C# Context.SetSourceColor方法代码示例

        static void Main()
        {
            // The using statement ensures that potentially heavy objects
            // are disposed immediately.
            using (ImageSurface draw = new ImageSurface(Format.Argb32, 70, 150))
            {
                using (Context gr = new Context(draw))
                {
                    gr.Antialias = Antialias.Subpixel;    // sets the anti-aliasing method
                    gr.LineWidth = 9;          // sets the line width
                    gr.SetSourceColor(new Color(0, 0, 0, 1));   // red, green, blue, alpha
                    gr.MoveTo(10, 10);          // sets the Context's start point.
                    gr.LineTo(40, 60);          // draws a "virtual" line from 5,5 to 20,30
                    gr.Stroke();          //stroke the line to the image surface

                    gr.Antialias = Antialias.Gray;
                    gr.LineWidth = 8;
                    gr.SetSourceColor(new Color(1, 0, 0, 1));
                    gr.LineCap = LineCap.Round;
                    gr.MoveTo(10, 50);
                    gr.LineTo(40, 100);
                    gr.Stroke();

                    gr.Antialias = Antialias.None;    //fastest method but low quality
                    gr.LineWidth = 7;
                    gr.MoveTo(10, 90);
                    gr.LineTo(40, 140);
                    gr.Stroke();

                    draw.WriteToPng("antialias.png");  //save the image as a png image.
                }
            }
        }

        private void Form1_Shown(object sender, EventArgs e)
        {
            Debug.WriteLine("Form1_Shown");

            Win32Surface = new Win32Surface(this.CreateGraphics().GetHdc());
            FontContext = new Context(Win32Surface);

            //CRITICAL: Format of Win32Surface and ImageSurface must be identical!

            ImageSurface = new ImageSurface(Format.Rgb24, ClientSize.Width, ClientSize.Height);
            BackContext = new Context(ImageSurface);

            //Clear Surface2
            BackContext.SetSourceColor(new Color(1,1,1));
            BackContext.Operator = Operator.Source;
            BackContext.Paint();
            BackContext.Operator = Operator.Over;

            var textFormat = DWriteCairo.CreateTextFormat(
                "Arial",
                FontWeight.Normal,
                FontStyle.Normal,
                FontStretch.Normal,
                32f);
            
            Debug.Assert(Math.Abs(textFormat.FontSize - 32f) < 0.0001);
            
            const string s = "Hello World";
            textLayout = DWriteCairo.CreateTextLayout(s, textFormat, 300, 40);

        }

        public override void Apply (CanvasItem item, Context cr)
        {
            int steps = ShadowSize;
            double opacity_step = ShadowOpacity / ShadowSize;
            Color color = new Color (0, 0, 0);

            double width = Math.Round (item.Allocation.Width);
            double height = Math.Round (item.Allocation.Height);

            if (Fill != null) {
                cr.Rectangle (shadow_size, shadow_size, width - ShadowSize * 2, height - ShadowSize * 2);
                Fill.Apply (cr);
                cr.Fill ();
            }

            cr.LineWidth = 1.0;

            for (int i = 0; i < steps; i++) {
                CairoExtensions.RoundedRectangle (cr,
                    i + 0.5,
                    i + 0.5,
                    (width - 2 * i) - 1,
                    (height - 2 * i) - 1,
                    steps - i);

                color.A = opacity_step * (i + 1);
		cr.SetSourceColor (color);
                cr.Stroke ();
            }
        }

