研究Direct2D已經有一段時間了，也寫了一個系列的文章 Direct2D ，是基於Windows API Code Pack 1.1。在前文 Direct2D教程VIII——幾何（Geometry）對象的運算，本系列的終結篇 中介紹，由於Windows API Code Pack 1.1有錯誤問題，加上長時間沒有更新（可以看出是2010年推出的），於是終止了該系列的教程。
在網上尋尋覓覓Windows API Code Pack 1.1的替代品。找到了SharpDX。SharpDX官網：http://www.sharpdx.org/。
下圖是官網截圖，SharpDX自詡是最好的DirectX的開發包（不僅僅包括Direct2D，還包括DirectX 3D等等）
我在學習了一段時間后，感覺上，它的幫助文檔和MSDN相比，缺少了示例教程。雖然在論壇上，也有不少人提供了各自的示例代碼，但僅僅是代碼，而且顯得凌亂分散。示例代碼之間缺少連貫性，給學習者造成了障礙。
下面的截圖是調用Geometry對象的Combine方法的效果圖（也就是在前文中，Windows API Code Pack 1.1中出現的錯誤的地方）。
於是決定用SharpDX來繼續Direct2D的系列教程
下載開發包，並在項目中引用
在官網上下載完整的安裝包（目前的版本是2.5.0），安裝后，可以找到如下的動態庫的目錄。可以看出支持.net 2.0到.net 4.0，支持WinRT、WP8等。
本系列的教程選擇 DirectX11_1-net40 ，雙擊打開后，看到如下的目錄
針對不同的內容，有不同的DLL文件。本系列的文章主要是介紹Direct2D，因此只要在項目中引入SharpDX.DLL、SharpDX.DXGI.DLL、SharpDX.Direct2D1.DLL即可。
下面是基本的示例代碼，把Direct2D的繪制的內容繪制到控件上。后面的示例類都是繼承於此類。
Imports DX = SharpDX
Imports D2D = SharpDX.Direct2D1
Imports WIC = SharpDX.WIC
Imports DDW = SharpDX.DirectWrite
Imports DXGI = SharpDX.DXGI
Public Class clsSharpDXSampleBase
Protected _D2DFactory As D2D. Factory
Protected _RenderTarget As D2D. WindowRenderTarget
Public Sub CreateDeviceResource(Target As Control)
_D2DFactory = New D2D. Factory
Dim P As New D2D. PixelFormat(DXGI. Format.B8G8R8A8_UNorm, D2D. AlphaMode.Ignore)
Dim H As New D2D. HwndRenderTargetProperties
H.Hwnd = Target.Handle
H.PixelSize = New DX. Size2(Target.Width, Target.Height)
H.PresentOptions = SharpDX.Direct2D1. PresentOptions.None
Dim R As New D2D. RenderTargetProperties(D2D. RenderTargetType.Hardware, _
P, 0, 0, _
D2D. RenderTargetUsage.None, _
D2D. FeatureLevel.Level_DEFAULT)
_RenderTarget = New D2D. WindowRenderTarget(_D2DFactory, R, H)
End Sub
Public Sub Render()
If Not _renderTarget Is Nothing Then
_RenderTarget.BeginDraw()
_RenderTarget.Clear(DX.Color.BlueViolet.ToColor4)
_RenderTarget.EndDraw()
End If
End Sub
End Class
和Windows API Code Pack1.1類似，先定義Factory對象，再定義RenderTarget對象的各個參數。PixelFormat對象定義像素格式和Alpha模式；HwndRenderTargetProperties對象定義了綁定控件的Hwnd和Size及PresentOptions（呈現方式）；RenderTargetProperties對象定義了呈現模式（Hardware，硬件級；Software，軟件級；WIC不支持硬件級），像素模式（PixelFormat），DpiX和DpiY（0表示采用系統的默認值），RenderTargetUsage和FeatureLevel（這兩個參數都用默認值）
不同的是，Windows API Code Pack 1.1中用的是Factory對象的CreateHwndRenderTarget方法創建RenderTarget，而SharpDX用RenderTarget對象的New方法創建RenderTarget對象，習慣就好，無所謂優劣。（類似的，SharpDX用對象的New方法對應很多的Create****方法）
下圖是上面示例代碼的效果圖
SharpDX中的顏色
在SharpDX中，對顏色對象加強了功能。用Color、Color3、Color4對象表示顏色。
其中，Color4對象是基礎的顏色對象，在使用顏色的場合中，用的都是Color4對象。Color4對象用Red、Green、Blue、Alpha分量表示顏色。下面是Color4的一些方法與函數的原型定義
Public Sub New(value As Single)
Public Sub New(red As Single, green As Single, blue As Single, alpha As Single)
Public Sub New(value As DX. Vector4)
Public Sub New(value As DX. Vector3, alpha As Single)
Public Sub New(rgba As UInteger)
Public Sub New(rgba As Integer)
Public Sub New(values As Single())
Public Sub New(color As DX. Color3)
Public Sub New(color As DX. Color3, alpha As Single)
Public Function ToBgra() As Integer
Public Sub ToBgra( ByRef r As Byte, ByRef g As Byte, ByRef b As Byte, ByRef a As Byte)
Public Function ToRgba() As Integer
Public Function ToVector3() As DX. Vector3
Public Function ToVector4() As DX. Vector4
Public Function ToArray() As Single()
