isotope({
    itemSelector: '.item',
    layoutMode: 'packery',
    cellsByRow: {
      columnWidth: '.grid-sizer'
    }
  });
});

$(window).load(function(){
    $('.container').isotope('layout');
})

.container { margin-top: 2em; margin-bottom: 2em; width: 100%; /*background-color:#ff9900;*/}

/* clear fix */ 
.container:after { content: ''; display: block; clear: both; }

.item, .grid-sizer { width: 50%; height:0; padding-bottom:50%; opacity:0.6 position:relative; box-sizing:border-box;}
.item img {max-width:100%;height:auto;position:absolute;top:0;right:0;bottom:0;left:0;}
.big {width:100%; height:0; padding-bottom:100%;}
.item:before{content:'';padding-top:50%;display:block;}
.item .contents{position:absolute;top:0;right:0;bottom:0;left:0;opacity:0.6; padding:20px;}

/*styling items so we can see them in demo*/
.item:nth-child(odd) .contents{background-color:#ccc}
.item:nth-child(even) .contents{background-color:#aaa}

@media (min-width: 480px) { 
    .grid-sizer, .item {width: 25%; height: 0; padding-bottom:25%;}   
    .big {width: 50%; height: 0; padding-bottom:50%;}   
}

@media (min-width: 768px) { 
    .grid-sizer, .item {width: 12.5%; height: 0; padding-bottom:12.5%;} 
    .big {width: 25%; height: 0; padding-bottom:25%;}   
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<h1>Isotope - masonry element sizing columnWidth</h1>

<div class="container">
  <div class="grid-sizer"></div>
    <div class="item">
        <img src="http://lorempixel.com/512/512/cats/1" />
        <div class="contents">
            <h2>1</h2>
        </div>
    </div>
        <div class="item big">
            <img src="http://lorempixel.com/512/512/cats/2" />
        <div class="contents">
            <h2>2</h2>
        </div>
    </div>
        <div class="item">
            <img src="http://lorempixel.com/512/512/cats/3" />
        <div class="contents">
            <h2>3</h2>
        </div>
    </div>
        <div class="item">
            <img src="http://lorempixel.com/512/512/cats/4" />
        <div class="contents">
            <h2>4</h2>
        </div>
    </div>
        <div class="item">
            <img src="http://lorempixel.com/512/512/cats/5" />
        <div class="contents">
            <h2>5</h2>
        </div>
    </div>
        <div class="item big">
            <img src="http://lorempixel.com/512/512/cats/6" />
        <div class="contents">
            <h2>6</h2>
        </div>
    </div>
        <div class="item big">
            <img src="http://lorempixel.com/512/512/cats/7" />
        <div class="contents">
            <h2>7</h2>
        </div>
    </div>
        <div class="item">
            <img src="http://lorempixel.com/512/512/cats/8" />
        <div class="contents">
            <h2>8</h2>
        </div>
    </div>
        <div class="item">
            <img src="http://lorempixel.com/512/512/cats/9" />
        <div class="contents">
            <h2>9</h2>
        </div>
    </div>
        <div class="item big">
            <img src="http://lorempixel.com/512/512/cats/10" />
        <div class="contents">
            <h2>10</h2>
        </div>
    </div>
</div>

Answer 1

@Phpdevpad suggested I define dimensions for the image, however if I put the dimensions in the picture she'd be locked. My solution was to put the image as the background from itemSelector and define a fixed height for the itemSelector.

Answer 2

As far as I can tell from developer console, Isotope positions the items with an absolute position and absolute left and top pixel values, which sometimes appears to be one pixel off. That seems to be a bug with Isotope.

I suggest you'd report that as a bug here: https://github.com/metafizzy/isotope/issues