C# Paint类代码示例

      // assumptions for pixel snapping: 
      // - the drawing context itself is pixel snapped
      // - all strokes have same thickness
      // - the thickness is a whole number


      #region ELLIPSES
      /// <summary>See <c>WpfExtensions</c> for details.</summary>
      public static void DrawEllipse(DrawingContext dc, Paint paint, Point center, double radiusX, double radiusY, bool snapToPixel) {
         // get brush and stroke resources
         if (paint == null) return;
         var fill = paint.Fill;
         var hasFill = (fill != null);
         var strokes = paint.GetStrokePens().ToArray();
         var numStrokes = strokes.Length;
         if (!hasFill && numStrokes == 0) return;

         var halfThickness = Math.Round(numStrokes > 0? strokes[0].Thickness : 0.0) / 2;
         if (snapToPixel) {
            center = new Point(center.X + halfThickness, center.Y + halfThickness);
         }

         if (numStrokes > 0) {
            for (var i = 0; i < numStrokes - 1; i++) {
               dc.DrawEllipse(null, strokes[i], center, radiusX, radiusY);
               radiusX = (radiusX - 2 * halfThickness).Max(0);
               radiusY = (radiusY - 2 * halfThickness).Max(0);
            }
            dc.DrawEllipse(fill, strokes[numStrokes - 1], center, radiusX, radiusY);
         } else {
            dc.DrawEllipse(fill, null, center, radiusX, radiusY);
         }

      }

        public SlidingTabStrip1(Context context, IAttributeSet attrs)
            : base(context, attrs)
        {
            SetWillNotDraw(false);

            float density = Resources.DisplayMetrics.Density;

            TypedValue outValue = new TypedValue();
            context.Theme.ResolveAttribute(Android.Resource.Attribute.ColorForeground, outValue, true);
            int themeForeGround = outValue.Data;
            mDefaultBottomBorderColor = SetColorAlpha(themeForeGround, DEFAULT_BOTTOM_BORDER_COLOR_ALPHA);

            mDefaultTabColorizer = new SimpleTabColorizer1();
            mDefaultTabColorizer.IndicatorColors = INDICATOR_COLORS;
            mDefaultTabColorizer.DividerColors = DIVIDER_COLORS;

            mBottomBorderThickness = (int)(DEFAULT_BOTTOM_BORDER_THICKNESS_DIPS * density);
            mBottomBorderPaint = new Paint();
            mBottomBorderPaint.Color = GetColorFromInteger(0xC5C5C5); //Gray

            mSelectedIndicatorThickness = (int)(SELECTED_INDICATOR_THICKNESS_DIPS * density);
            mSelectedIndicatorPaint = new Paint();

            mDividerHeight = DEFAULT_DIVIDER_HEIGHT;
            mDividerPaint = new Paint();
            mDividerPaint.StrokeWidth = (int)(DEFAULT_DIVIDER_THICKNESS_DIPS * density);
        }

		public CircleImageView(Context context, IAttributeSet attrs, int defStyle)
			: base(context, attrs, defStyle)
		{

			// init paint
			paint = new Paint();
			paint.AntiAlias = true;

			paintBorder = new Paint();
			paintBorder.AntiAlias = true;

			// load the styled attributes and set their properties
			TypedArray attributes = context.ObtainStyledAttributes(attrs, Resource.Styleable.CircularImageView, defStyle, 0);

			if (attributes.GetBoolean(Resource.Styleable.CircularImageView_border, true))
			{
				int defaultBorderSize = (int)(4 * context.Resources.DisplayMetrics.Density+ 0.5f);
				BorderWidth = attributes.GetDimensionPixelOffset(Resource.Styleable.CircularImageView_border_width, defaultBorderSize);
				BorderColor = attributes.GetColor(Resource.Styleable.CircularImageView_border_color, Color.White);
			}

			if (attributes.GetBoolean(Resource.Styleable.CircularImageView_shadow, false))
			{
				addShadow();
			}
		}

		void Initialize ()
		{
			mPaint = new Paint ();
			mPaint.Color = Color.Black;
			mPaint.AntiAlias = true;
			mPaint.SetStyle (Paint.Style.Fill);
		}

 protected void DrawShape(Canvas canvas)
 {
   Paint paint = new Paint();
   paint.Color = Color;
   switch (Shape)
   {
     case ShapeEnum.RectangleShape:
       canvas.DrawRect(0, 0, ShapeWidth, ShapeHeight, paint);
       break;
     case ShapeEnum.OvalShape:
       canvas.DrawOval(new RectF(0, 0, ShapeWidth, ShapeHeight), paint);
       break;
     case ShapeEnum.TriangleShape:
         Path path = new Path();
         path.MoveTo(ShapeWidth / 2, 0);
         path.LineTo(ShapeWidth, ShapeHeight);
         path.LineTo(0,ShapeHeight);
         path.Close();
       canvas.DrawPath(path, paint);
       break;
     default:
       canvas.DrawCircle(ShapeWidth / 2, ShapeHeight / 2, ShapeWidth / 2, paint); 
       break;
   }
 }

