Access denied while saving image in UWP.Access is

I am working on universal windows app on Windows 10 SDK to draw rectangle on faces recognized in the image.

I am using Win2D to edit the pictures and draw rectangle on it. I am able to read files from the Pictures library but when I try to save the image after editing it gives the following error:

Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))

The following is the method I used to draw rectangle on the image:

private async void DrawRect()
    {
        CanvasDevice device = CanvasDevice.GetSharedDevice();
        CanvasBitmap bitmap = null;
        CanvasRenderTarget offscreen = null;

        Windows.Storage.StorageFile photofile = await KnownFolders.PicturesLibrary.GetFileAsync("image.jpg");

        if(photofile != null)
        {
            using (var stream = await photofile.OpenReadAsync())
            {
                bitmap = await CanvasBitmap.LoadAsync(device, stream);
            }
        }

        if(bitmap != null)
        {
            offscreen = new CanvasRenderTarget(device, bitmap.SizeInPixels.Width, bitmap.SizeInPixels.Height, 96);
            using (var ds = offscreen.CreateDrawingSession())
            {
                ds.Clear(Colors.Transparent);
                ds.DrawImage(bitmap);
                ds.DrawRectangle(25, 35, 270, 352, Colors.Blue,4);
            }

            var photoFile = await KnownFolders.PicturesLibrary.CreateFileAsync("image2.jpg", CreationCollisionOption.ReplaceExisting);                        

            if (photofile != null)
            {
                await offscreen.SaveAsync(photofile.Path);
            }              

            //await offscreen.SaveAsync(photoFile.Path);*/
        }
    }

The exception is thrown at the last line offscreen.SaveAsync.

The stack trace for the above error is:

at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Runtime.CompilerServices.TaskAwaiter.GetResult() at IdentifyFacesApp.IdentifiedFaces.d__5.MoveNext()

I have set the permissions for accessing the pictures folders in the appmanifest file.

Do I need to set some additional permissions to save the image in the disk.

The same error occurs when I tried to save the image in any other location.

Try to access the file by the stream, not the path:

var photoFile = await KnownFolders.PicturesLibrary.CreateFileAsync("image2.jpg", CreationCollisionOption.ReplaceExisting);

if (photofile != null)
{
    using (var stream = await photofile.OpenAsync(FileAccessMode.ReadWrite))
    {
        await offscreen.SaveAsync(stream, CanvasBitmapFileFormat.Jpeg);
    }
}

In UWP if you access files via path, you will likely get Access Denied in many cases, it should be done via StorageFile.