GetDocumentPreview(Stream,String,Int32,Int32,Int32,DocumentFormat,Int32,Int32) Method

In This Topic

Retrieves the format of a required document, the total number of pages of that document and produces the thumbnail of its first page according to the specified parameters. The required document is accessible from a previously instantiated Stream object.

Syntax

Visual Basic
C#
Delphi
JScript
Managed Extensions for C++
C++/CLI

'Declaration
 
Public Overloads Shared Function GetDocumentPreview( _
   ByVal FileStream As Stream, _
   ByVal FileName As String, _
   ByVal ThumbnailWidth As Integer, _
   ByVal ThumbnailHeight As Integer, _
   ByVal BackColor As Integer, _
   ByRef DocumentFormat As DocumentFormat, _
   ByRef ThumbnailID As Integer, _
   ByRef PageCount As Integer _
) As GdPictureStatus

public static GdPictureStatus GetDocumentPreview( 
   Stream FileStream,
   string FileName,
   int ThumbnailWidth,
   int ThumbnailHeight,
   int BackColor,
   ref DocumentFormat DocumentFormat,
   ref int ThumbnailID,
   ref int PageCount
)

public function GetDocumentPreview( 
    FileStream: Stream;
    FileName: String;
    ThumbnailWidth: Integer;
    ThumbnailHeight: Integer;
    BackColor: Integer;
   var  DocumentFormat: DocumentFormat;
   var  ThumbnailID: Integer;
   var  PageCount: Integer
): GdPictureStatus; static;

public static function GetDocumentPreview( 
   FileStream : Stream,
   FileName : String,
   ThumbnailWidth : int,
   ThumbnailHeight : int,
   BackColor : int,
   DocumentFormat : DocumentFormat,
   ThumbnailID : int,
   PageCount : int
) : GdPictureStatus;

public: static GdPictureStatus GetDocumentPreview( 
   Stream* FileStream,
   string* FileName,
   int ThumbnailWidth,
   int ThumbnailHeight,
   int BackColor,
   ref DocumentFormat DocumentFormat,
   ref int ThumbnailID,
   ref int PageCount
)

public:
static GdPictureStatus GetDocumentPreview( 
   Stream^ FileStream,
   String^ FileName,
   int ThumbnailWidth,
   int ThumbnailHeight,
   int BackColor,
   DocumentFormat% DocumentFormat,
   int% ThumbnailID,
   int% PageCount
)

Parameters

FileStream: A System.IO.Stream object. This stream object must be initialized before it can be sent into this method and it should remain open for subsequent use. At the same, the provided stream object must support seeking, otherwise the method will fail.
FileName: The name of the original file. It can be an empty string. Providing this parameter can help the format detection algorithm to distinguish format using the same signature pattern.
ThumbnailWidth: The required width of the generated thumbnail of the first page, in pixels.
ThumbnailHeight: The required height of the generated thumbnail of the first page, in pixels.
BackColor: The required background color of the generated thumbnail, in ARGB format.
DocumentFormat: Output parameter. A member of the DocumentFormat enumeration. The format of the specified document.
ThumbnailID: Output parameter. The unique image identifier of a newly generated thumbnail image of the first page of the specified document. Be aware that you need to subsequently release this image from memory using the DisposeImage method after you have used it.
PageCount: Output parameter. The total number of pages of the specified document.

Return Value

A member of the GdPictureStatus enumeration. If the method has been successfully followed, then the return value is GdPictureStatus.OK.

We strongly recommend always checking this status first.

Remarks

This method is based on the GetDocumentFormat(Stream,String) method when processing the specified stream.

Be aware that the specified stream should remain open during running this method and it needs to be closed by the user as well. At the same, the provided stream must support seeking, otherwise the method will fail.

Likewise, you need to release the thumbnail's image resource from memory using the DisposeImage method.

This method requires the Image Conversion component to run.

Example

How to retrieve extended information of an image file stored within a stream.

VB.NET
C#

Using fileStream As FileStream = New FileStream("input.tif", FileMode.Open)
    Dim documentFormat As GdPicture14.DocumentFormat = GdPicture14.DocumentFormat.DocumentFormatUNKNOWN
    Dim thumbID As Integer = 0, pagesCount As Integer = 0
    Dim status As GdPictureStatus = GdPictureDocumentUtilities.GetDocumentPreview(fileStream, "input.tif", 100, 150, (Color.Aqua).ToArgb(), documentFormat, thumbID, pagesCount)
    If status = GdPictureStatus.OK Then
        MessageBox.Show("Document Preview: " + vbCrLf + "  format: " + GdPicture14.DocumentFormat.ToString() + vbCrLf + "  number of pages: " + pagesCount.ToString(), "GdPicture")
    Else
        MessageBox.Show("Error: " + status.ToString(), "GdPicture")
    End If
    'Do your stuff with thumbID here.
    GdPictureDocumentUtilities.DisposeImage(thumbID)
End Using

using (FileStream fileStream = new FileStream("input.tif", FileMode.Open))
{
    GdPicture14.DocumentFormat documentFormat = GdPicture14.DocumentFormat.DocumentFormatUNKNOWN;
    int thumbID = 0, pagesCount = 0;
    GdPictureStatus status = GdPictureDocumentUtilities.GetDocumentPreview(fileStream, "input.tif", 100, 150, (Color.Aqua).ToArgb(), ref documentFormat, ref thumbID, ref pagesCount);
    if (status == GdPictureStatus.OK)
        MessageBox.Show("Document Preview: \n  format: " + GdPicture14.DocumentFormat.ToString() + "\n  number of pages: " + pagesCount.ToString(), "GdPicture");
    else
        MessageBox.Show("Error: " + status.ToString(), "GdPicture");
    //Do your stuff with thumbID here.
    GdPictureDocumentUtilities.DisposeImage(thumbID);
}

Reference

GdPictureDocumentUtilities Class
GdPictureDocumentUtilities Members
Overload List
DisposeImage Method