BitmapDataExtensionsBeginDrawQuadraticCurves(IReadWriteBitmapData, Pen, IEnumerablePointF, DrawingOptions, AsyncConfig) Method

public static IAsyncResult BeginDrawQuadraticCurves(
	this IReadWriteBitmapData bitmapData,
	Pen pen,
	IEnumerable<PointF> points,
	DrawingOptions? drawingOptions = null,
	AsyncConfig? asyncConfig = null
)

<ExtensionAttribute>
Public Shared Function BeginDrawQuadraticCurves ( 
	bitmapData As IReadWriteBitmapData,
	pen As Pen,
	points As IEnumerable(Of PointF),
	Optional drawingOptions As DrawingOptions = Nothing,
	Optional asyncConfig As AsyncConfig = Nothing
) As IAsyncResult

public:
[ExtensionAttribute]
static IAsyncResult^ BeginDrawQuadraticCurves(
	IReadWriteBitmapData^ bitmapData, 
	Pen^ pen, 
	IEnumerable<PointF>^ points, 
	DrawingOptions^ drawingOptions = nullptr, 
	AsyncConfig^ asyncConfig = nullptr
)

[<ExtensionAttribute>]
static member BeginDrawQuadraticCurves : 
        bitmapData : IReadWriteBitmapData * 
        pen : Pen * 
        points : IEnumerable<PointF> * 
        ?drawingOptions : DrawingOptions * 
        ?asyncConfig : AsyncConfig 
(* Defaults:
        let _drawingOptions = defaultArg drawingOptions null
        let _asyncConfig = defaultArg asyncConfig null
*)
-> IAsyncResult 

Parameters

bitmapData  IReadWriteBitmapData

The IReadWriteBitmapData instance to draw on.

pen  Pen

The Pen that determines the characteristics of the curves.

points  IEnumerablePointF

The points of the curves to draw.

drawingOptions  DrawingOptions  (Optional)

A DrawingOptions instance that specifies the drawing options to use. If , then the default options are used. This parameter is optional.
Default value: .

asyncConfig  AsyncConfig  (Optional)

The configuration of the asynchronous operation such as parallelization, cancellation, reporting progress, etc. When Progress is set in this parameter, then this library always passes a DrawingOperation instance to the generic methods of the IAsyncProgress interface. This parameter is optional.
Default value: .

Return Value

Usage Note

In the points parameter 0 or odd number of points are expected.

When points has at least three items, the first three points define the first quadratic curve. Each additional two points define a new quadratic curve, where the last point of the previous curve is the starting point of the next curve.

This method draws quadratic Bézier curves. A quadratic Bézier curve is defined by three points: the starting point, the control point, and the end point. To draw cubic Bézier curves, you can use the BeginDrawBeziers methods. In fact, this method transforms the quadratic curves into cubic Bézier curves internally.

This method tries to use a shortcut to draw the curves directly, which is faster than creating a Path and adding the curves to it. A shortcut is possible when the specified pen has a width between 0.25 and 1, it uses a solid Brush with an opaque color, and if drawingOptions is either , or its FastThinLines is enabled in drawingOptions, it specifies that no anti-aliasing and no alpha blending is required, the transformation is the identity matrix, and neither Quantizer nor Ditherer is specified.

When no shortcut can be used and the same curves are drawn repeatedly, creating a Path with PreferCaching enabled can provide a better performance.

In .NET Framework 4.0 and above you can use also the DrawQuadraticCurvesAsync methods.

To finish the operation and to get the exception that occurred during the operation you have to call the EndDrawQuadraticCurves method.

This method is not a blocking call even if the MaxDegreeOfParallelism property of the asyncConfig parameter is 1.

If the curves are drawn by using a shortcut, then the operation is executed synchronously, it cannot be canceled, it is not parallelized, and there is no progress reporting, regardless of the asyncConfig parameter.

Reference