Binaryworld - ImageFormatUtils class - Find the ImageFormat for a filename or MIME t ... [ VB.net -> Graphics ]

'/// <summary>
'/// Provides static (Shared) methods to find the
'/// ImageFormat for a filename or MIME type.
'/// </summary>
Public NotInheritable Class ImageFormatUtils
  Private Shared codecs() As ImageCodecInfo
  Private Shared formats As Hashtable

  Shared Sub New()
    '// Get a combined list of all codecs
    Dim encoders() As ImageCodecInfo = ImageCodecInfo.GetImageEncoders()
    If encoders Is Nothing Then ReDim encoders(0)
    Dim decoders() As ImageCodecInfo = ImageCodecInfo.GetImageDecoders()
    If decoders Is Nothing Then ReDim decoders(0)

    Dim codec As ImageCodecInfo
    Dim htCodecs As new Hashtable(encoders.Length + decoders.Length)
    Dim i As Integer

    For i = 0 To encoders.Length - 1
      codec = encoders(i)
      htCodecs.Add(codec.Clsid, codec)
    Next
    For i = 0 To decoders.Length - 1
      codec = decoders(i)
      If Not htCodecs.ContainsKey(codec.Clsid) Then
        htCodecs.Add(codec.Clsid, codec)
      End If
    Next

    ReDim codecs(htCodecs.Count - 1)
    htCodecs.Values.CopyTo(codecs, 0)

    '// Enumerate the pre-defined formats
    Try
      Dim tImageFormat As Type = GetType(ImageFormat)
      Dim props() As PropertyInfo = tImageFormat.GetProperties _
        (BindingFlags.Public Or BindingFlags.Static)
      Dim prop As PropertyInfo
      Dim format As ImageFormat

      formats = new Hashtable(props.Length)
      For i = 0 To props.Length - 1
        prop = props(i)
        If prop.PropertyType Is tImageFormat Then
          format = DirectCast(prop.GetValue(Nothing, Nothing), _
            ImageFormat)
          formats.Add(format.Guid, format)
        End If
      Next
    Catch
    End Try
  End Sub

  '/// <summary>
  '/// Returns the ImageFormat instance for the
  '/// specified format ID. Uses reflection to
  '/// test the static instances of the class
  '/// for the correct ID, before using the
  '/// constructor.
  '/// </summary>
  '/// <param name="formatID">
  '/// The Guid which contains the format ID.
  '/// </param>
  '/// <returns>
  '/// The corresponding ImageFormat object.
  '/// </returns>
  Public Shared Function FromID(ByVal formatID As Guid) As ImageFormat
    If formats Is Nothing OrElse Not formats.ContainsKey(formatID) Then
      Return New ImageFormat(formatID)
    Else
      Return DirectCast(formats(formatID), ImageFormat)
    End If
  End Function

  '/// <summary>
  '/// Returns the ImageCodecInfo which corresponds
  '/// to the specified MIME type.
  '/// </summary>
  '/// <param name="mimeType">
  '/// The MIME type, e.g. "image/jpeg"
  '/// </param>
  '/// <returns>
  '/// The ImageCodecInfo for the MIME type.
  '/// </returns>
  Public Shared Function CodecFromMime(ByVal mimeType As String) As _
    ImageCodecInfo
    If mimeType Is Nothing OrElse 0 = mimeType.Length Then
      Throw New ArgumentNullException("mimeType")
    End If

    Dim i As Integer
    For i = 0 To codecs.Length - 1
      If 0 = String.Compare(codecs(i).MimeType, mimeType, true) Then
        Return codecs(i)
      End If
    Next

    Return Nothing
  End Function

  '/// <summary>
  '/// Returns the ImageFormat which corresponds
  '/// to the specified MIME type.
  '/// </summary>
  '/// <param name="mimeType">
  '/// The MIME type, e.g. "image/jpeg"
  '/// </param>
  '/// <returns>
  '/// The ImageFormat for the MIME type.
  '/// </returns>
  Public Shared Function FromMime(ByVal mimeType As String) As ImageFormat
    If mimeType Is Nothing OrElse 0 = mimeType.Length Then
      Throw New ArgumentNullException("mimeType")
    End If

