C# CGContext.DrawLinearGradient方法代码示例

        public override void Draw(RectangleF bounds, CGContext context, UIView view)
        {
            UIColor.White.SetFill ();
            context.FillRect (bounds);

            context.DrawLinearGradient (
                gradient,
                new PointF (bounds.Left, bounds.Top),
                new PointF (bounds.Left, bounds.Bottom),
                CGGradientDrawingOptions.DrawsAfterEndLocation
            );

            UIColor.DarkGray.SetColor ();
            view.DrawString (
                this.Label,
                new RectangleF (10, 10, bounds.Width / 2, 10),
                captionFont,
                UILineBreakMode.TailTruncation
            );

            UIColor.Black.SetColor ();
            view.DrawString (
                this.Number.ToString (),
                new RectangleF (bounds.Width / 2, 10, (bounds.Width / 2) - 10, 10),
                amountFont,
                UILineBreakMode.TailTruncation,
                UITextAlignment.Right
            );
        }

		public override void Draw(RectangleF bounds, CGContext context, UIView view)
		{
			UIColor.White.SetFill();
			context.FillRect(bounds);
			
			context.DrawLinearGradient(gradient, new PointF(bounds.Left, bounds.Top), new PointF(bounds.Left, bounds.Bottom), CGGradientDrawingOptions.DrawsAfterEndLocation);
			
			UIColor.DarkGray.SetColor();
			view.DrawString(Caption, new RectangleF(10, 10, bounds.Width - 20, TextHeight(bounds)), _CaptionFont, UILineBreakMode.WordWrap);
		}

 protected override void DrawGradient(RectangleF rect, CGContext context)
 {
     context.DrawLinearGradient(new CGGradient(CGColorSpace.CreateDeviceRGB(),
                                               new CGColor[] {
         TintColor.CGColor,
         TintColor.Darken(TintDarkenFactor).CGColor
     }),
                                new PointF(0.5f, rect.Top),
                                new PointF(0.5f, rect.Bottom), 0);
 }

		public void DrawContentView(RectangleF rect, CGContext context, UITableViewElementCell cell)
		{
			context.SaveState();
			float r = 0;
			float g = 0;
			float b = 0;

			var gradient = new CGGradient(CGColorSpace.CreateDeviceRGB(), new float[] { r, g, b, 0.20f, r, g, b, 0.40f }, new float[] { 0, 1 });			
			context.DrawLinearGradient(gradient, new PointF(rect.Left, rect.Top), new PointF(rect.Left, rect.Bottom), CGGradientDrawingOptions.DrawsBeforeStartLocation);

			context.RestoreState();
		}

        public override void Draw(RectangleF bounds, CGContext context, UIView view)
        {
            UIColor.White.SetFill ();
            context.FillRect (bounds);

            context.DrawLinearGradient (gradient, new PointF (bounds.Left, bounds.Top), new PointF (bounds.Left, bounds.Bottom), CGGradientDrawingOptions.DrawsAfterEndLocation);

            UIColor.Black.SetColor ();
            view.DrawString("Assigned to: " + this.User, new RectangleF(10, 5, bounds.Width-20, 7), nameFont,UILineBreakMode.TailTruncation);

            UIColor.DarkGray.SetColor();
            view.DrawString(this.Text, new RectangleF(10, 30, bounds.Width - 20, TextHeight(bounds) ), descriptionFont, UILineBreakMode.WordWrap);
        }

		public override void Draw (RectangleF bounds, CGContext context, UIView view)
		{
			UIColor.White.SetFill ();
			context.FillRect (bounds);
			
			context.DrawLinearGradient (gradient, new PointF (bounds.Left, bounds.Top), new PointF (bounds.Left, bounds.Bottom), CGGradientDrawingOptions.DrawsAfterEndLocation);
			
			UIColor.Black.SetColor ();
			view.DrawString(this.From, new RectangleF(10, 5, bounds.Width/2, 10 ), fromFont, UILineBreakMode.TailTruncation);
			