        //        Tile tile;
        public MapPlotter(int size)
        {
            this.size = size;

            defaultPaint = new Paint();
            defaultPaint.Fill = PlotterHelper.DEFAULT_COLOR;

            roadPaint = new Paint();
            roadPaint.StrokeCap = PenLineCap.Round;

            roadBorderPaint = new Paint();
            roadBorderPaint.Stroke = PlotterHelper.ROAD_BORDER_COLOR;
            roadBorderPaint.StrokeCap = PenLineCap.Round;

            grassPaint = new Paint();
            grassPaint.Fill = PlotterHelper.NATURE_GRASS_COLOR;

            waterPaint = new Paint();
            waterPaint.Fill = PlotterHelper.NATURE_WATER_COLOR;

            riverPaint = new Paint();
            riverPaint.Stroke = PlotterHelper.NATURE_RIVER_COLOR;
            riverPaint.StrokeCap = PenLineCap.Round;

            buildingPaint = new Paint();
        }

        protected override void OnDraw(Canvas canvas)
        {
            base.OnDraw (canvas);

            var r = new Rect ();
            this.GetLocalVisibleRect (r);

            var half = r.Width() / 2;
            var height = r.Height();

            var percentage = (this.Limit - Math.Abs(this.CurrentValue)) / this.Limit;


            var paint = new Paint()
            {
                Color = this.CurrentValue < 0 ? this.negativeColor : this.positiveColor,
                StrokeWidth = 5
            };

            paint.SetStyle(Paint.Style.Fill);

            if (this.CurrentValue < 0)
            {
                var start = (float)percentage * half;
                var size = half - start;
                canvas.DrawRect (new Rect ((int)start, 0, (int)(start + size), height), paint);
            }
            else
            {
                canvas.DrawRect (new Rect((int)half, 0, (int)(half + percentage * half), height), paint);
            }
        }

	    public BezelImageView(Context context, IAttributeSet attrs, int defStyle) : base(context, attrs, defStyle)
		{
			// Attribute initialization
	        var a = context.ObtainStyledAttributes(attrs, Resource.Styleable.BezelImageView, defStyle, 0);
	
	        mMaskDrawable = a.GetDrawable(Resource.Styleable.BezelImageView_maskDrawable);
	        if (mMaskDrawable == null) {
	            mMaskDrawable = Resources.GetDrawable(Resource.Drawable.bezel_mask);
	        }
	        mMaskDrawable.Callback = this;
	
	        mBorderDrawable = a.GetDrawable(Resource.Styleable.BezelImageView_borderDrawable);
	        if (mBorderDrawable == null) {
	            mBorderDrawable = Resources.GetDrawable(Resource.Drawable.bezel_border);
	        }
	        mBorderDrawable.Callback = this;
	
	        a.Recycle();
	
	        // Other initialization
	        mMaskedPaint = new Paint();
	        mMaskedPaint.SetXfermode(new PorterDuffXfermode(PorterDuff.Mode.SrcAtop));
	
	        mCopyPaint = new Paint();
		}

		// If you would like to create a circle of the image set pixels to half the width of the image.
		internal static   Bitmap GetRoundedCornerBitmap(Bitmap bitmap, int pixels)
		{
			Bitmap output = null;

			try
			{
				output = Bitmap.CreateBitmap(bitmap.Width, bitmap.Height, Bitmap.Config.Argb8888);
				Canvas canvas = new Canvas(output);

				Color color = new Color(66, 66, 66);
				Paint paint = new Paint();
				Rect rect = new Rect(0, 0, bitmap.Width, bitmap.Height);
				RectF rectF = new RectF(rect);
				float roundPx = pixels;

				paint.AntiAlias = true;
				canvas.DrawARGB(0, 0, 0, 0);
				paint.Color = color;
				canvas.DrawRoundRect(rectF, roundPx, roundPx, paint);

				paint.SetXfermode(new PorterDuffXfermode(PorterDuff.Mode.SrcIn));
				canvas.DrawBitmap(bitmap, rect, rect, paint);
			}
			catch (System.Exception err)
			{
				System.Console.WriteLine ("GetRoundedCornerBitmap Error - " + err.Message);
			}

			return output;
		}

			public SampleView (Context context) : base (context)
			{
				Focusable = true;

				mPaint = new Paint ();
				mPaint.AntiAlias = true;
			}

        public override void Draw(Android.Graphics.Canvas canvas)
        {
            base.Draw (canvas);

