Encoder.Quality Field

Definition

Namespace:

System.Drawing.Imaging

Assembly:

System.Drawing.Common.dll

Gets an Encoder object that is initialized with the globally unique identifier for the quality parameter category.

public: static initonly System::Drawing::Imaging::Encoder ^ Quality;

public static readonly System.Drawing.Imaging.Encoder Quality;

 staticval mutable Quality : System.Drawing.Imaging.Encoder

Public Shared ReadOnly Quality As Encoder 

Field Value

Encoder

Examples

The following example creates a Bitmap object from a BMP file. The code saves the bitmap to three JPEG files, each with a different quality level.

#using <System.Drawing.dll>

using namespace System;
using namespace System::Drawing;
using namespace System::Drawing::Imaging;
static ImageCodecInfo^ GetEncoderInfo( ImageFormat^ format );
int main()
{
   Bitmap^ myBitmap;
   ImageCodecInfo^ myImageCodecInfo;
   Encoder^ myEncoder;
   EncoderParameter^ myEncoderParameter;
   EncoderParameters^ myEncoderParameters;
   
   // Create a Bitmap object based on a BMP file.
   myBitmap = gcnew Bitmap( "Shapes.bmp" );
   
   // Get an ImageCodecInfo object that represents the JPEG codec.
   myImageCodecInfo = GetEncoderInfo( ImageFormat->Jpeg );
   
   // Create an Encoder object based on the GUID
   // for the Quality parameter category.
   myEncoder = Encoder::Quality;
   
   // Create an EncoderParameters object.
   // An EncoderParameters object has an array of EncoderParameter
   // objects. In this case, there is only one
   // EncoderParameter object in the array.
   myEncoderParameters = gcnew EncoderParameters( 1 );
   
   // Save the bitmap as a JPEG file with quality level 25.
   myEncoderParameter = gcnew EncoderParameter( myEncoder,__int64(25) );
   myEncoderParameters->Param[ 0 ] = myEncoderParameter;
   myBitmap->Save( "Shapes025.jpg", myImageCodecInfo, myEncoderParameters );
   
   // Save the bitmap as a JPEG file with quality level 50.
   myEncoderParameter = gcnew EncoderParameter( myEncoder,__int64(50) );
   myEncoderParameters->Param[ 0 ] = myEncoderParameter;
   myBitmap->Save( "Shapes050.jpg", myImageCodecInfo, myEncoderParameters );
   
   // Save the bitmap as a JPEG file with quality level 75.
   myEncoderParameter = gcnew EncoderParameter( myEncoder,__int64(75) );
   myEncoderParameters->Param[ 0 ] = myEncoderParameter;
   myBitmap->Save( "Shapes075.jpg", myImageCodecInfo, myEncoderParameters );
}

static ImageCodecInfo^ GetEncoderInfo( ImageFormat^ format )
{
   int j;
   array<ImageCodecInfo^>^encoders;
   encoders = ImageCodecInfo::GetImageEncoders();
   for ( j = 0; j < encoders->Length; ++j )
   {
      if ( encoders[ j ]->FormatID == format->Guid)
            return encoders[ j ];

   }
   return nullptr;
}

using System;
using System.Drawing;
using System.Drawing.Imaging;
class Example_SetJPEGQuality
{
    public static void Main()
    {
        Bitmap myBitmap;
        ImageCodecInfo myImageCodecInfo;
        Encoder myEncoder;
        EncoderParameter myEncoderParameter;
        EncoderParameters myEncoderParameters;
                     
        // Create a Bitmap object based on a BMP file.
        myBitmap = new Bitmap("Shapes.bmp");
                     
        // Get an ImageCodecInfo object that represents the JPEG codec.
        myImageCodecInfo = GetEncoderInfo("image/jpeg");
                     
        // Create an Encoder object based on the GUID
                     
        // for the Quality parameter category.
        myEncoder = Encoder.Quality;
                     
        // Create an EncoderParameters object.
                     
        // An EncoderParameters object has an array of EncoderParameter
                     
        // objects. In this case, there is only one
                     
        // EncoderParameter object in the array.
        myEncoderParameters = new EncoderParameters(1);
                     
        // Save the bitmap as a JPEG file with quality level 25.
        myEncoderParameter = new EncoderParameter(myEncoder, 25L);
        myEncoderParameters.Param[0] = myEncoderParameter;
        myBitmap.Save("Shapes025.jpg", myImageCodecInfo, myEncoderParameters);
                     
        // Save the bitmap as a JPEG file with quality level 50.
        myEncoderParameter = new EncoderParameter(myEncoder, 50L);
        myEncoderParameters.Param[0] = myEncoderParameter;
        myBitmap.Save("Shapes050.jpg", myImageCodecInfo, myEncoderParameters);
                     
