C# Cairo.Context类代码示例

        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 GtkGraphDrawer(Context g, Context gh, ImageSurface srfc)
 {
     this.g = g;
     this.gh = gh;
     this.srfc = srfc;
     gh.Antialias = Antialias.Subpixel;
 }

        public void Render(DrawingArea area, SettingsModel settings)
        {
            var width = area.Allocation.Width;
            var height = area.Allocation.Height;

            var kaleidoscope = _factory.Get (settings.Type);
            var rootNode = kaleidoscope.Generate (
                settings.GeometyWidth,
                settings.ImageUri,
                width, height);

            ImageSurface surface = new ImageSurface(Format.Argb32, width, height);

            using (var context = new Context (surface)) {
                context.Translate(width / 2, height / 2);
                rootNode.Render (context);
            }
            rootNode.Geometry.Dispose ();

            using (Context context = Gdk.CairoHelper.Create (area.GdkWindow)) {
                context.Rectangle(0, 0, width, height);
                context.SetSource(surface);
                context.Fill();
                context.GetTarget ().Dispose ();
            }
            surface.Dispose ();
        }

        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.
                }
            }
        }

        protected override void DrawGraduations(Context gr, PointD pStart, PointD pEnd)
        {
            Rectangle r = ClientRectangle;
            Foreground.SetAsSource (gr);

            gr.LineWidth = 2;
            gr.MoveTo(pStart);
            gr.LineTo(pEnd);

            gr.Stroke();
            gr.LineWidth = 1;

            double sst = unity * SmallIncrement;
            double bst = unity * LargeIncrement;

            PointD vBar = new PointD(0, sst);
            for (double x = Minimum; x <= Maximum - Minimum; x += SmallIncrement)
            {
                double lineLength = r.Height / 3;
                if (x % LargeIncrement != 0)
                    lineLength /= 3;
                PointD p = new PointD(pStart.X + x * unity, pStart.Y);
                gr.MoveTo(p);
                gr.LineTo(new PointD(p.X, p.Y + lineLength));
            }
            gr.Stroke();
        }

        public static ImageSurface Create (Gdk.Pixbuf pixbuf, bool disposePixbuf)
        {
            if (pixbuf == null || pixbuf.Handle == IntPtr.Zero) {
                return null;
            }

            if (!PlatformDetection.IsWindows) {
                try {
                    return new PixbufImageSurface (pixbuf, disposePixbuf);
                } catch {
                    return null;
                }
            } else {
                // FIXME:
                // Windows has some trouble running the PixbufImageSurface, so as a
                // workaround a slower but working version of this factory method is
                // implemented. One day we can come back and optimize this by finding
                // out what's causing the PixbufImageSurface to result in access
                // violations when the object is disposed.
                ImageSurface target = new ImageSurface (Format.ARGB32, pixbuf.Width, pixbuf.Height);
                Context context = new Context (target);
                try {
                    Gdk.CairoHelper.SetSourcePixbuf (context, pixbuf, 0, 0);
                    context.Paint ();
                } finally {
                    ((IDisposable)context).Dispose ();
                    if (disposePixbuf) {
                        ((IDisposable)pixbuf).Dispose ();
                    }
                }

                return target;
            }
        }

		private ImageInfo CreateBlur (ImageInfo source)
		{
			double scale = Math.Max (256 / (double) source.Bounds.Width,
						 256 / (double) source.Bounds.Height);

			Gdk.Rectangle small = new Gdk.Rectangle (0, 0,
								(int) Math.Ceiling (source.Bounds.Width * scale),
								(int) Math.Ceiling (source.Bounds.Height * scale));

			MemorySurface image = new MemorySurface (Format.Argb32,
								 small.Width,
								 small.Height);

			Context ctx = new Context (image);
			//Pattern solid = new SolidPattern (0, 0, 0, 0);
			//ctx.Source = solid;
			//ctx.Paint ();
			//solid.Destroy ();
			ctx.Matrix = source.Fit (small);
			ctx.Operator = Operator.Source;
			Pattern p = new SurfacePattern (source.Surface);
			ctx.Source = p;
			//Log.Debug (small);
			ctx.Paint ();
			p.Destroy ();
			((IDisposable)ctx).Dispose ();
			Gdk.Pixbuf normal = MemorySurface.CreatePixbuf (image);
			Gdk.Pixbuf blur = PixbufUtils.Blur (normal, 3);
			ImageInfo overlay = new ImageInfo (blur);
			blur.Dispose ();
			normal.Dispose ();
			image.Destroy ();
			return overlay;
		}

  protected override FlowReturn OnTransformIp (Gst.Buffer buf) {
    if (!buf.IsWritable)
      return FlowReturn.Error;

