使用WinRT编辑图片文件的基本和高级属性

这里所谓的基本属性是指：tags (keywords), rating。高级属性是指：geographic information (including latitude and longitude) 。      Step1: 打开File Picker选择图片文件：                 var picker = new Windows.Storage.Pickers.FileOpenPick();                picker.viewMode = Windows.Storage.Pickers.PickerViewMode.thumbnail;                picker.pickSingleFileAsync().then(function (file) {... ...});        Step2: 使用得到的file object得到image properties object:                 file.properties.getImagePropertiesAsync().then(function (imageProperties) {... ...});        Step3: 使用得到的image properites object获取图片文件的基本属性：                 imageProperites.title = tileValue;                imageProperties.rating = userRating;        // rating的范围是0~99                imageProperites.keywords.append(keyword);    // keywords可以添加多个，系统会自动用“;"分割，无需用户添加        Step4: 获取图片文件高级属性对象advProperites, 并使用它访问geographic information:                 imageProperites.retrievePropertiesAsync(                      ["System.GPS .LatitudeNumerator",                        "System.GPS.LatitudeDenominator",                        "System.GPS.LongitudeNumerator",                       "System.GPS.LongitudeDenominator"]                ).then(function(advProperties) {                      advProperties.insert("System.GPS.LatitudeNumerator", latNum);                        advProperties.insert("System.GPS.LatitudeDenominator", latDen);                       advProperties.insert("System.GPS.LongitudeNumerator", longNum);                       advProperties.insert("System.GPS.LongitudeDenominator", longDen);                });      特别注意，rating这个属性必须要大于0，否则keywords以及geographic information均无法修改和访问。