Public Shared Sub Add( ByRef left As DX. Color4, ByRef right As DX. Color4, ByRef result As DX. Color4)
Public Shared Function Add(left As DX. Color4, right As DX. Color4) As DX. Color4
Public Shared Sub Subtract( ByRef left As DX. Color4, ByRef right As DX. Color4, ByRef result As DX. Color4)
Public Shared Function Subtract(left As DX. Color4, right As DX. Color4) As DX. Color4
Public Shared Sub Modulate( ByRef left As DX. Color4, ByRef right As DX. Color4, ByRef result As DX. Color4)
Public Shared Function Modulate(left As DX. Color4, right As DX. Color4) As DX. Color4
Public Shared Sub Scale( ByRef value As DX. Color4, scale As Single, ByRef result As DX. Color4)
Public Shared Function Scale(value As DX. Color4, scale As Single) As DX. Color4
Public Shared Sub Negate( ByRef value As DX. Color4, ByRef result As DX. Color4)
Public Shared Function Negate(value As DX. Color4) As DX. Color4
Public Shared Sub Clamp( ByRef value As DX. Color4, ByRef min As DX. Color4, ByRef max As DX. Color4, ByRef result As DX. Color4)
Public Shared Function Clamp(value As DX. Color4, min As DX. Color4, max As DX. Color4) As DX. Color4
Public Shared Sub Lerp( ByRef start As DX. Color4, ByRef [end] As DX. Color4, amount As Single, ByRef result As DX. Color4)
Public Shared Function Lerp(start As DX. Color4, [end] As DX. Color4, amount As Single) As DX. Color4
Public Shared Sub SmoothStep( ByRef start As DX. Color4, ByRef [end] As DX. Color4, amount As Single, ByRef result As DX. Color4)
Public Shared Function SmoothStep(start As DX. Color4, [end] As DX. Color4, amount As Single) As DX. Color4
Public Shared Sub Max( ByRef left As DX. Color4, ByRef right As DX. Color4, ByRef result As DX. Color4)
Public Shared Function Max(left As DX. Color4, right As DX. Color4) As DX. Color4
Public Shared Sub Min( ByRef left As DX. Color4, ByRef right As DX. Color4, ByRef result As DX. Color4)
Public Shared Function Min(left As DX. Color4, right As DX. Color4) As DX. Color4
Public Shared Sub AdjustContrast( ByRef value As DX. Color4, contrast As Single, ByRef result As DX. Color4)
Public Shared Function AdjustContrast(value As DX. Color4, contrast As Single) As DX. Color4
Public Shared Sub AdjustSaturation( ByRef value As DX. Color4, saturation As Single, ByRef result As DX. Color4)
Public Shared Function AdjustSaturation(value As DX. Color4, saturation As Single) As DX. Color4
從上面的原型定義可以看出，Color4增加了很多有意思的方法，解釋如下：
Add：兩個顏色相加，各個分量分別相加，等同於運算符 + 。
Subtract：兩個顏色相減，各個分量分別相減，等同於運算符 – 。
Modulate：兩個顏色相乘，各個分量分別相乘，等同於運算符 * 。
Sacle：縮放顏色，顏色的每個分量分別和參數scale相乘
Negate：取顏色的反色，用1減去每個顏色的分量
Clamp：限定顏色分量的范圍，如果分量小於Min的分量，則取Min的分量；如果分量大於Max分量，則取Max分量
Lerp：按比例取兩個顏色之間的插值部分，參數amount表示比例
SmoothStep：按比例取兩個顏色之間的插值部分，參數amount表示比例。和Lerp相比，Lerp是線性插值，SmoothStep是二次插值
Max：各取兩個顏色分量的最大值的顏色
Min：各取兩個顏色分量的最小值的顏色
AdjustContrast：調節對比度，參數contrast是對比度比例參數
AdjustSaturation：調節飽和度，參數Saturation是飽和度比例參數
看了代碼后，發現Color4並沒有對Red、Green、Blue、Alpha分量進行限制（正常值是0-1），這樣在用上面的方法時，很容易出現分量超出范圍的情況（小於0，大於1）。但是，似乎系統內部進行了處理，在實際使用時，超出的部分會自動處理成0或1（小於0處理成0，大於1處理成1）。
Color對象和Color4對象類似，分量是用Byte表示（0-255）；Color3對象用Red、Green、Blue分量表示顏色。
Color對象和Color3對象都有ToColor4方法轉換為Color4對象
Color對象還包含了眾多內置靜態的顏色，如BlueViolet等，這樣就可以很方便的用英文來表示顏色，而不需要記住這些顏色對應的Integer的值。
從上面的來看，SharpDX的確要比Windows API Code Pack 1.1方便了很多。
接下來，會陸續把前文中的例子轉換為SharpDX后，再出新的SharpDX教程