			UIColor.Brown.SetColor ();
			view.DrawString(this.Sent, new RectangleF(bounds.Width/2, 5, (bounds.Width/2) - 10, 10 ), dateFont, UILineBreakMode.TailTruncation, UITextAlignment.Right);
			
			UIColor.DarkGray.SetColor();
			view.DrawString(this.Subject, new RectangleF(10, 30, bounds.Width - 20, TextHeight(bounds) ), subjectFont, UILineBreakMode.WordWrap);
		}

        public override void Draw(RectangleF bounds, CGContext context, UIView view)
        {
            UIColor.White.SetFill ();
            context.FillRect (bounds);

            context.DrawLinearGradient (
                gradient,
                new PointF (bounds.Left, bounds.Top),
                new PointF (bounds.Left, bounds.Bottom),
                CGGradientDrawingOptions.DrawsAfterEndLocation
            );

            //UIColor.Black.SetColor ();
            ColorHelper.GetGPLightPurple ().SetColor ();
            view.DrawString (
                this.Label,
                new RectangleF (10, 10, bounds.Width, 20),
                captionFont,
                UILineBreakMode.TailTruncation
            );
        }

        public override void Draw(RectangleF bounds, CGContext context, UIView view)
        {
            //			string name = CultureInfo.CurrentCulture.Name;
            //			NumberFormatInfo nfi = new CultureInfo (name, true).NumberFormat;
            //			if (name == "en-ZA") {
            //				nfi.CurrencyDecimalSeparator = ",";
            //				nfi.CurrencyGroupSeparator = " ";
            //
            //				nfi.NumberDecimalSeparator = ",";
            //				nfi.NumberGroupSeparator = " ";
            //			}

            UIColor.White.SetFill ();
            context.FillRect (bounds);

            context.DrawLinearGradient (
                gradient,
                new PointF (bounds.Left, bounds.Top),
                new PointF (bounds.Left, bounds.Bottom),
                CGGradientDrawingOptions.DrawsAfterEndLocation
            );

            UIColor.DarkGray.SetColor ();
            view.DrawString (
                this.Label,
                new RectangleF (20, 10, bounds.Width / 2, 10),
                captionFont,
                UILineBreakMode.TailTruncation
            );

            UIColor.Black.SetColor ();
            view.DrawString (
                this.Amount.ToString ("N2"),
                new RectangleF (bounds.Width / 2, 10, (bounds.Width / 2) - 10, 10),
                amountFont,
                UILineBreakMode.TailTruncation,
                UITextAlignment.Right
            );
        }

		public override void Draw (RectangleF bounds, CGContext context, UIView view)
		{
			UIColor.White.SetFill ();
			context.FillRect (bounds);
			
			context.DrawLinearGradient (gradient, new PointF (bounds.Left, bounds.Top), new PointF (bounds.Left, bounds.Bottom), CGGradientDrawingOptions.DrawsAfterEndLocation);
			
			UIColor.Black.SetColor ();
			((NSString) From).DrawString (new RectangleF (10, 5, bounds.Width / 2, 10 ), NSStringDrawingOptions.TruncatesLastVisibleLine | NSStringDrawingOptions.UsesLineFragmentOrigin, new UIStringAttributes ()
			{
				Font = fromFont,
			}, null);
			
			UIColor.Brown.SetColor ();
			((NSString) Sent).DrawString (new RectangleF (bounds.Width / 2, 5, (bounds.Width / 2) - 10, 10), NSStringDrawingOptions.TruncatesLastVisibleLine | NSStringDrawingOptions.UsesLineFragmentOrigin, new UIStringAttributes ()
			{
				Font = dateFont,
				ParagraphStyle = new NSMutableParagraphStyle ()
				{
					Alignment = UITextAlignment.Right,
				},
			}, null);
			
