Graphics.GetHalftonePalette Metode

Definisi

Ruang nama:

System.Drawing

Rakitan:

System.Drawing.Common.dll

Paket:

System.Drawing.Common v9.0.0-rc.2.24474.1

Sumber:

Graphics.cs

Mendapatkan handel ke palet halftone Windows saat ini.

public:
 static IntPtr GetHalftonePalette();

public static IntPtr GetHalftonePalette ();

static member GetHalftonePalette : unit -> nativeint

Public Shared Function GetHalftonePalette () As IntPtr

Mengembalikan

IntPtr

nativeint

Penunjuk internal yang menentukan handel ke palet.

Contoh

Contoh kode berikut dirancang untuk digunakan dengan Windows Forms, dan memerlukan PaintEventArgse, yang merupakan parameter penanganan aktivitas Paint. Kode melakukan tindakan berikut:

• Menentukan atribut DllImportAttribute interoperabilitas untuk file Dll Windows gdi32.dll, yang berisi fungsi GDI yang diperlukan.

• Menentukan fungsi SelectPalette dan RealizePalette di DLL tersebut sebagai eksternal.

• Membuat gambar dari file gambar yang ada SampImag.jpg (yang harus berada di folder yang sama dengan file kode contoh) dan menggambar gambar ke layar.

• Membuat variabel jenis pointer internal dan mengatur nilainya ke handel ke objek grafis dan ke palet halftone Windows saat ini.

• Memilih dan mewujudkan palet halftone.

• Membuat objek grafis baru menggunakan parameter hdc.

• Menggambar gambar lagi.

• Merilis handel ke konteks perangkat.

Hasilnya adalah dua penyajian gambar sampel: satu dengan palet 16-bit dan satu dengan palet 8-bit.

private:
   [System::Runtime::InteropServices::DllImportAttribute("gdi32.dll")]
   static IntPtr SelectPalette( IntPtr hdc, IntPtr htPalette, bool bForceBackground );

   [System::Runtime::InteropServices::DllImportAttribute("gdi32.dll")]
   static int RealizePalette( IntPtr hdc );

public:
   void GetHalftonePaletteVoid( PaintEventArgs^ e )
   {
      // Create and draw image.
      Image^ imageFile = Image::FromFile( "SampImag.jpg" );
      e->Graphics->DrawImage( imageFile, Point(0,0) );

      // Get handle to device context.
      IntPtr hdc = e->Graphics->GetHdc();

      // Get handle to halftone palette.
      IntPtr htPalette = Graphics::GetHalftonePalette();

      // Select and realize new palette.
      SelectPalette( hdc, htPalette, true );
      RealizePalette( hdc );

      // Create new graphics object.
      Graphics^ newGraphics = Graphics::FromHdc( hdc );

      // Draw image with new palette.
      newGraphics->DrawImage( imageFile, 300, 0 );

      // Release handle to device context.
      e->Graphics->ReleaseHdc( hdc );
   }

[System.Runtime.InteropServices.DllImportAttribute("gdi32.dll")]
private static extern IntPtr SelectPalette(
    IntPtr hdc,
    IntPtr htPalette,
    bool bForceBackground);
[System.Runtime.InteropServices.DllImportAttribute("gdi32.dll")]
private static extern int RealizePalette(IntPtr hdc);

private void GetHalftonePaletteVoid(PaintEventArgs e)
{
    // Create and draw image.
    Image imageFile = Image.FromFile("SampImag.jpg");
    e.Graphics.DrawImage(imageFile, new Point(0, 0));

    // Get handle to device context.
    IntPtr hdc = e.Graphics.GetHdc();

    // Get handle to halftone palette.
    IntPtr htPalette = Graphics.GetHalftonePalette();

    // Select and realize new palette.
    SelectPalette(hdc, htPalette, true);
    RealizePalette(hdc);

    // Create new graphics object.
    Graphics newGraphics = Graphics.FromHdc(hdc);

    // Draw image with new palette.
    newGraphics.DrawImage(imageFile, 300, 0);

    // Release handle to device context.
    e.Graphics.ReleaseHdc(hdc);
}

<System.Runtime.InteropServices.DllImportAttribute("gdi32.dll")> _
Private Shared Function SelectPalette(ByVal hdc As IntPtr, _
ByVal htPalette As IntPtr, ByVal bForceBackground As Boolean) As IntPtr
End Function

<System.Runtime.InteropServices.DllImportAttribute("gdi32.dll")> _
Private Shared Function RealizePalette(ByVal hdc As IntPtr) As Integer
End Function

<System.Security.Permissions.SecurityPermission( _
System.Security.Permissions.SecurityAction.LinkDemand, Flags:= _
System.Security.Permissions.SecurityPermissionFlag.UnmanagedCode)> _
Private Sub GetHalftonePaletteVoid(ByVal e As PaintEventArgs)

    ' Create and draw image.
    Dim imageFile As Image = Image.FromFile("SampImag.jpg")
    e.Graphics.DrawImage(imageFile, New Point(0, 0))

    ' Get handle to device context.
    Dim hdc As IntPtr = e.Graphics.GetHdc()

    ' Get handle to halftone palette.
    Dim htPalette As IntPtr = Graphics.GetHalftonePalette()

    ' Select and realize new palette.
    SelectPalette(hdc, htPalette, True)
    RealizePalette(hdc)

    ' Create new graphics object.
    Dim newGraphics As Graphics = Graphics.FromHdc(hdc)

    ' Draw image with new palette.
    newGraphics.DrawImage(imageFile, 300, 0)

    ' Release handle to device context.
    e.Graphics.ReleaseHdc(hdc)
End Sub

Keterangan

Tujuan dari metode GetHalftonePalette adalah untuk memungkinkan GDI+ menghasilkan halftone kualitas yang lebih baik ketika tampilan menggunakan 8 bit per piksel. Untuk menampilkan gambar menggunakan palet halftone, gunakan prosedur berikut.