private void SkCanvasView_OnPaintSurface(object sender, SKPaintSurfaceEventArgs e)
        {
            var skImageInfo = e.Info;
            var skSurface   = e.Surface;
            var skCanvas    = skSurface.Canvas;

            var skCanvasWidth  = skImageInfo.Width;
            var skCanvasHeight = skImageInfo.Height;

            skCanvas.Clear(SKColors.White);

            // Draw gradient rainbow Color spectrum
            using (var paint = new SKPaint())
            {
                paint.IsAntialias = true;

                // Initiate the primary Color list
                // picked up from Google Web Color Picker
                var colors = new SKColor[]
                {
                    new SKColor(255, 0, 0),                     // Red
                    new SKColor(255, 255, 0),                   // Yellow
                    new SKColor(0, 255, 0),                     // Green (Lime)
                    new SKColor(0, 255, 255),                   // Aqua
                    new SKColor(0, 0, 255),                     // Blue
                    new SKColor(255, 0, 255),                   // Fuchsia
                    new SKColor(255, 0, 0),                     // Red
                };

                // create the gradient shader between Colors
                using (var shader = SKShader.CreateLinearGradient(
                           new SKPoint(0, 0),
                           new SKPoint(skCanvasWidth, 0),
                           colors,
                           null,
                           SKShaderTileMode.Clamp))
                {
                    paint.Shader = shader;
                    skCanvas.DrawPaint(paint);
                }
            }

            // Draw darker gradient spectrum
            using (var paint = new SKPaint())
            {
                paint.IsAntialias = true;

                // Initiate the darkened primary color list
                var colors = new SKColor[]
                {
                    SKColors.Transparent,
                    SKColors.Black
                };

                // create the gradient shader
                using (var shader = SKShader.CreateLinearGradient(
                           new SKPoint(0, 0),
                           new SKPoint(0, skCanvasHeight),
                           colors,
                           null,
                           SKShaderTileMode.Clamp))
                {
                    paint.Shader = shader;
                    skCanvas.DrawPaint(paint);
                }
            }

            // Picking the Pixel Color values on the Touch Point

            // Represent the color of the current Touch point
            SKColor touchPointColor;

            //// Inefficient: causes memory overload errors
            //using (var skImage = skSurface.Snapshot())
            //{
            //	using (var skData = skImage.Encode(SKEncodedImageFormat.Webp, 100))
            //	{
            //		if (skData != null)
            //		{
            //			using (SKBitmap bitmap = SKBitmap.Decode(skData))
            //			{
            //				touchPointColor = bitmap.GetPixel(
            //									(int)_lastTouchPoint.X, (int)_lastTouchPoint.Y);
            //			}
            //		}
            //	}
            //}

            // Efficient and fast
            // https://forums.xamarin.com/discussion/92899/read-a-pixel-info-from-a-canvas
            // create the 1x1 bitmap (auto allocates the pixel buffer)
            using (SKBitmap bitmap = new SKBitmap(skImageInfo))
            {
                // get the pixel buffer for the bitmap
                IntPtr dstpixels = bitmap.GetPixels();

                // read the surface into the bitmap
                skSurface.ReadPixels(skImageInfo,
                                     dstpixels,
                                     skImageInfo.RowBytes,
                                     (int)_lastTouchPoint.X, (int)_lastTouchPoint.Y);

                // access the color
                touchPointColor = bitmap.GetPixel(0, 0);
            }

            // Painting the Touch point
            using (SKPaint paintTouchPoint = new SKPaint())
            {
                paintTouchPoint.Style       = SKPaintStyle.Fill;
                paintTouchPoint.Color       = SKColors.White;
                paintTouchPoint.IsAntialias = true;

                // Outer circle (Ring)
                var outerRingRadius =
                    ((float)skCanvasWidth / (float)skCanvasHeight) * (float)18;
                skCanvas.DrawCircle(
                    _lastTouchPoint.X,
                    _lastTouchPoint.Y,
                    outerRingRadius, paintTouchPoint);

                // Draw another circle with picked color
                paintTouchPoint.Color = touchPointColor;

                // Outer circle (Ring)
                var innerRingRadius =
                    ((float)skCanvasWidth / (float)skCanvasHeight) * (float)12;
                skCanvas.DrawCircle(
                    _lastTouchPoint.X,
                    _lastTouchPoint.Y,
                    innerRingRadius, paintTouchPoint);
            }

