/*!
* JqueryAsynchImageLoader (JAIL) : plugin for jQuery
*
* Developed by
* Sebastiano Armeli-Battana (@sebarmeli) - http://www.sebastianoarmelibattana.com
* Dual licensed under the MIT or GPL Version 3 licenses.
*/
/*
Copyright (c) 2011 Sebastiano Armeli-Battana (http://www.sebastianoarmelibattana.com)
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see .
*/
/* JAIL helps loading images asynchronously and it can be used to make your page load faster.
* Selected images will be downloaded after the document is ready not blocking the page
* to render other elements. Images can be loaded after an event is triggered (like clicking
* on a link, mouseovering on some elements, scrolling up/down) or after some delay or simply the
* visible images will be loaded.
*
* First of all, this plugin requires you to make some HTML changes.
* E.g.
*
*
* You can define a noscript block in order to respect the principles of progressive
* enhancemnt
* E.g.
*
*
* You can call the function in this way
* E.g.
* $(function(){
* $('img.lazy').asynchImageLoader();
* });
* or
* $(function(){
* $('img.lazy').jail();
* });
* You can also have different configurations:
*
* - timeout : number of msec after that the images will be loaded - Default: 10ms
* - effect : any jQuery effect that makes the images display (e.g. "fadeIn"). If you are loading a large number of images, it is best to NOT use this setting. Effect calls are very expensive - Default: NULL
* - speed : string or number determining how long the animation will run - Default: 400
* - selector : selector that you need to bind the trigger event - Default: NULL
* - event : event that triggers the image to load. You can choose "load", "load+scroll", "click", "mouseover", or "scroll". Default: "load+scroll"
* - offset : an offset of "500" would cause any images that are less than 500px below the bottom of the window or 500px above the top of the window to load. - Default: 0
* - callback : function that will be called after the images are loaded - Default: ""
* - placeholder: location of an image (such a loader) you want to display while waiting for the images to be loaded - Default: ""
*
*
* Tested with jQuery 1.3.2+ on FF 2/3, Opera 10+, Safari 4+, Chrome on Mac and IE 6/7/8 on Win.
*
* Contributor : Derek Lindahl - dlindahl
*
* @link http://github.com/sebarmeli/JAIL
* @author Sebastiano Armeli-Battana
* @date 08/04/2011
* @version 0.8.1
*
*/
/*globals window,jQuery,setTimeout,clearTimeout */
(function($){
var $window = $(window);
$.fn.asynchImageLoader = $.fn.jail = function(options) {
// Configuration
options = $.extend({
timeout : 10,
effect : false,
speed : 400,
selector: null,
offset : 0,
event : 'load+scroll',
callback : jQuery.noop,
placeholder : false
}, options);
var images = this;
// Store the selector into 'triggerEl' data for the images selected
this.data('triggerEl', (options.selector) ? $(options.selector) : $window);
// Use a placeholder in case it is specified
if (options.placeholder !== false) {
images.each(function(){
$(this).attr("src", options.placeholder);
});
}
// When the event is not specified the images will be loaded with a delay
if(/^load/.test(options.event)) {
$.asynchImageLoader.later.call(this, options);
} else {
$.asynchImageLoader.onEvent.call(this, options, images);
}
return this;
};
// Methods cointaing the logic
$.asynchImageLoader = {
// Remove any elements that have been loaded from the jQuery stack.
// This should speed up subsequent calls by not having to iterate over the loaded elements.