            Paint mBgPaints = new Paint ();
            mBgPaints.AntiAlias = true;
            mBgPaints.SetStyle (Paint.Style.Fill);
            mBgPaints.Color = Color.Blue;
            mBgPaints.StrokeWidth = 0.5f;

            Paint tPaint = new Paint ();
            tPaint.Alpha = 0;
            canvas.DrawColor (tPaint.Color);

            RectF mOvals = new RectF (40, 40, layout.MeasuredWidth - 40, layout.MeasuredHeight - 40);

            decimal total = 0;
            foreach (SecuritiesViewModel.PieChartValue value in securitiesViewModel.DataForPieChart ()) {
                total += value.amount;
            }

            if (total == 0) {
                return;
            }

            decimal degressPerAmount = 360 / total;
            decimal currentAngle = 0;
            foreach (SecuritiesViewModel.PieChartValue value in securitiesViewModel.DataForPieChart ()) {
                canvas.DrawArc (mOvals, (float)currentAngle, (float)(degressPerAmount * value.amount), true, mBgPaints);
                currentAngle += (degressPerAmount * value.amount);
                mBgPaints.SetARGB (255, new Random ().Next (256), new Random ().Next (256), new Random ().Next (256));
            }
        }

		public void applyFilterElements(Paint pPaint) {
			this.mSVGAttributes.getFloatAttribute(SVGConstants.ATTRIBUTE_X, true);
			List<ISVGFilterElement> svgFilterElements = this.mSVGFilterElements;
			for(int i = 0; i < svgFilterElements.Count; i++) {
				svgFilterElements[i].Apply(pPaint);
			}
		}

		static void test_alphagradients (Canvas canvas)
		{
			canvas.translate (20, 10);

			RectF r = new RectF (10, 10, 410, 30);
			Paint p = new Paint (), p2 = new Paint ();
			p2.setStyle (Paint.Style.STROKE);

			using (Shader shader = setgrad (r, 0xFF00FF00, 0x0000FF00))
				p.setShader (shader);
			canvas.drawRect (r, p);
			canvas.drawRect (r, p2);

			r.offset (0, r.height () + 4);
			using (Shader shader = setgrad(r, 0xFF00FF00, 0x00000000))
				p.setShader (shader);
			canvas.drawRect (r, p);
			canvas.drawRect (r, p2);

			r.offset (0, r.height () + 4);
			using (Shader shader = setgrad(r, 0xFF00FF00, 0x00FF0000))
				p.setShader (shader);
			canvas.drawRect (r, p);
			canvas.drawRect (r, p2);
		}

        private static void ApplyCustomTypeFace(Paint paint, Typeface tf, Android.Graphics.Color color)
        {
            int oldStyle;
            Typeface old = paint.Typeface;
            if (old == null)
            {
                oldStyle = 0;
            }
            else
            {
                oldStyle = (int)old.Style;
            }

            int fake = oldStyle & ~(int)tf.Style;
            if ((fake & (int)TypefaceStyle.Bold) != 0)
            {
                paint.FakeBoldText = true;
            }

            if ((fake & (int)TypefaceStyle.Italic) != 0)
            {
                paint.TextSkewX = -0.25f;
            }



            paint.SetARGB(color.A, color.R, color.G, color.B);

            paint.SetTypeface(tf);
        }

        public override void Draw(Android.Graphics.Canvas canvas)
        {
            base.Draw(canvas);

            var rect = new RectF(0,0,300,300);
            switch (TheShape)
            {
                case Shape.Circle:
                    canvas.DrawOval(rect, new Paint() { Color = Color.Aqua });
                    break;
                case Shape.Square:
                    canvas.DrawRect(rect, new Paint() { Color = Color.Red });
                    break;
                case Shape.Triangle:
                    var path = new Path();
                    path.MoveTo(rect.CenterX(), 0);
                    path.LineTo(0, rect.Height());
                    path.LineTo(rect.Width(), rect.Height());
                    path.Close();

                    var paint = new Paint() {Color = Color.Magenta};
                    paint.SetStyle(Paint.Style.Fill);
                    canvas.DrawPath(path, paint);
                    break;

                default:
                    throw new ArgumentOutOfRangeException();
            }
        }