PHP：创建文件并保留文件权限(PHP: Creating files and preserving file permissions)

 这里有一个javascript脚本，可以完全满足您的需求 
 
 Retina.js 
 
 无需重新发明轮子:) 
 
 它检查高DPI显示如下： 
 
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;
    };
 
 并使用以下内容添加后缀（默认为@ 2x） 
 
var regexMatch = /\.[\w\?=]+$/;
function suffixReplace (match) {
        return config.retinaImageSuffix + match;
    }

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 {
            if (undefined !== document.createElement) {
                var locationObject = document.createElement('a');
                locationObject.href = this.path;
                locationObject.pathname = locationObject.pathname.replace(regexMatch, suffixReplace);
                this.at_2x_path = locationObject.href;
            } else {
                var parts = this.path.split('?');
                parts[0] = parts[0].replace(regexMatch, suffixReplace);
                this.at_2x_path = parts.join('?');
            }
            this.perform_check = true;
        }
    }

There's a javascript script for this that does exactly what you need
 
Retina.js
 
No need to reinvent the wheel :) 
 
It checks for high DPI displays as follows:
 
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;
    };
 
And uses the following to add the suffix, (by default @2x)
 
var regexMatch = /\.[\w\?=]+$/;
function suffixReplace (match) {
        return config.retinaImageSuffix + match;
    }

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 {
            if (undefined !== document.createElement) {
                var locationObject = document.createElement('a');
                locationObject.href = this.path;
                locationObject.pathname = locationObject.pathname.replace(regexMatch, suffixReplace);
                this.at_2x_path = locationObject.href;
            } else {
                var parts = this.path.split('?');
                parts[0] = parts[0].replace(regexMatch, suffixReplace);
                this.at_2x_path = parts.join('?');
            }
            this.perform_check = true;
        }
    }