A jQuery responsive image plugin with viewport or container based width matching support
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README.md

jQuery Responsive Image Plugin

A jQuery responsive image plugin with viewport or container width matching support. Just load image by sizes you really need, save lots of bandwidth and make the world a better place :)

This plugin doesn't need any matchMedia polyfills or shims for unknown html elements.

Usage

Load scripts and initialize the responsive images.

<!-- jQuery >1.7.2 is required -->
<script src="js/jquery.min.js"></script>
<script src="../build/jquery.responsiveImage.min.js"></script>
<script>
    $(document).ready(function () {
        $('.picture').responsiveImage();
    });
</script>

Default image markup:

<span class="picture">
    <!-- optional fallback <img>: if JS is disabled or image is not loading while preload option is set to 'true' no image tag will be rendered. To make sure that an <img> tag is rendered set it as a fallback within the html. -->
    <img src="small.jpg" title="" alt="">
    <span data-src="small.jpg"></span>
    <span data-src="medium.jpg" data-min-width="600"></span>
    <span data-src="large.jpg" data-min-width="1000"></span>
</span>

you will get:

<!-- Viewport Width: 0px - 599px -->
<span class="picture">
    <img src="small.jpg" alt=""/>    
</span>

<!-- Viewport Width: 600px - 999px -->
<span class="picture">
    <img src="medium.jpg" alt=""/>    
</span>

<!-- Viewport Width: >1000px -->
<span class="picture">
    <img src="large.jpg" alt=""/>    
</span>

Options

source (default: > span)

The jQuery selector for source elements.

sourcePrefix (default: '')

A prefix for every(!) source element. Might be the default URL to the asset folder or a CDN so the source element only needs the relative path to the specific image.

This parameter can also be set with a data-source-prefix attribute directly on the picture wrapper.

container (default: null)

A default container element that defines the size for the responsive image to be loaded. The element will be selected with jQuery's .parents(container) function.

This parameter can also be set with a data-container attribute directly on the picture wrapper. Setting this parameter is recommended because it optimizes the target size for the responsive image and therefor traffic bandwidth.

<figure>
    <span class="picture" data-container="figure">
        <!-- responsive image sources -->
    </span>
</figure>

resizeEvent (default: resize)

This is the resize event used to detect the resize of the viewport. You can set any event that can be used inside jQuery's .on() function. Set resizeEvent to empty string to disable image calculation on resize.

It defaults to the resize event, which is not recommended because of the high amount of fired events.

You can use my debounced width resize event plugin debouncedwidth to reduce the amount of fired events: https://github.com/janrembold/jquery-debouncedwidth

minWidthDefault (default: 0)

The minimum width that is used, if no data-min-width was set. That might be helpful if you don't want to show images below a specific width. Be patient, this value can be overridden by data-min-width values that are smaller than the minWidthDefault value.

maxWidthDefault (default: Number.MAX_VALUE)

The maximum width that is used, if no data-max-width was set. That might be helpful if you don't want to show images above a specific width. Be patient, this value can be overridden by data-max-width values that are smaller than the maxWidthDefault value.

minDprDefault (default: 1)

The minimum device pixel ratio that is used if no data-min-dpr was set. Changing this value is not recommended. If you want to show only Retina images set this value to 2

attributes (default: ['title', 'alt', 'class', 'width', 'height'])

These attributes are set to the generated responsive image tag. See Attributes-Section below for detailed information.

preload (default: false)

Preload images before loading them into the DOM. Default is immediate loading of images.

autoDpr (default: false)

Automatically include dpr on best fit width calculation.
If enabled this adds retina support by default without the need for data-min-dpr attributes.

onGetWidth (default: null)

By default the viewport or container width are calculated automatically. This callback function can be used for any custom width calculation. Inside this function you can use the plugins' context.

onGetWidth: function(){
    // this.$container is the jQuery object used for container 
    // this.options are the plugins' options
    return 123; // custom integer width
}

onLoadSources (default: null)

This callback function can be used to completely overwrite the source loading process.

onLoadSources: function( context ){
    // "context" gives full access to the plugins context
    
    // Following source shows a default source object. This structure is required!
    // var source = {
    //    'src':      context.options.sourcePrefix + $source.data('src'),
    //    'minWidth': $source.data('min-width') || context.options.minWidthDefault,
    //    'maxWidth': $source.data('max-width') || context.options.maxWidthDefault,
    //    'minDpr':   $source.data('min-dpr') || context.options.minDprDefault
    // };
    
    // Add other image attributes to source object as needed, e.g. "class", "title" .... 
    
    return [ /* array of sources */ ]; 
}

Events fired by the plugin

These events get fired:

Event Description Element
ready.responsiveImage This event fires when the responsive image was initially loaded, fires only once The picture container
all.ready.responsiveImage This event fires when all responsive images were initially loaded, fires only once Global - $(window)
new.source.responsiveImage This event fires when the image was inserted into the DOM The picture container
load.source.responsiveImage This event fires when the image source was loaded The picture container

Event Listeners

Event Description Element
load.responsiveImage This event triggers the responsive image load method and forces a recalculation of the currently used image The picture container

Attributes

Following image attributes can be set with there corresponding data attributes.

  • alt with data-alt
  • title with data-title
  • class with data-class
  • width with data-width
  • height with data-height

You can set these attributes globally on the parent tag or individually on the images source tag. The image source tag overrides the global attribute.