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orbit-4-1/app/assets/javascripts/lib/retina.js

144 lines
3.7 KiB
JavaScript

(function() {
var root = (typeof exports == 'undefined' ? window : exports);
var config = {
// Ensure Content-Type is an image before trying to load @2x image
// https://github.com/imulus/retinajs/pull/45)
check_mime_type: true
};
root.Retina = Retina;
function Retina() {}
Retina.configure = function(options) {
if (options == null) options = {};
for (var prop in options) config[prop] = options[prop];
};
Retina.init = function(context) {
if (context == null) context = root;
var existing_onload = context.onload || new Function;
context.onload = function() {
var images = document.getElementsByTagName("img"), retinaImages = [], i, image;
for (i = 0; i < images.length; i++) {
image = images[i];
retinaImages.push(new RetinaImage(image));
}
existing_onload();
}
};
Retina.isRetina = function(){
var mediaQuery = "(-webkit-min-device-pixel-ratio: 1.5),\
(min--moz-device-pixel-ratio: 1.5),\
(-o-min-device-pixel-ratio: 3/2),\
(min-resolution: 1.5dppx)";
if (root.devicePixelRatio > 1)
return true;
if (root.matchMedia && root.matchMedia(mediaQuery).matches)
return true;
return false;
};
root.RetinaImagePath = RetinaImagePath;
function RetinaImagePath(path, at_2x_path) {
this.path = path;
if (typeof at_2x_path !== "undefined" && at_2x_path !== null) {
this.at_2x_path = at_2x_path;
this.perform_check = false;
} else {
this.at_2x_path = path.replace(/\.\w+$/, function(match) { return "@2x" + match; });
this.perform_check = true;
}
}
RetinaImagePath.confirmed_paths = [];
RetinaImagePath.prototype.is_external = function() {
return !!(this.path.match(/^https?\:/i) && !this.path.match('//' + document.domain) )
}
RetinaImagePath.prototype.check_2x_variant = function(callback) {
var http, that = this;
if (this.is_external()) {
return callback(false);
} else if (!this.perform_check && typeof this.at_2x_path !== "undefined" && this.at_2x_path !== null) {
return callback(true);
} else if (this.at_2x_path in RetinaImagePath.confirmed_paths) {
return callback(true);
} else {
http = new XMLHttpRequest;
http.open('HEAD', this.at_2x_path);
http.onreadystatechange = function() {
if (http.readyState != 4) {
return callback(false);
}
if (http.status >= 200 && http.status <= 399) {
if (config.check_mime_type) {
var type = http.getResponseHeader('Content-Type');
if (type == null || !type.match(/^image/i)) {
return callback(false);
}
}
RetinaImagePath.confirmed_paths.push(that.at_2x_path);
return callback(true);
} else {
return callback(false);
}
}
http.send();
}
}
function RetinaImage(el) {
this.el = el;
this.path = new RetinaImagePath(this.el.getAttribute('src'), this.el.getAttribute('data-at2x'));
var that = this;
this.path.check_2x_variant(function(hasVariant) {
if (hasVariant) that.swap();
});
}
root.RetinaImage = RetinaImage;
RetinaImage.prototype.swap = function(path) {
if (typeof path == 'undefined') path = this.path.at_2x_path;
var that = this;
function load() {
if (! that.el.complete) {
setTimeout(load, 5);
} else {
that.el.setAttribute('width', that.el.offsetWidth);
that.el.setAttribute('height', that.el.offsetHeight);
that.el.setAttribute('src', path);
}
}
load();
}
if (Retina.isRetina()) {
Retina.init(root);
}
})();