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);
}
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);
}
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);
}