			UIColor.DarkGray.SetColor();
			((NSString) Subject).DrawString (new RectangleF (10, 30, bounds.Width - 20, TextHeight (bounds)), NSStringDrawingOptions.TruncatesLastVisibleLine | NSStringDrawingOptions.UsesLineFragmentOrigin, new UIStringAttributes ()
			{
				Font = subjectFont,
				ParagraphStyle = new NSMutableParagraphStyle ()
				{
					LineBreakMode = UILineBreakMode.WordWrap,
				},
			}, null);
		}

		public void DrawElementView(RectangleF rect, CGContext context, UITableViewElementCell cell)
		{
			context.DrawLinearGradient(gradient, new PointF(rect.Left, rect.Top), new PointF(rect.Left, rect.Bottom), CGGradientDrawingOptions.DrawsBeforeStartLocation);
			cell.ShouldDrawBorder = true;
		}

        private void DrawShine(CGContext context, RectangleF rect)
        {
            context.SaveState ();

            context.BeginPath ();
            var maxY = MakePath (context, rect);
            context.Clip ();

            /*var locations = new float[] { 0.0f, 0.5f };
            var components = new float[] { 0.92f, 0.92f, 0.92f, 1.0f, 0.82f, 0.82f, 0.82f, 0.4f };*/

            var locations = new float[] { 0f, 0.4f, 0.5f, 0.5f, 0.6f, 1.0f };
            var colors = new UIColor[] {
                UIColor.FromWhiteAlpha (1.0f, 0.885f),
                UIColor.FromWhiteAlpha (1.0f, 0.45f),
                UIColor.FromWhiteAlpha (1.0f, 0.23f),
                UIColor.FromWhiteAlpha (1.0f, 0.10f),
                UIColor.FromRGBA (0f, 0f, 0f, 0.13f),
                UIColor.FromRGBA (0f, 0f, 0f, 0.13f)
            };
            var components = GetComponents (colors);

            var darkLoc = new float[] { 0.5f, 1.0f };
            var darkComp = new float[] { 0.08f, 0.08f, 0.08f, 0.6f, 0.18f, 0.18f, 0.18f, 0.2f };

            using (var cspace = CGColorSpace.CreateDeviceRGB ())
            using (var darkGrad = new CGGradient (cspace, darkComp, darkLoc))
            using (var gradient = new CGGradient (cspace, components, locations)) {

                PointF sPoint = new PointF (0f, 0f),
                    ePoint = new PointF (0f, maxY);
                context.DrawLinearGradient (gradient, sPoint, ePoint, 0);
            }

            context.RestoreState ();
        }

        private void DrawLinearGradient(CGContext context, RectangleF rect, CGColor startColor, CGColor  endColor)
        {
            CGColorSpace colorSpace = CGColorSpace.CreateDeviceRGB ();
            float [] locations = { 0.0f, 1.0f };

            CGColor [] colors = new CGColor[] { startColor, endColor };

            CGGradient gradient = new CGGradient (colorSpace, colors, locations);

            PointF startPoint = new PointF (rect.GetMidX (), rect.GetMinY ());
            PointF endPoint = new PointF (rect.GetMidX (), rect.GetMaxY ());

            context.SaveState ();
            context.AddPath (UIBezierPath.FromRoundedRect (rect, 10).CGPath);
            context.Clip ();
            context.DrawLinearGradient (gradient, startPoint, endPoint, 0);
            context.RestoreState ();
        }

        public override void DrawInContext(CGContext ctx)
        {
            base.DrawInContext (ctx);

            var knobFrame = CGRect.Inflate(Bounds, -2.0f, -2.0f);

            UIBezierPath knobPath = UIBezierPath.FromRoundedRect((CGRect)knobFrame, (nfloat)knobFrame.Height / 2.0f);

            // 1) fill - with a subtle shadow
            ctx.SetShadow(new CGSize(0, 1), 1.0f, UIColor.Gray.CGColor);
            ctx.SetFillColor( UIColor.White.CGColor);
            ctx.AddPath( knobPath.CGPath);
            ctx.FillPath ();

            // 2) outline
            ctx.SetStrokeColor(UIColor.Gray.CGColor);
            ctx.SetLineWidth((nfloat)0.5f);
            ctx.AddPath(knobPath.CGPath);
            ctx.StrokePath ();