    Dim info As ImageCodecInfo = CodecFromMime(mimeType)
    If info Is Nothing Then
      Return Nothing
    Else
      Return FromID(info.FormatID)
    End If
  End Function

  '/// <summary>
  '/// Returns an ImageCodecInfo which corresponds
  '/// to the extension of the supplied filename.
  '/// </summary>
  '/// <param name="filename">
  '/// The filename or extension of the image.
  '/// </param>
  '/// <returns>
  '/// The ImageCodecInfo for the filename.
  '/// </returns>
  Public Shared Function CodecFromExtension(ByVal filename As String) As _
    ImageCodecInfo
    If filename Is Nothing OrElse 0 = filename.Length Then
      Throw New ArgumentNullException("filename")
    End If

    Dim index As Integer = filename.LastIndexOf("."c)
    If -1 = index Then Return Nothing

    Dim ext As String = "*." & filename.Substring(index + 1)
    Dim i As Integer
    For i = 0 To codecs.Length - 1
      Dim extensions() As String = codecs(i).FilenameExtension.Split(";"c)
      Dim j As Integer
      For j = 0 To extensions.Length - 1
        If 0 = String.Compare(extensions(j), ext, true) Then
          Return codecs(i)
        End If
      Next
    Next

    Return Nothing
  End Function

  '/// <summary>
  '/// Returns an ImageFormat which corresponds
  '/// to the extension of the supplied filename.
  '/// </summary>
  '/// <param name="filename">
  '/// The filename or extension of the image.
  '/// </param>
  '/// <returns>
  '/// The ImageFormat for the filename.
  '/// </returns>
  Public Shared Function FromExtension(ByVal filename As String) As _
    ImageFormat
    If filename Is Nothing OrElse 0 = filename.Length Then
      Throw New ArgumentNullException("filename")
    End If

    Dim info As ImageCodecInfo = CodecFromExtension(filename)
    If info Is Nothing Then
      Return Nothing
    Else
      Return FromID(info.FormatID)
    End If
  End Function

  '/// <summary>
  '/// No need to create an instance of this class.
  '/// </summary>
  Private Sub New()
  End Sub
End Class

' *******************
' * SAMPLE USAGE
' *******************

Option Explicit
Option Strict

Imports System
Imports System.Collections
Imports System.Reflection
Imports System.Drawing.Imaging

Class App
  Shared Sub Main()
    Try
      Dim file As String
      Dim index As Integer
      Dim codec As ImageCodecInfo

      do
        Console.Write("Enter a file name or MIME type: ")
        file = Console.ReadLine()

        If Not (file Is Nothing) AndAlso 0 < file.Length Then
          index = file.IndexOf("/"c)
          If -1 = index Then
            codec = ImageFormatUtils.CodecFromExtension(file)
          Else
            codec = ImageFormatUtils.CodecFromMime(file)
          End If

          If codec Is Nothing Then
            Console.WriteLine("Unknown format.")
          Else
            WriteCodec(codec)
          End If

          Console.WriteLine()
        End If
      Loop While Not(file Is Nothing) AndAlso 0 < file.Length

    Catch ex As Exception
      Console.WriteLine(ex)
    End Try
  End Sub

  Shared Sub WriteCodec(ByVal codec As ImageCodecInfo)
    If codec Is Nothing Then Throw New ArgumentNullException("codec")

    Console.WriteLine("Format: {0}", ImageFormatUtils.FromID(codec.FormatID) _
      )
    Console.WriteLine("Name: {0}", codec.CodecName)
    Console.WriteLine("DLL: {0}", codec.DllName)
    Console.WriteLine("Version: {0}", codec.Version)
    Console.WriteLine("Extension: {0}", codec.FilenameExtension)
    Console.WriteLine("MIME: {0}", codec.MimeType)
  End Sub
End Class