            // Set selected color
            PickedColor = touchPointColor.ToFormsColor();
            PickedColorChanged?.Invoke(this, PickedColor);
        }
Beispiel #2
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        private void SkCanvasView_OnPaintSurface(object sender, SKPaintSurfaceEventArgs e)
        {
            var skImageInfo = e.Info;
            var skSurface   = e.Surface;
            var skCanvas    = skSurface.Canvas;

            var skCanvasWidth  = skImageInfo.Width;
            var skCanvasHeight = skImageInfo.Height;

            skCanvas.Clear(SKColors.White);

            // Draw gradient rainbow Color spectrum
            using (var paint = new SKPaint())
            {
                paint.IsAntialias = true;

                System.Collections.Generic.List <SKColor> colors = new System.Collections.Generic.List <SKColor>();
                ColorList.ForEach((color) => { colors.Add(Color.FromHex(color).ToSKColor()); });

                // create the gradient shader between Colors
                using (var shader = SKShader.CreateLinearGradient(
                           new SKPoint(0, 0),
                           ColorListDirection == ColorListDirection.Horizontal ?
                           new SKPoint(skCanvasWidth, 0) : new SKPoint(0, skCanvasHeight),
                           colors.ToArray(),
                           null,
                           SKShaderTileMode.Clamp))
                {
                    paint.Shader = shader;
                    skCanvas.DrawPaint(paint);
                }
            }

            // Draw darker gradient spectrum
            using (var paint = new SKPaint())
            {
                paint.IsAntialias = true;

                // Initiate the darkened primary color list
                var colors = GetGradientOrder();

                // create the gradient shader
                using (var shader = SKShader.CreateLinearGradient(
                           new SKPoint(0, 0),
                           ColorListDirection == ColorListDirection.Horizontal ?
                           new SKPoint(0, skCanvasHeight) : new SKPoint(skCanvasWidth, 0),
                           colors,
                           null,
                           SKShaderTileMode.Clamp))
                {
                    paint.Shader = shader;
                    skCanvas.DrawPaint(paint);
                }
            }

            // Picking the Pixel Color values on the Touch Point

            // Represent the color of the current Touch point
            SKColor touchPointColor;

            // Efficient and fast
            // https://forums.xamarin.com/discussion/92899/read-a-pixel-info-from-a-canvas
            // create the 1x1 bitmap (auto allocates the pixel buffer)
            using (SKBitmap bitmap = new SKBitmap(skImageInfo))
            {
                // get the pixel buffer for the bitmap
                IntPtr dstpixels = bitmap.GetPixels();

                // read the surface into the bitmap
                skSurface.ReadPixels(skImageInfo,
                                     dstpixels,
                                     skImageInfo.RowBytes,
                                     (int)_lastTouchPoint.X, (int)_lastTouchPoint.Y);

                // access the color
                touchPointColor = bitmap.GetPixel(0, 0);
            }

            // Painting the Touch point
            using (SKPaint paintTouchPoint = new SKPaint())
            {
                paintTouchPoint.Style       = SKPaintStyle.Fill;
                paintTouchPoint.Color       = SKColors.White;
                paintTouchPoint.IsAntialias = true;

                var valueToCalcAgainst = (skCanvasWidth > skCanvasHeight) ? skCanvasWidth : skCanvasHeight;

                var pointerCircleDiameterUnits = PointerCircleDiameterUnits;          // 0.6 (Default)
                pointerCircleDiameterUnits = (float)pointerCircleDiameterUnits / 10f; //  calculate 1/10th of that value
                var pointerCircleDiameter = (float)(valueToCalcAgainst * pointerCircleDiameterUnits);

                // Outer circle of the Pointer (Ring)
                skCanvas.DrawCircle(
                    _lastTouchPoint.X,
                    _lastTouchPoint.Y,
                    pointerCircleDiameter / 2, paintTouchPoint);

                // Draw another circle with picked color
                paintTouchPoint.Color = touchPointColor;

                var pointerCircleBorderWidthUnits = PointerCircleBorderUnits;             // 0.3 (Default)
                var pointerCircleBorderWidth      = (float)pointerCircleDiameter *
                                                    (float)pointerCircleBorderWidthUnits; // Calculate against Pointer Circle

                // Inner circle of the Pointer (Ring)
                skCanvas.DrawCircle(
                    _lastTouchPoint.X,
                    _lastTouchPoint.Y,
                    ((pointerCircleDiameter - pointerCircleBorderWidth) / 2), paintTouchPoint);
            }

            // Set selected color
            PickedColor = touchPointColor.ToFormsColor();
            PickedColorChanged?.Invoke(this, PickedColor);
        }
Beispiel #3
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        private void SkCanvasView_OnPaintSurface(object sender, SKPaintSurfaceEventArgs e)
        {
            var skImageInfo = e.Info;
            var skSurface   = e.Surface;
            var skCanvas    = skSurface.Canvas;

            var skCanvasWidth  = skImageInfo.Width;
            var skCanvasHeight = skImageInfo.Height;

            skCanvas.Clear(SKColors.White);