 private void Image_Loaded(object sender, RoutedEventArgs e)
 {
     Image image = (Image)sender;
     using (ImageSurface surface = new ImageSurface(Format.Argb32, (int)image.Width, (int)image.Height))
     {
         using (Context context = new Context(surface))
         {
             PointD p = new PointD(10.0, 10.0);
             PointD p2 = new PointD(100.0, 10.0);
             PointD p3 = new PointD(100.0, 100.0);
             PointD p4 = new PointD(10.0, 100.0);
             context.MoveTo(p);
             context.LineTo(p2);
             context.LineTo(p3);
             context.LineTo(p4);
             context.LineTo(p);
             context.ClosePath();
             context.Fill();
             context.MoveTo(140.0, 110.0);
             context.SetFontSize(32.0);
             context.SetSourceColor(new Color(0.0, 0.0, 0.8, 1.0));
             context.ShowText("Hello Cairo!");
             surface.Flush();
             RgbaBitmapSource source = new RgbaBitmapSource(surface.Data, surface.Width);
             image.Source = source;
         }
     }
 }

        protected override void Draw(Context cr, Pixbuf prev, Pixbuf next, int width, int height, double progress)
        {
            cr.SetSourceColor (new Color (0, 0, 0, progress));
            if (next != null) {
                double scale = Math.Min ((double)width/(double)next.Width, (double)height/(double)next.Height);
                cr.Save ();

                cr.Rectangle (0, 0, width, .5 * (height - scale*next.Height));
                cr.Fill ();

                cr.Rectangle (0, height - .5 * (height - scale*next.Height), width, .5 * (height - scale*next.Height));
                cr.Fill ();

                cr.Rectangle (0, 0, .5 * (width - scale*next.Width), height);
                cr.Fill ();

                cr.Rectangle (width - .5 * (width - scale*next.Width), 0, .5 * (width - scale*next.Width), height);
                cr.Fill ();

                cr.Rectangle (0, 0, width, height);
                cr.Scale (scale, scale);
                CairoHelper.SetSourcePixbuf (cr, next, .5 * ((double)width/scale - next.Width), .5 * ((double)height/scale - next.Height));
                cr.PaintWithAlpha (progress);
                cr.Restore ();
            }
        }

 protected override void OnPaint(PaintEventArgs e)
 {
     base.OnPaint(e);
     using (System.Drawing.Graphics graphics = e.Graphics)
     {
         using (Win32Surface surface = new Win32Surface(graphics.GetHdc()))
         {
             using (Context context = new Context(surface))
             {
                 context.LineWidth = 2.0;
                 context.SetSourceColor(this.bugColor);
                 context.MoveTo(7.0, 64.0);
                 context.CurveTo(1.0, 47.0, 2.0, 46.0, 9.0, 51.0);
                 context.MoveTo(25.0, 80.0);
                 context.CurveTo(10.0, 73.0, 11.0, 70.0, 14.0, 63.0);
                 context.MoveTo(10.0, 41.0);
                 context.CurveTo(2.0, 36.0, 1.0, 33.0, 1.0, 26.0);
                 context.LineWidth = 1.0;
                 context.MoveTo(1.0, 26.0);
                 context.CurveTo(5.0, 23.0, 7.0, 18.0, 12.0, 17.0);
                 context.LineTo(12.0, 14.0);
                 context.Stroke();
                 context.MoveTo(30.0, 74.0);
                 context.CurveTo(14.0, 64.0, 10.0, 48.0, 11.0, 46.0);
                 context.LineTo(10.0, 45.0);
                 context.LineTo(10.0, 40.0);
                 context.CurveTo(13.0, 37.0, 15.0, 35.0, 19.0, 34.0);
                 context.Stroke();
             }
         }
     }
 }

        protected override void ClippedRender (Context cr)
        {
            if (!color_set || ChangeOnRender) {
                color = CairoExtensions.RgbToColor ((uint)rand.Next (0, 0xffffff));
                color_set = true;
            }

