Saturday, February 7, 2015

WP App part 4 - "the Manual Automatic" - Saving and Loading images from and to a byte array

Create the functionality to use images from the phone / take image with my phone for my Windows Phone App 'The Manual Automatic" 

Previous parts:

First setup in part 1:

The setup of the DataModel in part 2:

Using the FilePicker in part 3:

It has been a little while since I posted about my project of developing the Manual Automatic app for Windows Phone. But a lot of work has been done since then. So now first I will show how I managed to store images in my Json datamodel.

Part 4 - Saving and Loading images in JSON

I want the images to be stored and not just referenced if all possible. That way it isn't lost if you delete the picture from your camarea library, because you might not want to have all those pictures of pages in your library.

So it would be great if the image can be stored in json.

Step 1 - Converting the image to a byte array and saving it
I want to store the picture in a array of ytes, so in my datamodel it looks like this:

    public class Manual
        public int ID { get; set; }
        public string ManualName { get; set; }
        public string Description { get; set; }
        public DateTime Created { get; set; }
        public DateTime Changed { get; set; }
        public byte[] Image { get; set; }

I have a byte array named Image.
After selecting the image with the FilePicker (see previous part) the WriteableBitmap originalBitmap variabele and the byte[] buffer variabele are filled. I used the originalBitmap to bind it to the Image control on the XAML.

private async void OnFilesOpenPicked(IReadOnlyList<StorageFile> files)
    // Load picked file
    if (files.Count > 0)
        // Check if image and pick first file to show
        var imageFile = files.FirstOrDefault(f => SupportedImageFileTypes.Contains(f.FileType.ToLower()));
        if (imageFile != null)
            using (var stream = await imageFile.OpenReadAsync())
                originalBitmap = await new WriteableBitmap(1, 1).FromStream(stream);
                RandomAccessStreamReference rasr = RandomAccessStreamReference.CreateFromStream(stream);
                var streamWithContent = await rasr.OpenReadAsync();
                buffer = new byte[streamWithContent.Size];
                await streamWithContent.ReadAsync(buffer.AsBuffer(), (uint)streamWithContent.Size, InputStreamOptions.None);
            Image.Source = originalBitmap;



The buffer needs to be stored.
Since that allready is a byte[] I can simply store it in my DataModel.

So on the saveButton click event I do some checks and then call

App.DataModel.AddManual(manualNameTextBox.Text, manualDescriptionTextBox.Text, buffer);

There I set the buffer to the manual.Image ad call the sveManualDataAsync(); function

manual.ManualName = manualname;
manual.Description = description;
manual.Created = DateTime.Now;
manual.Changed = DateTime.Now;
manual.Image = buffer;


await saveManualDataAsync();

There the data will be save, see the previous post for more details.

Step 2 - Loading the Image and converting it back from byte[] to WritableBitmap.

From the Main page, where the user can search for records, they can click on the results and then it neds to open on a seperate page. On that page I want to show detailed record information and also the image. So there the byte{} needs to be converted back to an image.

On the Main page I use the code below to generate results;

private void genResult(DataModel.Manual manual)
            TextBlock NameText = new TextBlock();
            NameText.Text = "Manual Name: " + manual.ManualName;
            NameText.FontSize = 22;
            //Store the manual in the Tag so we can pass it along
            NameText.Tag = manual;
            NameText.TextTrimming = TextTrimming.CharacterEllipsis;        
            NameText.Tapped += new TappedEventHandler(NameClickedEvent);
            TextBlock DescText = new TextBlock();
            DescText.Text = "Description: " + manual.Description;
            DescText.FontSize = 12;
            DescText.TextWrapping = TextWrapping.WrapWholeWords;

            TextBlock CreateText = new TextBlock();
            CreateText.Text = "Created on: " + manual.Created;
            CreateText.FontSize = 12;
            TextBlock IDText = new TextBlock();
            IDText.Text = "ID: " + manual.ID;
            IDText.FontSize = 12;

            TextBlock ImageStringText = new TextBlock();
            ImageStringText.Text = "ImageString: " + manual.ImageString;
            ImageStringText.FontSize = 12;



In the NameClickedEvent I navigate to the RecordPage

private void NameClickedEvent(object sender, TappedRoutedEventArgs e)
            //Get the manual from the textblock tag and pass it along to the ReordPage
            TextBlock textBlock = sender as TextBlock;
            DataModel.Manual manual = textBlock.Tag as DataModel.Manual;

            Frame.Navigate(typeof(RecordPage), manual);

On the RecordPage in the OnNavigatedTo I do the following:

 protected async override void OnNavigatedTo(NavigationEventArgs e)
            //get the vars and get the one manual
            var manual = (DataModel.Manual)e.Parameter;
            //should not occur that the passed manual is empty but check anyway
            if (manual != null)
                ManualNameTextBlock.Text = manual.ManualName.ToString();
                CreatedTextBlock.Text = CreatedTextBlock.Text + manual.Created.ToString();
                DescriptionTextBlock.Text = manual.Description.ToString();

                if (manual.Image != null)
                    MemoryStream _stream = new MemoryStream(manual.Image);
                    ManualImage.Source = await new WriteableBitmap(1, 1).FromStream(_stream);

                //Show a blank Image if no image is returned
                if (ManualImage.Source == null)
                    ManualImage.Source = ImageFromRelativePath(this, "Assets/empty.png");  
                //show a message that searchterm is required
                string messageText = "Something went wrong, please go back and re-select a Manual";
                MessageDialog msgBox = new MessageDialog(messageText);

                await msgBox.ShowAsync();


So the byte[] is converted back to in WriteableBitmap and set to the source of the Image.

But an error occurs when I do just that:

An exception of type 'System.Exception' occurred in but was not handled in user code

Additional information: The component cannot be found. (Exception from HRESULT: 0x88982F50)

If there is a handler for this exception, the program may be safely continued

I have no idea why this happens, and after searchig online for hours I still can't get it to work.
I use the same loading image from byte[] method to show the image after picked by the file picker and no error occurs. But when first storing it in the json file and the retreiving it messes it up...

At some point it worked, but after a few mote tests it broke again... Sounds stupid, but I cannot find a way to reproduce the corect working again... Something must be off.

After testing and searching I realize that this maybe isn't the best way to store images. In one of my tests I crate maybe 10 records with images and the json files grew to 11MB. So I van only imagine how big the files becomes after a while...
This will not be the correct way I gues

So i decide to not store the images in the json file. I now want to store a copy of the images in a folder in the Localfolder of the app. 

Once that is done I will post about it in a new blog post.