            // Draw gradient rainbow Color spectrum
            using (var paint = new SKPaint())
            {
                paint.IsAntialias = true;

                // Initiate the base Color list
                ColorTypeConverter converter = new ColorTypeConverter();
                System.Collections.Generic.List <SKColor> colors = new System.Collections.Generic.List <SKColor>();
                foreach (var color in BaseColorList)
                {
                    colors.Add(((Color)converter.ConvertFromInvariantString(color.ToString())).ToSKColor());
                }

                // create the gradient shader between base Colors
                using (var shader = SKShader.CreateLinearGradient(
                           new SKPoint(0, 0),
                           ColorFlowDirection == ColorFlowDirection.Horizontal ?
                           new SKPoint(skCanvasWidth, 0) : new SKPoint(0, skCanvasHeight),
                           colors.ToArray(),
                           null,
                           SKShaderTileMode.Clamp))
                {
                    paint.Shader = shader;
                    skCanvas.DrawPaint(paint);
                }
            }

            // Draw secondary gradient color spectrum
            using (var paint = new SKPaint())
            {
                paint.IsAntialias = true;

                // Initiate gradient color spectrum style layer
                var colors = GetSecondaryLayerColors(ColorSpectrumStyle);

                // create the gradient shader between secondary colors
                using (var shader = SKShader.CreateLinearGradient(
                           new SKPoint(0, 0),
                           ColorFlowDirection == ColorFlowDirection.Horizontal ?
                           new SKPoint(0, skCanvasHeight) : new SKPoint(skCanvasWidth, 0),
                           colors,
                           null,
                           SKShaderTileMode.Clamp))
                {
                    paint.Shader = shader;
                    skCanvas.DrawPaint(paint);
                }
            }

            if (!_checkPointerInitPositionDone)
            {
                var x = ((float)skCanvasWidth * (float)PointerRingPositionXUnits);
                var y = ((float)skCanvasHeight * (float)PointerRingPositionYUnits);

                _lastTouchPoint = new SKPoint(x, y);

                _checkPointerInitPositionDone = true;
            }

            // Picking the Pixel Color values on the Touch Point

            // Represent the color of the current Touch point
            SKColor touchPointColor;

            // Efficient and fast
            // https://forums.xamarin.com/discussion/92899/read-a-pixel-info-from-a-canvas
            // create the 1x1 bitmap (auto allocates the pixel buffer)
            using (SKBitmap bitmap = new SKBitmap(skImageInfo))
            {
                // get the pixel buffer for the bitmap
                IntPtr dstpixels = bitmap.GetPixels();

                // read the surface into the bitmap
                skSurface.ReadPixels(skImageInfo,
                                     dstpixels,
                                     skImageInfo.RowBytes,
                                     (int)_lastTouchPoint.X, (int)_lastTouchPoint.Y);

                // access the color
                touchPointColor = bitmap.GetPixel(0, 0);
            }

            // Painting the Touch point
            using (SKPaint paintTouchPoint = new SKPaint())
            {
                paintTouchPoint.Style       = SKPaintStyle.Fill;
                paintTouchPoint.Color       = SKColors.White;
                paintTouchPoint.IsAntialias = true;

                var canvasLongestLength = (skCanvasWidth > skCanvasHeight)
                        ? skCanvasWidth : skCanvasHeight;

                // Calculate 1/10th of the units value for scaling
                var pointerRingDiameterUnitsScaled = (float)PointerRingDiameterUnits / 10f;
                // Calculate against Longest Length of Canvas
                var pointerRingDiameter = (float)canvasLongestLength
                                          * pointerRingDiameterUnitsScaled;

                // Outer circle of the Pointer (Ring)
                skCanvas.DrawCircle(
                    _lastTouchPoint.X,
                    _lastTouchPoint.Y,
                    (pointerRingDiameter / 2), paintTouchPoint);

                // Draw another circle with picked color
                paintTouchPoint.Color = touchPointColor;

                // Calculate against Pointer Circle
                var pointerRingInnerCircleDiameter = (float)pointerRingDiameter
                                                     * (float)PointerRingBorderUnits;

                // Inner circle of the Pointer (Ring)
                skCanvas.DrawCircle(
                    _lastTouchPoint.X,
                    _lastTouchPoint.Y,
                    ((pointerRingDiameter
                      - pointerRingInnerCircleDiameter) / 2), paintTouchPoint);
            }

            // Set selected color
            PickedColor = touchPointColor.ToFormsColor();
            PickedColorChanged?.Invoke(this, PickedColor);
        }