            CairoExtensions.RoundedRectangle (cr, 0, 0, RenderSize.Width, RenderSize.Height, 5);
	    cr.SetSourceColor (color);
            cr.Fill ();
        }

		protected override void DrawBackground (Context context, Gdk.Rectangle region)
		{
			LayoutRoundedRectangle (context, region);
			context.Clip ();

			context.SetSourceColor (CairoExtensions.ParseColor ("D3E6FF"));
			context.Paint ();

			context.Save ();
			context.Translate (region.X + region.Width / 2.0, region.Y + region.Height);

			using (var rg = new RadialGradient (0, 0, 0, 0, 0, region.Height * 1.2)) {
				var color = CairoExtensions.ParseColor ("E5F0FF");
				rg.AddColorStop (0, color);
				color.A = 0;
				rg.AddColorStop (1, color);

				context.Scale (region.Width / (double)region.Height, 1.0);
				context.SetSource (rg);
				context.Paint ();
			}

			context.Restore ();

			LayoutRoundedRectangle (context, region, -3, -3, 2);
			context.SetSourceRGBA (1, 1, 1, 0.4);
			context.LineWidth = 1;
			context.StrokePreserve ();

			context.Clip ();

			int boxSize = 11;
			int x = region.Left + (region.Width % boxSize) / 2;
			for (; x < region.Right; x += boxSize) {
				context.MoveTo (x + 0.5, region.Top);
				context.LineTo (x + 0.5, region.Bottom);
			}

			int y = region.Top + (region.Height % boxSize) / 2;
			y += boxSize / 2;
			for (; y < region.Bottom; y += boxSize) {
				context.MoveTo (region.Left, y + 0.5);
				context.LineTo (region.Right, y + 0.5);
			}

			context.SetSourceRGBA (1, 1, 1, 0.2);
			context.Stroke ();

			context.ResetClip ();
		}

        public override void Render(Context cr)
        {
            if (!CanResize) {
                return;
            }

            var selected_color = CairoExtensions.GdkRGBAToCairoColor (Window.StyleContext.GetColor (StateFlags.Selected));
            var grad = new LinearGradient (0, 0, 0, Allocation.Height);

            selected_color.A = 0.4;
            grad.AddColorStop (0, selected_color);
            selected_color.A = 1.0;
            grad.AddColorStop (1, selected_color);

            cr.SetSource (grad);
            cr.LineWidth = 1.0;
            cr.Rectangle (0.5, 0.5, Allocation.Width - 1, Allocation.Height - 1);
            cr.Stroke ();

            selected_color.A = 0.5;
            cr.SetSourceColor (selected_color);

            double handle_size = 8;
            double ty = 0.5 + Allocation.Height - handle_size - 3;
            double tx = 0.5 + (Window.Direction == TextDirection.Ltr
                ? Allocation.Width - handle_size - 3
                : 3);

            cr.Translate (tx, ty);

            for (double i = 0; i < 3; i++) {
                if (Window.Direction == TextDirection.Ltr) {
                    cr.MoveTo (i * 3, handle_size);
                    cr.LineTo (handle_size, i * 3);
                } else {
                    cr.MoveTo (0, i * 3);
                    cr.LineTo (handle_size - i * 3, handle_size);
                }
            }

            cr.Stroke ();

            cr.Translate (-tx, -ty);
        }

		public CellRendererSurface (int width, int height)
		{
			// TODO: Respect cell padding (Xpad and Ypad).
			SetFixedSize (width, height);

			transparent = new Cairo.ImageSurface (Cairo.Format.ARGB32, width, height);
			Cairo.Color gray = new Cairo.Color (.75, .75, .75);

			// Create checkerboard background	
			int grid_width = 4;

			using (Cairo.Context g = new Cairo.Context (transparent)) {
				g.SetSourceColor (new Cairo.Color (1, 1, 1));
				g.Paint ();

				for (int y = 0; y < height; y += grid_width)
					for (int x = 0; x < width; x += grid_width)
						if ((x / grid_width % 2) + (y / grid_width % 2) == 1)
							g.FillRectangle (new Cairo.Rectangle (x, y, grid_width, grid_width), gray);
			}	
		}

        public virtual void Render(Context cr, Gdk.Rectangle area, Color color, bool showEmptyStars, bool isHovering,
            int hoverValue, double fillOpacity, double hoverFillOpacity, double strokeOpacity)
        {
            if (Value == MinRating && !isHovering && !showEmptyStars) {
                return;
            }

            cr.Save ();