            // 3) inner gradient
            var rect = CGRect.Inflate(knobFrame, -2.0f, -2.0f);
            var clipPath = UIBezierPath.FromRoundedRect ((CGRect)rect, (nfloat)rect.Height / 2.0f);

            CGGradient myGradient;
            CGColorSpace myColorspace;

            nfloat[] locations = { 0.0f, 1.0f };
            nfloat[] components = { 0.0f, 0.0f, 0.0f , 0.15f,  // Start color
                0.0f, 0.0f, 0.0f, 0.05f }; // End color

            myColorspace = CGColorSpace.CreateDeviceRGB (); // CGColorSpaceCreateDeviceRGB();
            myGradient = new CGGradient( myColorspace, components, locations);

            CGPoint startPoint = new CGPoint((float)rect.GetMidX(), (float)rect.GetMinY());
            CGPoint endPoint = new CGPoint((float)rect.GetMidX(), (float)rect.GetMaxY());

            ctx.SaveState ();
            ctx.AddPath( clipPath.CGPath);
            ctx.Clip ();
            ctx.DrawLinearGradient( (CGGradient)myGradient, (CGPoint)startPoint, (CGPoint)endPoint, (CGGradientDrawingOptions)0);

            myGradient.Dispose ();
            myColorspace.Dispose();
            ctx.RestoreState();

            // 4) highlight
            if (Highlighted)
            {
                // fill
                ctx.SetFillColor(UIColor.FromWhiteAlpha((nfloat)0.0f, (nfloat)0.1f).CGColor);
                ctx.AddPath( knobPath.CGPath);
                ctx.FillPath();
            }
            //
            //			if (Highlighted)
            //				ctx.SetFillColor (UIColor.Yellow.CGColor);
            //			else
            //				ctx.SetFillColor (UIColor.Red.CGColor);
            //
            //			ctx.FillRect (Bounds);
        }

		public void DrawElementView(RectangleF rect, CGContext context, UITableViewElementCell cell)
		{
			var gradientFrame = rect;
			
			var shineFrame = gradientFrame;
			shineFrame.Y += 1;
			shineFrame.X += 1;
			shineFrame.Width -= 2;
			shineFrame.Height = (shineFrame.Height / 2);

			CGColorSpace colorSpace = CGColorSpace.CreateDeviceRGB();

			var gradient = new CGGradient(
			    colorSpace,
			    new float[] { 0f, 0f,0f, 0.70f, 
							  0f, 0f, 0f, 0.40f},
				new float[] { 0, 1 } );

			var shineGradient = new CGGradient(
			    colorSpace,
			    new float[] { 1f, 1f, 1f, 0.80f, 
							  1f, 1f, 1f, 0.10f},
				new float[] { 0, 1 } );
			
			if (Cell != null && Cell.Highlighted)
			{
				context.SetFillColorWithColor(HighlightColor.CGColor);
			}
			else
			{
				context.SetFillColorWithColor(CellBackgroundColor.CGColor);
			}
			context.FillRect(rect);
	
			context.DrawLinearGradient(gradient, new PointF(gradientFrame.Left, gradientFrame.Top), new PointF(gradientFrame.Left, gradientFrame.Bottom), CGGradientDrawingOptions.DrawsAfterEndLocation);		
			context.DrawLinearGradient(shineGradient, new PointF(shineFrame.Left, shineFrame.Top), new PointF(shineFrame.Left, shineFrame.Bottom), CGGradientDrawingOptions.DrawsAfterEndLocation);
		}

    public override void DrawInContext(CGContext context)
    {
        // The clipping rects we plan to use, which also defines the location and span of each gradient
        var clips = new RectangleF []
        {
            new RectangleF(10, 30, 60, 90),
            new RectangleF(90, 30, 60, 90),
            new RectangleF(170, 30, 60, 90),
            new RectangleF(250, 30, 60, 90),
            new RectangleF(30, 140, 120, 120),
            new RectangleF(170, 140, 120, 120),
            new RectangleF(30, 280, 120, 120),
            new RectangleF(170, 280, 120, 120),
        };

        // Linear Gradients
        PointF start, end;

