/// <summary>
/// Decode and resize <paramref name="encodedData"/> so that it fits in
/// <paramref name="thumbnailAreaSize"/> but preserves its aspect ratio.
/// </summary>
/// <param name="encodedData">Encoded image data</param>
/// <param name="thumbnailAreaSize">Size of the area for thumbnail</param>
/// <param name="entity">Image metadata</param>
/// <param name="save">If true, the generated thumbnail will be cached</param>
/// <returns>Processed thumbnail image</returns>
private Thumbnail Process(byte[] encodedData, Size thumbnailAreaSize, IEntity entity, bool save)
{
using (var input = new MemoryStream(encodedData))
{
// read image metadata
var info = new ImageFileInfo(input);
Size original = Size.Empty;
if (info.Frames.Length > 0)
{
original.Width = info.Frames[0].Width;
original.Height = info.Frames[0].Height;
}
input.Position = 0;
// create thumbnail image
var decoded = _imageLoader.Decode(entity, input, thumbnailAreaSize);
// save processed thumbnail
if (save)
{
SaveThumbnail(entity, decoded);
}
// Create thumbnail wrapper
return(new Thumbnail(
Image.FromStream(new MemoryStream(decoded), false), original));
}
}
/// <summary>
/// Add a new load request to the queue
/// </summary>
/// <param name="entity">Entity to load</param>
/// <returns>
/// Task finished when <paramref name="entity"/> is loaded or the loading failed.
/// </returns>
public Task <SKBitmap> EnqueueAsync(IEntity entity)
{
if (entity == null)
{
throw new ArgumentNullException(nameof(entity));
}
var version = _queueVersion;
var promise = new TaskCompletionSource <SKBitmap>();
_queue = _queue.ContinueWith(_ =>
{
// check if this request has been cancelled
if (version != _queueVersion)
{
promise.SetResult(null);
return;
}
try
{
var image = SKBitmap.Decode(_imageLoader.Decode(entity));
// if the request has been canceled, dispose the image
if (version != _queueVersion)
{
image?.Dispose();
image = null;
}
promise.SetResult(image);
}
catch (OperationCanceledException)
{
promise.SetCanceled();
}
catch (Exception e)
{
promise.SetException(e);
}
});
return(promise.Task);
}