        // Save the bitmap as a JPEG file with quality level 75.
        myEncoderParameter = new EncoderParameter(myEncoder, 75L);
        myEncoderParameters.Param[0] = myEncoderParameter;
        myBitmap.Save("Shapes075.jpg", myImageCodecInfo, myEncoderParameters);
    }
    private static ImageCodecInfo GetEncoderInfo(String mimeType)
    {
        int j;
        ImageCodecInfo[] encoders;
        encoders = ImageCodecInfo.GetImageEncoders();
        for(j = 0; j < encoders.Length; ++j)
        {
            if(encoders[j].MimeType == mimeType)
                return encoders[j];
        }
        return null;
    }
}

Imports System.Drawing
Imports System.Drawing.Imaging


Class Example_SetJPEGQuality

    Public Shared Sub Main()
        Dim myBitmap As Bitmap
        Dim myImageCodecInfo As ImageCodecInfo
        Dim myEncoder As Encoder
        Dim myEncoderParameter As EncoderParameter
        Dim myEncoderParameters As EncoderParameters

        ' Create a Bitmap object based on a BMP file.
        myBitmap = New Bitmap("Shapes.bmp")

        ' Get an ImageCodecInfo object that represents the JPEG codec.
        myImageCodecInfo = GetEncoderInfo(ImageFormat.Jpeg)

        ' Create an Encoder object based on the GUID
        ' for the Quality parameter category.
        myEncoder = Encoder.Quality

        ' Create an EncoderParameters object.
        ' An EncoderParameters object has an array of EncoderParameter
        ' objects. In this case, there is only one
        ' EncoderParameter object in the array.
        myEncoderParameters = New EncoderParameters(1)

        ' Save the bitmap as a JPEG file with quality level 25.
        myEncoderParameter = New EncoderParameter(myEncoder, CType(25L, Int32))
        myEncoderParameters.Param(0) = myEncoderParameter
        myBitmap.Save("Shapes025.jpg", myImageCodecInfo, myEncoderParameters)

        ' Save the bitmap as a JPEG file with quality level 50.
        myEncoderParameter = New EncoderParameter(myEncoder, CType(50L, Int32))
        myEncoderParameters.Param(0) = myEncoderParameter
        myBitmap.Save("Shapes050.jpg", myImageCodecInfo, myEncoderParameters)

        ' Save the bitmap as a JPEG file with quality level 75.
        myEncoderParameter = New EncoderParameter(myEncoder, CType(75L, Int32))
        myEncoderParameters.Param(0) = myEncoderParameter
        myBitmap.Save("Shapes075.jpg", myImageCodecInfo, myEncoderParameters)

    End Sub

    Private Shared Function GetEncoderInfo(ByVal format As ImageFormat) As ImageCodecInfo
        Dim j As Integer
        Dim encoders() As ImageCodecInfo
        encoders = ImageCodecInfo.GetImageEncoders()

        j = 0
        While j < encoders.Length
            If encoders(j).FormatID = format.Guid Then
                Return encoders(j)
            End If
            j += 1
        End While
        Return Nothing

    End Function 'GetEncoderInfo
End Class

Remarks

The Quality category specifies the level of compression for an image. When used to construct an EncoderParameter, the range of useful values for the quality category is from 0 to 100. The lower the number specified, the higher the compression and therefore the lower the quality of the image. Zero would give you the lowest quality image and 100 the highest.

When you pass a parameter to an image encoder, the parameter is encapsulated in an EncoderParameter object. One of the fields of the EncoderParameter object is a GUID that specifies the category of the parameter. Use the static fields of the Encoder class to retrieve an Encoder that contains parameters of the desired category.

The image encoders that are built into GDI+ receive parameters that belong to several categories. The following table lists all the categories and the GUID associated with each category.

ChrominanceTable f2e455dc-09b3-4316-8260-676ada32481c

ColorDepth 66087055-ad66-4c7c-9a18-38a2310b8337

Compression e09d739d-ccd4-44ee-8eba-3fbf8be4fc58

LuminanceTable edb33bce-0266-4a77-b904-27216099e717

Quality 1d5be4b5-fa4a-452d-9cdd-5db35105e7eb

RenderMethod 6d42c53a-229a-4825-8bb7-5c99e2b9a8b8

SaveFlag 292266fc-ac40-47bf-8cfc-a85b89a655de

ScanMethod 3a4e2661-3109-4e56-8536-42c156e7dcfa

Transformation 8d0eb2d1-a58e-4ea8-aa14-108074b7b6f9

Version 24d18c76-814a-41a4-bf53-1c219cccf797

See also

• Using Image Encoders and Decoders in Managed GDI+