public async virtual Task <MemoryImage> LoadThumbnailImageAsync(HttpClient http, CancellationToken cancellationToken)
{
MemoryImage?image = null;
try
{
using var response = await http.GetAsync(this.ThumbnailImageUrl, cancellationToken)
.ConfigureAwait(false);
response.EnsureSuccessStatusCode();
using var imageStream = await response.Content.ReadAsStreamAsync()
.ConfigureAwait(false);
image = await MemoryImage.CopyFromStreamAsync(imageStream)
.ConfigureAwait(false);
cancellationToken.ThrowIfCancellationRequested();
return(image);
}
catch (OperationCanceledException)
{
image?.Dispose();
throw;
}
}
/// <summary>
/// Release all resources used by this <see cref="DoubleBufferedGraphics"/>.
/// </summary>
public void Dispose()
{
if (MemoryImage != null)
{
MemoryImage.Dispose();
MemoryImage = null;
}
if (Graphics != null)
{
Graphics.Dispose();
Graphics = null;
}
}
/// <summary>指定されたタイル番号のタイル画像を読み込むメソッド</summary>
private async Task <MemoryImage> LoadTileImageAsync(HttpClient http, Point pos)
{
var tileUrl = TileServerBase + $"/{this.Zoom}/{pos.X}/{pos.Y}.png";
using (var stream = await http.GetStreamAsync(tileUrl).ConfigureAwait(false))
{
MemoryImage result = null;
try
{
result = await MemoryImage.CopyFromStreamAsync(stream).ConfigureAwait(false);
return(result);
}
catch { result?.Dispose(); throw; }
}
}
/// <summary>
/// Reset this <see cref="DoubleBufferedGraphics"/>.
/// </summary>
public void Reset()
{
if (MemoryImage != null)
{
MemoryImage.Dispose();
MemoryImage = null;
}
if (Graphics != null)
{
Graphics.Dispose();
Graphics = null;
}
MemoryImage = new Bitmap(Size.Width, Size.Height);
Graphics = Graphics.FromImage(MemoryImage);
}
/// <summary>
/// This method is the preferred method of drawing a background image.
/// It is *MUCH* faster than any of the Graphics.DrawImage() methods.
/// Warning: The memory image and the <see cref="System.Drawing.Graphics"/> object
/// will be reset after calling this method. This should be your first
/// drawing operation.
/// </summary>
/// <param name="image">The image to draw.</param>
public void SetBackgroundImage(Image image)
{
if (MemoryImage != null)
{
MemoryImage.Dispose();
MemoryImage = null;
}
if (Graphics != null)
{
Graphics.Dispose();
Graphics = null;
}
MemoryImage = image.Clone() as Image;
if (MemoryImage != null)
{
Graphics = Graphics.FromImage(MemoryImage);
}
}
public override async Task <MemoryImage> LoadThumbnailImageAsync(HttpClient http, CancellationToken cancellationToken)
{
// 画像中央に描画されるタイル (ピクセル単位ではなくタイル番号を表す)
// タイル番号に小数部が含まれているが、これはタイル内の相対的な位置を表すためこのまま保持する
var centerTileNum = this.WorldToTilePos(this.Longitude, this.Latitude, this.Zoom);
// 画像左上に描画されるタイル
var topLeftTileNum = PointF.Add(centerTileNum, new SizeF(-this.ThumbnailSize.Width / 2.0f / TileSize.Width, -this.ThumbnailSize.Height / 2.0f / TileSize.Height));
// タイル番号の小数部をもとに、タイル画像を描画する際のピクセル単位のオフセットを算出する
var tileOffset = Size.Round(new SizeF(-TileSize.Width * (topLeftTileNum.X - (int)topLeftTileNum.X), -TileSize.Height * (topLeftTileNum.Y - (int)topLeftTileNum.Y)));
// 縦横のタイル枚数
var tileCountX = (int)Math.Ceiling((double)(this.ThumbnailSize.Width + Math.Abs(tileOffset.Width)) / TileSize.Width);
var tileCountY = (int)Math.Ceiling((double)(this.ThumbnailSize.Height + Math.Abs(tileOffset.Height)) / TileSize.Height);
// 読み込む対象となるタイル画像が 10 枚を越えていたら中断
// ex. 一辺が 512px 以内のサムネイル画像を生成する場合、必要なタイル画像は最大で 9 枚
if (tileCountX * tileCountY > 10)
{
throw new OperationCanceledException();
}
// タイル画像を読み込む
var tilesTask = new Task <MemoryImage> [tileCountX, tileCountY];
foreach (var x in Enumerable.Range(0, tileCountX))
{
foreach (var y in Enumerable.Range(0, tileCountY))
{
var tilePos = Point.Add(Point.Truncate(topLeftTileNum), new Size(x, y));
tilesTask[x, y] = this.LoadTileImageAsync(http, tilePos);
}
}
await Task.WhenAll(tilesTask.Cast <Task <MemoryImage> >())
.ConfigureAwait(false);
using (var bitmap = new Bitmap(this.ThumbnailSize.Width, this.ThumbnailSize.Height))
{
using (var g = Graphics.FromImage(bitmap))
{
g.TranslateTransform(tileOffset.Width, tileOffset.Height);
foreach (var x in Enumerable.Range(0, tileCountX))
{
foreach (var y in Enumerable.Range(0, tileCountY))
{
using (var image = tilesTask[x, y].Result)
{
g.DrawImage(image.Image, TileSize.Width * x, TileSize.Height * y);
}
}
}
}
MemoryImage result = null;
try
{
result = MemoryImage.CopyFromImage(bitmap);
return(result);
}
catch { result?.Dispose(); throw; }
}
}