Viewing Thumbnails

Update for Vault 2012:  Additional image formats supported. This post applies to Vault 2011 and earlier. Go here for the Vault 2012 code.

Here is how you view thumbnail data from Vault.

Background:
Thumbnails are stored as metafiles, which must be rendered to a display context.  This is a bit different from a jpeg because metafiles have no fixed size.  This is nice because the image can be scaled to any size without loss of detail.

Sample Code:
Once you have found the PropInst object with the thumbnail value, here is how you can render it to a System.Drawing.Image object.

C#:

 

/// <summary> /// Takes a thumbnail property from Vault and renders it to an Image /// </summary> private System.Drawing.Image RenderThumbnailToImage(Document.PropInst propInst, int width, int height) {     // convert the property value to a byte array     byte[] thumbnailRaw = (byte[])propInst.Val;     // load the data into a stream but skip the first 12 bytes     Stream stream = new MemoryStream(thumbnailRaw, 12, thumbnailRaw.Length - 12);     // create the Metafile object     System.Drawing.Imaging.Metafile metafile = new System.Drawing.Imaging.Metafile(stream);     // render the Metafile to an Image object and display in the picture box     Image retVal = metafile.GetThumbnailImage(width, height, new Image.GetThumbnailImageAbort(GetThumbnailImageAbort), IntPtr.Zero);     stream.Close();      return retVal; } /// <summary> /// Delagate for the GetThumnailImage function. /// </summary> private static bool GetThumbnailImageAbort() {     return false;  // do nothing }

VB.NET:

 

''' <summary> ''' Takes a thumbnail property from Vault and renders it to an Image ''' </summary> Private Function RenderThumbnailToImage(ByVal propInst As Document.PropInst, ByVal width As Integer, ByVal height As Integer) As System.Drawing.Image     ' convert the property value to a byte array     Dim thumbnailRaw As Byte() = CType(propInst.Val, Byte())     ' load the data into a stream but skip the first 12 bytes     Dim stream As System.IO.Stream = New System.IO.MemoryStream(thumbnailRaw, 12, thumbnailRaw.Length - 12)     ' create the Metafile object     Dim metafile As System.Drawing.Imaging.Metafile = New System.Drawing.Imaging.Metafile(stream)     ' render the Metafile to an Image object and display in the picture box     Dim retVal As Image = metafile.GetThumbnailImage(width, height, New Image.GetThumbnailImageAbort(AddressOf GetThumbnailImageAbort), IntPtr.Zero)     stream.Close()      Return retVal End Function ''' <summary> ''' Delagate for the GetThumnailImage function. ''' </summary> Private Shared Function GetThumbnailImageAbort() As Boolean      Return False  ' do nothing End Function