_purgeStack : function(stack) {
var i = 0;
while(true) {
if(i === stack.length) {
break;
} else {
if(stack[i].getAttribute('data-href')) {
i++;
} else {
stack.splice(i, 1);
}
}
}
},
// Load the image - after the event is triggered on the image itself - no need
// to check for visibility
_loadOnEvent : function(e) {
var $img = $(this),
options = e.data.options,
images = e.data.images;
// Load images
$.asynchImageLoader._loadImage(options, $img);
// Image has been loaded so there is no need to listen anymore
$img.unbind( options.event, $.asynchImageLoader._loadOnEvent );
//Callback call
options.callback.call(this, options);
$.asynchImageLoader._purgeStack( images );
},
// Load the image - after the event is triggered by a DOM element different
// from the images (options.selector value) or the event is "scroll" -
// visibility of the images is checked
_bufferedEventListener : function(e) {
var images = e.data.images,
options = e.data.options,
triggerEl = images.data('triggerEl');
clearTimeout(images.data('poller'));
images.data('poller', setTimeout(function() {
images.each(function _imageLoader(){
$.asynchImageLoader._loadImageIfVisible(options, this, triggerEl);
});
$.asynchImageLoader._purgeStack( images );
options.callback.call(this, options, images);
}, options.timeout));
return false;
},
// Images loaded triggered by en event (event different from "load" or "load+scroll")
onEvent : function(options, images) {
images = images || this;
if (options.event === 'scroll' || options.selector) {
var triggerEl = images.data('triggerEl');
if(images.length > 0) {
// Bind the event to the selector specified in the config obj
triggerEl.bind( options.event, { images:images, options:options }, $.asynchImageLoader._bufferedEventListener );
if (options.event === 'scroll' || !options.selector) {
$window.resize({ images:images, options:options }, $.asynchImageLoader._bufferedEventListener );
}
} else {
// Unbind the event to the selector specified in the config obj since there is nothing left to do
var initalTriggerEl = (options.selector) ? $(options.selector) : $window;
initalTriggerEl.unbind( options.event, $.asynchImageLoader._bufferedEventListener );
}
} else {
// Bind the event to the images
images.bind(options.event, { options:options, images:images }, $.asynchImageLoader._loadOnEvent);
}
},
// Method called when event : "load" or "load+scroll" (default)
later : function(options) {
var images = this;
// If the 'load' event is specified, immediately load all the visible images and remove them from the stack
if (options.event === 'load') {
images.each(function(){
$.asynchImageLoader._loadImageIfVisible(options, this, images.data('triggerEl'));
});
}
$.asynchImageLoader._purgeStack( images );
// After [timeout] has elapsed, load the remaining images if they are visible OR (if no event is specified)
setTimeout(function() {
if (options.event === 'load') {
images.each(function(){
$.asynchImageLoader._loadImage(options, $(this));
});
} else {
// Method : "load+scroll"
images.each(function(){
$.asynchImageLoader._loadImageIfVisible(options, this, images.data('triggerEl'));
});
}
$.asynchImageLoader._purgeStack( images );
if (options.event === 'load+scroll') {
options.event = 'scroll';
$.asynchImageLoader.onEvent( options, images );
}
}, options.timeout);
},
// Function that checks if the images have been loaded
_loadImageIfVisible : function(options, image, triggerEl) {
var $img = $(image),
container = (options.event === 'scroll' ? triggerEl : $window);
if ($.asynchImageLoader._isInTheScreen (container, $img, options.offset)) {
$.asynchImageLoader._loadImage(options, $img);
}
},
// Function that returns true if the image is visible inside the "window" (or specified container element)
_isInTheScreen : function($ct, $img, optionOffset) {
var is_ct_window = $ct[0] === window,
ct_offset = $ct.offset() || { top:0, left:0 },
ct_top = ct_offset.top + ( is_ct_window ? $ct.scrollTop() : 0),
ct_left = ct_offset.left + ( is_ct_window ? $ct.scrollLeft() : 0),
ct_right = ct_left + $ct.width(),
ct_bottom = ct_top + $ct.height(),
img_offset = $img.offset(),
img_width = $img.width(),
img_height = $img.height();
return (ct_top - optionOffset) <= (img_offset.top + img_height) &&
(ct_bottom + optionOffset) >= img_offset.top &&
(ct_left - optionOffset)<= (img_offset.left + img_width) &&
(ct_right + optionOffset) >= img_offset.left;
},
// Main function --> Load the images copying the "data-href" attribute into the "src" attribute
_loadImage : function(options, $img) {
$img.hide();
$img.attr("src", $img.attr("data-href"));
$img.removeAttr('data-href');
// Images loaded with some effect if existing
if(options.effect) {
if (options.speed) {
$img[options.effect](options.speed);
} else {
$img[options.effect]();
}
} else {
$img.show();
}
}
};
}(jQuery));
*
* You can define a noscript block in order to respect the principles of progressive
* enhancemnt
* E.g.