        // Clip to area to draw the gradient, and draw it. Since we are clipping, we save the graphics state
        // so that we can revert to the previous larger area.
        context.SaveState();
        context.ClipToRect(clips[0]);

        // A linear gradient requires only a starting & ending point.
        // The colors of the gradient are linearly interpolated along the line segment connecting these two points
        // A gradient location of 0 means that color is expressed fully at the 'start' point
        // a location of 1 means that color is expressed fully at the 'end' point.
        // The gradient fills outwards perpendicular to the line segment connectiong start & end points
        // (which is why we need to clip the context, or the gradient would fill beyond where we want it to).
        // The gradient options (last) parameter determines what how to fill the clip area that is "before" and "after"
        // the line segment connecting start & end.
        start = demoLGStart(clips[0]);
        end = demoLGEnd(clips[0]);
        context.DrawLinearGradient(gradient, start, end, 0);
        context.RestoreState();

        // Same as above for each combination of CGGradientDrawingOptions.DrawsBeforeStartLocation & CGGradientDrawingOptions.DrawsAfterEndLocation

        context.SaveState();
        context.ClipToRect(clips[1]);
        start = demoLGStart(clips[1]);
        end = demoLGEnd(clips[1]);
        context.DrawLinearGradient(gradient, start, end, CGGradientDrawingOptions.DrawsBeforeStartLocation);
        context.RestoreState();

        context.SaveState();
        context.ClipToRect(clips[2]);
        start = demoLGStart(clips[2]);
        end = demoLGEnd(clips[2]);
        context.DrawLinearGradient(gradient, start, end, CGGradientDrawingOptions.DrawsAfterEndLocation);
        context.RestoreState();

        context.SaveState();
        context.ClipToRect(clips[3]);
        start = demoLGStart(clips[3]);
        end = demoLGEnd(clips[3]);
        context.DrawLinearGradient(gradient, start, end, CGGradientDrawingOptions.DrawsBeforeStartLocation | CGGradientDrawingOptions.DrawsAfterEndLocation);
        context.RestoreState();

        // Radial Gradients

        float startRadius, endRadius;

        // Clip to area to draw the gradient, and draw it. Since we are clipping, we save the graphics state
        // so that we can revert to the previous larger area.
        context.SaveState();
        context.ClipToRect(clips[4]);

        // A radial gradient requires a start & end point as well as a start & end radius.
        // Logically a radial gradient is created by linearly interpolating the center, radius and color of each
        // circle using the start and end point for the center, start and end radius for the radius, and the color ramp
        // inherant to the gradient to create a set of stroked circles that fill the area completely.
        // The gradient options specify if this interpolation continues past the start or end points as it does with
        // linear gradients.
        start = end = demoRGCenter(clips[4]);
        startRadius = demoRGInnerRadius(clips[4]);
        endRadius = demoRGOuterRadius(clips[4]);
        context.DrawRadialGradient(gradient, start, startRadius, end, endRadius, 0);
        context.RestoreState();

        // Same as above for each combination of CGGradientDrawingOptions.DrawsBeforeStartLocation & CGGradientDrawingOptions.DrawsAfterEndLocation

        context.SaveState();
        context.ClipToRect(clips[5]);
        start = end = demoRGCenter(clips[5]);
        startRadius = demoRGInnerRadius(clips[5]);
        endRadius = demoRGOuterRadius(clips[5]);
        context.DrawRadialGradient(gradient, start, startRadius, end, endRadius, CGGradientDrawingOptions.DrawsBeforeStartLocation);
        context.RestoreState();

        context.SaveState();
        context.ClipToRect(clips[6]);
        start = end = demoRGCenter(clips[6]);
        startRadius = demoRGInnerRadius(clips[6]);
        endRadius = demoRGOuterRadius(clips[6]);
        context.DrawRadialGradient(gradient, start, startRadius, end, endRadius, CGGradientDrawingOptions.DrawsAfterEndLocation);
        context.RestoreState();

        context.SaveState();
        context.ClipToRect(clips[7]);
//.........这里部分代码省略.........