            Cairo.Color fill_color = color;
            fill_color.A = fillOpacity;
            Cairo.Color stroke_color = fill_color;
            stroke_color.A = strokeOpacity;
            Cairo.Color hover_fill_color = fill_color;
            hover_fill_color.A = hoverFillOpacity;

            double x, y;
            ComputePosition (area, out x, out y);

            cr.LineWidth = 1.0;
            cr.Translate (0.5, 0.5);

            for (int i = MinRating + 1, s = isHovering || showEmptyStars ? MaxRating : Value; i <= s; i++, x += Size) {
                bool fill = i <= Value && Value > MinRating;
                bool hover_fill = i <= hoverValue && hoverValue > MinRating;
                double scale = fill || hover_fill ? Size : Size - 2;
                double ofs = fill || hover_fill ? 0 : 1;

                for (int p = 0, n = star_plot.GetLength (0); p < n; p++) {
                    double px = x + ofs + star_plot[p, 0] * scale;
                    double py = y + ofs + star_plot[p, 1] * scale;
                    if (p == 0) {
                        cr.MoveTo (px, py);
                    } else {
                        cr.LineTo (px, py);
                    }
                }
                cr.ClosePath ();

                if (fill || hover_fill) {
                    if (!isHovering || hoverValue >= Value) {
                        cr.SetSourceColor (fill ? fill_color : hover_fill_color);
                    } else {
                        cr.SetSourceColor (hover_fill ? fill_color : hover_fill_color);
                    }
                    cr.Fill ();
                } else {
                    cr.SetSourceColor (stroke_color);
                    cr.Stroke ();
                }
            }
            cr.Restore ();
        }

        protected override void OnMouseMove(object o, Gtk.MotionNotifyEventArgs args, Cairo.PointD point)
        {
            Document doc = PintaCore.Workspace.ActiveDocument;

            if (mouse_button <= 0) {
                last_point = point_empty;
                return;
            }

            int x = (int)point.X;
            int y = (int)point.Y;

            if (last_point.Equals (point_empty))
                last_point = new Point (x, y);

            if (doc.Workspace.PointInCanvas (point))
                surface_modified = true;

            ImageSurface surf = doc.CurrentUserLayer.Surface;

            using (Context g = new Context (surf)) {
                g.AppendPath (doc.Selection.SelectionPath);
                g.FillRule = FillRule.EvenOdd;
                g.Clip ();

                g.Antialias = UseAntialiasing ? Antialias.Subpixel : Antialias.None;

                // Adding 0.5 forces cairo into the correct square:
                // See https://bugs.launchpad.net/bugs/672232
                g.MoveTo (last_point.X + 0.5, last_point.Y + 0.5);
                g.LineTo (x + 0.5, y + 0.5);

                // Right-click is erase to background color, left-click is transparent
                if (mouse_button == 3)
                    g.SetSourceColor (PintaCore.Palette.SecondaryColor);
                else
                    g.Operator = Operator.Clear;

                g.LineWidth = BrushWidth;
                g.LineJoin = LineJoin.Round;
                g.LineCap = LineCap.Round;

                g.Stroke ();
            }

            Gdk.Rectangle r = GetRectangleFromPoints (last_point, new Point (x, y));

            if (doc.Workspace.IsPartiallyOffscreen (r)) {
                doc.Workspace.Invalidate ();
            } else {
                doc.Workspace.Invalidate (doc.ClampToImageSize (r));
            }

            last_point = new Point (x, y);
        }

		protected override void OnMouseMove (object o, Gtk.MotionNotifyEventArgs args, Cairo.PointD point)
		{
			Document doc = PintaCore.Workspace.ActiveDocument;