*
*
* You can call the function in this way
* E.g.
* $(function(){
* $('img.lazy').asynchImageLoader();
* });
* or
* $(function(){
* $('img.lazy').jail();
* });
* You can also have different configurations:
*
* - timeout : number of msec after that the images will be loaded - Default: 10ms
* - effect : any jQuery effect that makes the images display (e.g. "fadeIn"). If you are loading a large number of images, it is best to NOT use this setting. Effect calls are very expensive - Default: NULL
* - speed : string or number determining how long the animation will run - Default: 400
* - selector : selector that you need to bind the trigger event - Default: NULL
* - event : event that triggers the image to load. You can choose "load", "load+scroll", "click", "mouseover", or "scroll". Default: "load+scroll"
* - offset : an offset of "500" would cause any images that are less than 500px below the bottom of the window or 500px above the top of the window to load. - Default: 0
* - callback : function that will be called after the images are loaded - Default: ""
* - placeholder: location of an image (such a loader) you want to display while waiting for the images to be loaded - Default: ""
*
*
* Tested with jQuery 1.3.2+ on FF 2/3, Opera 10+, Safari 4+, Chrome on Mac and IE 6/7/8 on Win.
*
* Contributor : Derek Lindahl - dlindahl
*
* @link http://github.com/sebarmeli/JAIL
* @author Sebastiano Armeli-Battana
* @date 08/04/2011
* @version 0.8.1
*
*/
/*globals window,jQuery,setTimeout,clearTimeout */
(function($){
var $window = $(window);
$.fn.asynchImageLoader = $.fn.jail = function(options) {
// Configuration
options = $.extend({
timeout : 10,
effect : false,
speed : 400,
selector: null,
offset : 0,
event : 'load+scroll',
callback : jQuery.noop,
placeholder : false
}, options);
var images = this;
// Store the selector into 'triggerEl' data for the images selected
this.data('triggerEl', (options.selector) ? $(options.selector) : $window);
// Use a placeholder in case it is specified
if (options.placeholder !== false) {
images.each(function(){
$(this).attr("src", options.placeholder);
});
}
// When the event is not specified the images will be loaded with a delay
if(/^load/.test(options.event)) {
$.asynchImageLoader.later.call(this, options);
} else {
$.asynchImageLoader.onEvent.call(this, options, images);
}
return this;
};
// Methods cointaing the logic
$.asynchImageLoader = {
// Remove any elements that have been loaded from the jQuery stack.
// This should speed up subsequent calls by not having to iterate over the loaded elements.
