C# Layer.Draw方法代碼示例

		public void Start (BaseEffect effect)
		{			
			if (live_preview_enabled)
				throw new InvalidOperationException ("LivePreviewManager.Start() called while live preview is already enabled.");
			
			// Create live preview surface.
			// Start rendering.
			// Listen for changes to effectConfiguration object, and restart render if needed.

			live_preview_enabled = true;
			apply_live_preview_flag = false;
			cancel_live_preview_flag = false;
			
			layer = PintaCore.Layers.CurrentLayer;
			this.effect = effect;

			//TODO Use the current tool layer instead.
			live_preview_surface = new Cairo.ImageSurface (Cairo.Format.Argb32,
			                                  PintaCore.Workspace.ImageSize.Width,
			                                  PintaCore.Workspace.ImageSize.Height);

			// Handle selection path.
			PintaCore.Tools.Commit ();
			selection_path = (PintaCore.Layers.ShowSelection) ? PintaCore.Workspace.ActiveDocument.Selection.SelectionPath : null;
			render_bounds = (selection_path != null) ? selection_path.GetBounds () : live_preview_surface.GetBounds ();
			render_bounds = PintaCore.Workspace.ClampToImageSize (render_bounds);	

			history_item = new SimpleHistoryItem (effect.Icon, effect.Name);
			history_item.TakeSnapshotOfLayer (PintaCore.Layers.CurrentLayerIndex);	
			
			// Paint the pre-effect layer surface into into the working surface.
			using (var ctx = new Cairo.Context (live_preview_surface)) {
				layer.Draw(ctx, layer.Surface, 1);
			}
			
			if (effect.EffectData != null)
				effect.EffectData.PropertyChanged += EffectData_PropertyChanged;
			
			if (Started != null) {
				Started (this, new LivePreviewStartedEventArgs());
			}
			
			var settings = new AsyncEffectRenderer.Settings () {
				ThreadCount = PintaCore.System.RenderThreads,
				TileWidth = render_bounds.Width,
				TileHeight = 1,
				ThreadPriority = ThreadPriority.BelowNormal
			};
			
			Debug.WriteLine (DateTime.Now.ToString("HH:mm:ss:ffff") + "Start Live preview.");
			
			renderer = new Renderer (this, settings);
			renderer.Start (effect, layer.Surface, live_preview_surface, render_bounds);
			
			if (effect.IsConfigurable) {		
				if (!effect.LaunchConfiguration ()) {
					PintaCore.Chrome.MainWindowBusy = true;
					Cancel ();
				} else {
					PintaCore.Chrome.MainWindowBusy = true;
					Apply ();
				}
			} else {
				PintaCore.Chrome.MainWindowBusy = true;
				Apply ();
			}
		}

        private Layer CreateOffsetLayer(Layer original)
        {
            var offset = OffsetLayer;
            offset.Surface.Clear ();

            using (var g = new Cairo.Context (offset.Surface)) {
                original.Draw(g, original.Surface, 1);
            }

            offset.BlendMode = original.BlendMode;
            offset.Transform.InitMatrix(original.Transform);
            offset.Opacity = original.Opacity;

            return offset;
        }