			if ((args.Event.State & Gdk.ModifierType.Button1Mask) == Gdk.ModifierType.Button1Mask) {
				outline_color = PintaCore.Palette.PrimaryColor;
				fill_color = PintaCore.Palette.SecondaryColor;
			} else if ((args.Event.State & Gdk.ModifierType.Button3Mask) == Gdk.ModifierType.Button3Mask) {
				outline_color = PintaCore.Palette.SecondaryColor;
				fill_color = PintaCore.Palette.PrimaryColor;
			} else {
				last_point = point_empty;
				return;
			}

			int x = (int)point.X;
			int y = (int)point.Y;

			if (last_point.Equals (point_empty)) {
				last_point = new Point (x, y);
				return;
			}

			if (doc.Workspace.PointInCanvas (point))
				surface_modified = true;

			doc.ToolLayer.Clear ();
			ImageSurface surf = doc.ToolLayer.Surface;

			using (Context g = new Context (surf)) {
				doc.Selection.Clip(g);

				g.Antialias = UseAntialiasing ? Antialias.Subpixel : Antialias.None;

				g.SetDash(DashPatternBox.GenerateDashArray(dashPattern, BrushWidth), 0.0);

				if (path != null) {
					g.AppendPath (path);
					(path as IDisposable).Dispose ();
				} else {
					g.MoveTo (x, y);
				}
					
				g.LineTo (x, y);

				path = g.CopyPath ();
				
				g.ClosePath ();
				g.LineWidth = BrushWidth;
				g.FillRule = FillRule.EvenOdd;

				if (FillShape && StrokeShape) {
					g.SetSourceColor (fill_color);
					g.FillPreserve ();
					g.SetSourceColor (outline_color);
					g.Stroke ();
				} else if (FillShape) {
					g.SetSourceColor (outline_color);
					g.FillPreserve();
					g.SetSourceColor (outline_color);
					g.Stroke();
				} else {
					g.SetSourceColor (outline_color);
					g.Stroke ();
				}
			}

			doc.Workspace.Invalidate ();

			last_point = new Point (x, y);
		}

		protected override void OnMouseUp (Gtk.DrawingArea canvas, Gtk.ButtonReleaseEventArgs args, Cairo.PointD point)
		{
			Document doc = PintaCore.Workspace.ActiveDocument;
            doc.ToolLayer.Clear ();
			doc.ToolLayer.Hidden = true;

			ImageSurface surf = doc.CurrentUserLayer.Surface;
			using (Context g = new Context (surf)) {
				g.AppendPath (doc.Selection.SelectionPath);
				g.FillRule = FillRule.EvenOdd;
				g.Clip ();

				g.Antialias = UseAntialiasing ? Antialias.Subpixel : Antialias.None;

				g.SetDash(DashPatternBox.GenerateDashArray(dashPattern, BrushWidth), 0.0);

				if (path != null) {
					g.AppendPath (path);
					(path as IDisposable).Dispose ();
					path = null;
				}

				g.ClosePath ();
				g.LineWidth = BrushWidth;
				g.FillRule = FillRule.EvenOdd;

				if (FillShape && StrokeShape) {
					g.SetSourceColor (fill_color);
					g.FillPreserve ();
					g.SetSourceColor (outline_color);
					g.Stroke ();
				} else if (FillShape) {
					g.SetSourceColor (outline_color);
					g.FillPreserve();
					g.SetSourceColor (outline_color);
					g.Stroke();
				} else {
					g.SetSourceColor (outline_color);
					g.Stroke ();
				}
			}

			if (surface_modified)
				PintaCore.History.PushNewItem (new SimpleHistoryItem (Icon, Name, undo_surface, doc.CurrentUserLayerIndex));
			else if (undo_surface != null)
				(undo_surface as IDisposable).Dispose ();

			surface_modified = false;

			doc.Workspace.Invalidate ();
		}

        public override void DrawListBackground (Context cr, Gdk.Rectangle alloc, Color color)
        {
            color.A = Context.FillAlpha;
	    cr.SetSourceColor (color);
            cr.Rectangle (alloc.X, alloc.Y, alloc.Width, alloc.Height);
            cr.Fill ();
        }