winjs图片文件大小

Question

I'm trying to get the size (pixel, bites) from a picture in a Win 8 app. I pick the file with the openPicker and I get the file. But I can't find the size attributes? I'll display an error, if the file is to large. Any idea how I can get this info? Thanks.

Answer 1

After some more hours of searching and trying I've solved it like this:

//add picture
        document.getElementById("btnAddImg").addEventListener('click', function () {
            // Create the picker object and set options
            var openPicker = new Windows.Storage.Pickers.FileOpenPicker();
            openPicker.viewMode = Windows.Storage.Pickers.PickerViewMode.thumbnail;
            openPicker.suggestedStartLocation = Windows.Storage.Pickers.PickerLocationId.picturesLibrary;
            openPicker.fileTypeFilter.replaceAll([".png", ".jpg", ".jpeg"]);
             openPicker.pickSingleFileAsync().then(function (file) {
                file.openAsync(Windows.Storage.FileAccessMode.read).done(function (stream) {
                    var fileType = file.contentType;
                    var blob = MSApp.createBlobFromRandomAccessStream(fileType, stream);
                    var fdata = new FormData();
                    fdata.append('upload_field', blob);
                    //more code....
                });
             });
        });

Hope it helps some others.

Answer 2

You can get this information through the StorageFile object itself, without having to open the file or load it into memory.

For convenience, let's say myFile is the StorageFile in question.

For image dimensions, call myFile.properties.getImagePropertiesAsync , the result of this is an ImageProperties object that contains width and height properties. You can find an example of retrieving ImageProperties in the Simple imaging sample , scenario 1.

For the file size, call myFile.getBasicPropertiesAsync . The result is a BasicProperties object whose size property has that value.