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Imager.js (as of 14th August 2013)
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| (function (window, document) { | |
| 'use strict'; | |
| var $, Imager; | |
| window.requestAnimationFrame = | |
| window.requestAnimationFrame || | |
| window.mozRequestAnimationFrame || | |
| window.webkitRequestAnimationFrame || | |
| function (callback) { | |
| window.setTimeout(callback, 1000 / 60); | |
| }; | |
| $ = (function (dollar) { | |
| if (dollar) { | |
| return dollar; | |
| } | |
| return function (selector) { | |
| return Array.prototype.slice.call(document.querySelectorAll(selector)); | |
| }; | |
| }(window.$)); | |
| /* | |
| Construct a new Imager instance, passing an optional configuration object. | |
| Example usage: | |
| { | |
| // Available widths for your images | |
| availableWidths: [Number] | |
| // Selector to be used to locate your div placeholders | |
| selector: '', | |
| // Class name to give your resizable images. | |
| className: '', | |
| // Regular expression to match against your image endpoint's naming conventions | |
| // e.g. http://yourserver.com/image/horse/400 | |
| regex: RegExp | |
| } | |
| @param {object} configuration settings | |
| @return {object} instance of Imager | |
| */ | |
| window.Imager = Imager = function (opts) { | |
| var self = this; | |
| opts = opts || {}; | |
| this.availableWidths = opts.availableWidths || [96, 130, 165, 200, 235, 270, 304, 340, 375, 410, 445, 485, 520, 555, 590, 625, 660, 695, 736]; | |
| this.selector = opts.selector || '.delayed-image-load'; | |
| this.className = '.' + (opts.className || 'image-replace').replace(/^\.+/, '.'); | |
| this.regex = opts.regex || /^(.+\/)\d+$/i; | |
| this.gif = document.createElement('img'); | |
| this.gif.src = 'data:image/gif;base64,R0lGODlhEAAJAIAAAP///wAAACH5BAEAAAAALAAAAAAQAAkAAAIKhI+py+0Po5yUFQA7'; | |
| this.gif.className = this.className.replace(/^[#.]/, ''); | |
| this.divs = $(this.selector); | |
| this.cache = {}; | |
| this.changeDivsToEmptyImages(); | |
| window.requestAnimationFrame(function(){ | |
| self.init(); | |
| }); | |
| }; | |
| Imager.prototype.init = function () { | |
| var self = this; | |
| this.initialized = true; | |
| this.checkImagesNeedReplacing(); | |
| window.addEventListener('resize', function(){ | |
| self.checkImagesNeedReplacing(); | |
| }, false); | |
| }; | |
| Imager.prototype.changeDivsToEmptyImages = function () { | |
| var divs = this.divs, | |
| i = divs.length, | |
| gif; | |
| while (i--) { | |
| gif = this.gif.cloneNode(false); | |
| gif.width = divs[i].getAttribute('data-width'); | |
| gif.setAttribute('data-src', divs[i].getAttribute('data-src')); | |
| divs[i].parentNode.replaceChild(gif, divs[i]); | |
| } | |
| if (this.initialized) { | |
| this.checkImagesNeedReplacing(); | |
| } | |
| }; | |
| Imager.prototype.checkImagesNeedReplacing = function () { | |
| var self = this, | |
| images = $(this.className), | |
| i = images.length; | |
| if (!this.isResizing) { | |
| this.isResizing = true; | |
| while (i--) { | |
| this.replaceImagesBasedOnScreenDimensions(images[i]); | |
| } | |
| this.isResizing = false; | |
| } | |
| }; | |
| Imager.prototype.replaceImagesBasedOnScreenDimensions = function (image) { | |
| var src = this.determineAppropriateResolution(image), | |
| parent = image.parentNode, | |
| replacedImage; | |
| if (this.cache[src]) { | |
| replacedImage = this.cache[src].cloneNode(false); | |
| replacedImage.width = image.getAttribute('width'); | |
| } else { | |
| replacedImage = image.cloneNode(false); | |
| replacedImage.src = src; | |
| this.cache[src] = replacedImage; | |
| } | |
| parent.replaceChild(replacedImage, image); | |
| }; | |
| Imager.prototype.determineAppropriateResolution = function (image) { | |
| var src = image.getAttribute('data-src'), | |
| imagewidth = image.clientWidth, | |
| selectedWidth = this.availableWidths[0], | |
| i = this.availableWidths.length; | |
| while (i--) { | |
| if (imagewidth <= this.availableWidths[i]) { | |
| selectedWidth = this.availableWidths[i]; | |
| } | |
| } | |
| return this.changeImageSrcToUseNewImageDimensions(src, selectedWidth); | |
| }; | |
| Imager.prototype.changeImageSrcToUseNewImageDimensions = function (src, selectedWidth) { | |
| return src.replace(this.regex, function (match, captured) { | |
| return captured + selectedWidth; | |
| }); | |
| }; | |
| }(window, document)); |
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