How to get a quality value of JPEG image?

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Here is C#/VB.NET code that shows how to get a quality value of JPEG image:

/// <summary>
/// Returns a quality value of JPEG image.
/// </summary>
/// <param name="jpegFilename">A filename of JPEG image.</param>
/// <returns>
/// A quality value of JPEG image.
/// </returns>
public static int GetJpegQuality(string jpegFilename)
{
    // open an existing JPEG file
    using (Vintasoft.Imaging.Codecs.ImageFiles.Jpeg.JpegFile file =
        new Vintasoft.Imaging.Codecs.ImageFiles.Jpeg.JpegFile(
            jpegFilename, System.IO.FileMode.Open, System.IO.FileAccess.Read))
    {
        // return the JPEG quality value
        return file.GetApproximateQualityValue();
    }
}

/// <summary>
/// Returns a quality value of JPEG image.
/// </summary>
/// <param name="image">An image.</param>
/// <returns>
/// A quality value of JPEG image.
/// </returns>
/// <exception cref="System.ArgumentException">Thrown if image does not have JPEG metadata.</exception>
public static int GetJpegQuality(Vintasoft.Imaging.VintasoftImage image)
{
    // get JPEG metadata
    Vintasoft.Imaging.Metadata.JpegMetadata jpegMetadata =
        image.Metadata.MetadataTree as Vintasoft.Imaging.Metadata.JpegMetadata;
    // if metadata is not empty
    if (jpegMetadata != null)
        // return the JPEG quality value
        return jpegMetadata.Quality;

    throw new System.ArgumentException("The image does not have JPEG metadata.");
}

VB.NET

''' <summary>
''' Returns a quality value of JPEG image.
''' </summary>
''' <param name="jpegFilename">A filename of JPEG image.</param>
''' <returns>
''' A quality value of JPEG image.
''' </returns>
Public Shared Function GetJpegQuality(jpegFilename As String) As Integer
    ' open an existing JPEG file
    Using file As New Vintasoft.Imaging.Codecs.ImageFiles.Jpeg.JpegFile(jpegFilename, System.IO.FileMode.Open, System.IO.FileAccess.Read)
        ' return the JPEG quality value
        Return file.GetApproximateQualityValue()
    End Using
End Function

''' <summary>
''' Returns a quality value of JPEG image.
''' </summary>
''' <param name="image">An image.</param>
''' <returns>
''' A quality value of JPEG image.
''' </returns>
''' <exception cref="System.ArgumentException">Thrown if image does not have JPEG metadata.</exception>
Public Shared Function GetJpegQuality(image As Vintasoft.Imaging.VintasoftImage) As Integer
    ' get JPEG metadata
    Dim jpegMetadata As Vintasoft.Imaging.Metadata.JpegMetadata = TryCast(image.Metadata.MetadataTree, Vintasoft.Imaging.Metadata.JpegMetadata)
    ' if metadata is not empty
    If jpegMetadata IsNot Nothing Then
        ' return the JPEG quality value
        Return jpegMetadata.Quality
    End If

    Throw New System.ArgumentException("The image does not have JPEG metadata.")
End Function

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