    Cairo.ImageSurface img = new Cairo.ImageSurface (buf.Data, Cairo.Format.Rgb24, width, height, width*4);

    using (Cairo.Context context = new Cairo.Context (img)) {
      double dx = (double) ( (buf.Timestamp / Clock.MSecond) % 2180) / 5;
      context.Save ();
      context.Scale (width / 640.0, height / 480.0);
      context.MoveTo (300, 10 + dx);
      context.LineTo (500 - dx, 400);
      context.LineWidth = 4.0;
      context.Color = new Color (0, 0, 1.0);
      context.Stroke();
      context.Restore ();

      if (lastX != -1 && lastY != -1) {
        context.Color = new Color (1.0, 0, 0);
        context.Translate (lastX, lastY);
        context.Scale (Math.Min (width / 640.0, height / 480.0), Math.Min (width / 640.0, height / 480.0));
        context.Arc (0, 0, 10.0, 0.0, 2 * Math.PI);
        context.Fill();
      }
    }

    img.Destroy ();
    return base.OnTransformIp (buf);
  }

 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();
             }
         }
     }
 }

 public override void Run()
 {
     ICollection<double> chapters = this.Theory.Chapters;
     StripCanvasSize scs = this.Manager.GenerateStripCanvasSize (chapters.Count);
     double dw = scs.CanvasSize.Width;
     double dh = scs.CanvasSize.Height;
     using (PdfSurface surface = new PdfSurface (this.Manager.OutputFile, scs.TotalWidth, scs.TotalHeight)) {
         using (Context ctx = new Context (surface)) {
             int index = 0x00;
             IPoint3 p;
             foreach (double chapter in chapters) {
                 p = scs.GetCanvasOffset (index);
                 ctx.Save ();
                 ctx.Translate (p.X, p.Y);
                 ctx.Rectangle (0.0d, 0.0d, dw, dh);
                 ctx.Stroke ();
                 this.Theory.Time = chapter;
                 CairoEngine engine = new CairoEngine (this.Theory);
                 engine.Context = ctx;
                 engine.Process ();
                 ctx.Restore ();
                 index++;
             }
         }
     }
 }

        public override void DrawArrow(Context cr, Gdk.Rectangle alloc, SortType type)
        {
            cr.LineWidth = 1;
            cr.Translate (0.5, 0.5);
            double x1 = alloc.X;
            double x3 = alloc.X + alloc.Width / 2.0;
            double x2 = x3 + (x3 - x1);
            double y1 = alloc.Y;
            double y2 = alloc.Bottom;

            if (type == SortType.Ascending) {
                cr.MoveTo (x1, y1);
                cr.LineTo (x2, y1);
                cr.LineTo (x3, y2);
                cr.LineTo (x1, y1);
            } else {
                cr.MoveTo (x3, y1);
                cr.LineTo (x2, y2);
                cr.LineTo (x1, y2);
                cr.LineTo (x3, y1);
            }

            cr.SetSourceColor (Colors.GetWidgetColor (GtkColorClass.Base, StateType.Normal));
            cr.FillPreserve ();
            cr.SetSourceColor (Colors.GetWidgetColor (GtkColorClass.Text, StateType.Normal));
            cr.Stroke ();
            cr.Translate (-0.5, -0.5);
        }

        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.Color = color;
                cr.Stroke ();
            }
        }

 public SketchPad(IPuzzleQueryResolver resolver)
 {
     ImageSurface imsu = new ImageSurface(Format.Argb32,0x01,0x01);
     this.subcontext = new Context(imsu);
     this.AddEvents((int) (Gdk.EventMask.PointerMotionMask|Gdk.EventMask.ButtonPressMask|Gdk.EventMask.ButtonReleaseMask));
     this.resolver = resolver;
 }

		protected void UpdateRectangle (PointD point)
		{
			if (!is_drawing)
				return;

			Document doc = PintaCore.Workspace.ActiveDocument;

			Rectangle r = PointsToRectangle (shape_origin, point);
			Rectangle dirty;

			doc.ToolLayer.Clear ();
			doc.ToolLayer.Hidden = false;

			using (Context g = new Context (doc.ToolLayer.Surface)) {
				g.Antialias = Antialias.Subpixel;

				dirty = g.FillStrokedRectangle (r, new Color (0, 0.4, 0.8, 0.1), new Color (0, 0, 0.9), 1);
				dirty = dirty.Clamp ();

				doc.Workspace.Invalidate (last_dirty.ToGdkRectangle ());
				doc.Workspace.Invalidate (dirty.ToGdkRectangle ());
				
				last_dirty = dirty;
			}
		}

		protected override Gdk.Rectangle OnMouseMove (Context g, Color strokeColor, ImageSurface surface,
		                                              int x, int y, int lastX, int lastY)
		{
			// Cairo does not support a single-pixel-long single-pixel-wide line
			if (x == lastX && y == lastY && g.LineWidth == 1 &&
			    PintaCore.Workspace.ActiveWorkspace.PointInCanvas (new PointD(x,y))) {
				surface.Flush ();

				ColorBgra source = surface.GetColorBgraUnchecked (x, y);
				source = UserBlendOps.NormalBlendOp.ApplyStatic (source, strokeColor.ToColorBgra ());
				surface.SetColorBgra (source, x, y);
				surface.MarkDirty ();

				return new Gdk.Rectangle (x - 1, y - 1, 3, 3);
			}

			g.MoveTo (lastX + 0.5, lastY + 0.5);
			g.LineTo (x + 0.5, y + 0.5);
			g.StrokePreserve ();

			Gdk.Rectangle dirty = g.FixedStrokeExtents ().ToGdkRectangle ();

			// For some reason (?!) we need to inflate the dirty
			// rectangle for small brush widths in zoomed images
			dirty.Inflate (1, 1);

			return dirty;
		}