_purgeStack : function(stack) {
var i = 0;
while(true) {
if(i === stack.length) {
break;
} else {
if(stack[i].getAttribute('data-href')) {
i++;
} else {
stack.splice(i, 1);
}
}
}
},
// Load the image - after the event is triggered on the image itself - no need
// to check for visibility
_loadOnEvent : function(e) {
var $img = $(this),
options = e.data.options,
images = e.data.images;
// Load images
$.asynchImageLoader._loadImage(options, $img);
// Image has been loaded so there is no need to listen anymore
$img.unbind( options.event, $.asynchImageLoader._loadOnEvent );
//Callback call
options.callback.call(this, options);
$.asynchImageLoader._purgeStack( images );
},
// Load the image - after the event is triggered by a DOM element different
// from the images (options.selector value) or the event is "scroll" -
// visibility of the images is checked
_bufferedEventListener : function(e) {
var images = e.data.images,
options = e.data.options,
triggerEl = images.data('triggerEl');
clearTimeout(images.data('poller'));
images.data('poller', setTimeout(function() {
images.each(function _imageLoader(){
$.asynchImageLoader._loadImageIfVisible(options, this, triggerEl);
});
$.asynchImageLoader._purgeStack( images );
options.callback.call(this, options, images);
}, options.timeout));
return false;
},
// Images loaded triggered by en event (event different from "load" or "load+scroll")
onEvent : function(options, images) {
images = images || this;
if (options.event === 'scroll' || options.selector) {
var triggerEl = images.data('triggerEl');
if(images.length > 0) {
// Bind the event to the selector specified in the config obj
triggerEl.bind( options.event, { images:images, options:options }, $.asynchImageLoader._bufferedEventListener );
if (options.event === 'scroll' || !options.selector) {
$window.resize({ images:images, options:options }, $.asynchImageLoader._bufferedEventListener );
}
} else {
// Unbind the event to the selector specified in the config obj since there is nothing left to do
var initalTriggerEl = (options.selector) ? $(options.selector) : $window;
initalTriggerEl.unbind( options.event, $.asynchImageLoader._bufferedEventListener );
}
} else {
// Bind the event to the images
images.bind(options.event, { options:options, images:images }, $.asynchImageLoader._loadOnEvent);
}
},
// Method called when event : "load" or "load+scroll" (default)
later : function(options) {
var images = this;
// If the 'load' event is specified, immediately load all the visible images and remove them from the stack
if (options.event === 'load') {
images.each(function(){
$.asynchImageLoader._loadImageIfVisible(options, this, images.data('triggerEl'));
});
}
$.asynchImageLoader._purgeStack( images );
// After [timeout] has elapsed, load the remaining images if they are visible OR (if no event is specified)
setTimeout(function() {
if (options.event === 'load') {
images.each(function(){
$.asynchImageLoader._loadImage(options, $(this));
});
} else {
// Method : "load+scroll"
images.each(function(){
$.asynchImageLoader._loadImageIfVisible(options, this, images.data('triggerEl'));
});
}
$.asynchImageLoader._purgeStack( images );
if (options.event === 'load+scroll') {
options.event = 'scroll';
$.asynchImageLoader.onEvent( options, images );
}
}, options.timeout);
},
// Function that checks if the images have been loaded
_loadImageIfVisible : function(options, image, triggerEl) {
var $img = $(image),
container = (options.event === 'scroll' ? triggerEl : $window);
if ($.asynchImageLoader._isInTheScreen (container, $img, options.offset)) {
$.asynchImageLoader._loadImage(options, $img);
}
},
// Function that returns true if the image is visible inside the "window" (or specified container element)
_isInTheScreen : function($ct, $img, optionOffset) {
var is_ct_window = $ct[0] === window,
ct_offset = $ct.offset() || { top:0, left:0 },
ct_top = ct_offset.top + ( is_ct_window ? $ct.scrollTop() : 0),
ct_left = ct_offset.left + ( is_ct_window ? $ct.scrollLeft() : 0),
ct_right = ct_left + $ct.width(),
ct_bottom = ct_top + $ct.height(),
img_offset = $img.offset(),
img_width = $img.width(),
img_height = $img.height();
return (ct_top - optionOffset) <= (img_offset.top + img_height) &&
(ct_bottom + optionOffset) >= img_offset.top &&
(ct_left - optionOffset)<= (img_offset.left + img_width) &&
(ct_right + optionOffset) >= img_offset.left;
},
// Main function --> Load the images copying the "data-href" attribute into the "src" attribute
_loadImage : function(options, $img) {
$img.hide();
$img.attr("src", $img.attr("data-href"));
$img.removeAttr('data-href');
// Images loaded with some effect if existing
if(options.effect) {
if (options.speed) {
$img[options.effect](options.speed);
} else {
$img[options.effect]();
}
} else {
$img.show();
}
}
};
}(jQuery));