GetPageThumbnail(Int32,Int32,GdPictureColor) Method

In This Topic

Creates a custom sized high quality (HQ) thumbnail of the currently selected page of the loaded PDF document. The current page is converted to an image resource with the size and the background color you have specified, which is subsequently stored as an object of the type GdPictureImage. The produced image is in the 32-bit ARGB pixel format. The created image is clearly recognizable by the returned unique image identifier and you can take advantages of the GdPictureImaging class and its methods for further manipulation with the thumbnail.

Syntax

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

'Declaration
 
Public Overloads Function GetPageThumbnail( _
   ByVal Width As Integer, _
   ByVal Height As Integer, _
   ByVal BackColor As GdPictureColor _
) As Integer

public int GetPageThumbnail( 
   int Width,
   int Height,
   GdPictureColor BackColor
)

public function GetPageThumbnail( 
    Width: Integer;
    Height: Integer;
    BackColor: GdPictureColor
): Integer;

public function GetPageThumbnail( 
   Width : int,
   Height : int,
   BackColor : GdPictureColor
) : int;

public: int GetPageThumbnail( 
   int Width,
   int Height,
   GdPictureColor BackColor
)

public:
int GetPageThumbnail( 
   int Width,
   int Height,
   GdPictureColor BackColor
)

Parameters

Width: The required width of the newly created thumbnail image, in pixels.
Height: The required height of the newly created thumbnail image, in pixels.
BackColor: A color object that defines the background color of the thumbnail's margins. The created thumbnail image includes predefined margin on both sides painted with the specified color.

Return Value

A unique image identifier of the GdPictureImage object representing the newly created thumbnail's image resource. The GdPicturePDF.GetStat method can be subsequently used to determine if this method has been successful.

Be aware that you need to release the image after being used, for the suitable method please refer to the Remarks section below.

Remarks

This method is only allowed for use with non-encrypted documents.

It is recommend to use the GdPicturePDF.GetStat method to identify the specific reason for the method's failure, if any instead of checking the returned value.

Likewise just to remind you that you to release the image after being used using either the GdPictureImaging.ReleaseGdPictureImage method or the static GdPictureDocumentUtilities.DisposeImage method.

Example

How to get page thumbnails for all pages of the PDF document.

VB.NET
C#

Dim caption As String = "Example: GetPageThumbnail"
Dim gdpicturePDF As New GdPicturePDF()
Dim gdpictureImaging As New GdPictureImaging()
If gdpicturePDF.LoadFromFile("test.pdf", False) = GdPictureStatus.OK Then
    Dim count As Integer = gdpicturePDF.GetPageCount()
    Dim status As GdPictureStatus = gdpicturePDF.GetStat()
    If status = GdPictureStatus.OK Then
        Dim message As String = ""
        Dim thumb_index As Integer = 0
        Dim filename As String = "thumbnail_page0.png"
        For i As Integer = 1 To count
            status = gdpicturePDF.SelectPage(i)
            If status = GdPictureStatus.OK Then
                thumb_index = gdpicturePDF.GetPageThumbnail(200, 200, 255, 165, 0)
                status = gdpicturePDF.GetStat()
                If status = GdPictureStatus.OK Then
                    filename = filename.Replace((i - 1).ToString(), i.ToString())
                    status = gdpictureImaging.SaveAsPNG(thumb_index, filename)
                    If status = GdPictureStatus.OK Then
                        message = message + "The thumbnail of the page nr." + i.ToString() + " has been successfully saved." + vbCrLf
                    Else
                        message = message + "The SaveAsPNG() method has failed for the page nr." + i.ToString() + " with the status: " + status.ToString() + vbCrLf
                    End If
                    gdpictureImaging.ReleaseGdPictureImage(thumb_index)
                    'Or you can use this one:
                    'GdPictureDocumentUtilities.DisposeImage(thumb_index)
                Else
                    message = message + "The GetPageThumbnail() method has failed for the page nr." + i.ToString() + " with the status: " + status.ToString() + vbCrLf
                End If
            Else
                message = message + "The SelectPage() method has failed for the page nr." + i.ToString() + " with the status: " + status.ToString() + vbCrLf
            End If
        Next
        MessageBox.Show(message, caption)
    Else
        MessageBox.Show("The GetPageCount() method has failed with the status: " + status.ToString(), caption)
    End If
Else
    MessageBox.Show("The file can't be loaded.", caption)
End If
gdpictureImaging.Dispose()
gdpicturePDF.Dispose()

string caption = "Example: GetPageThumbnail";
GdPicturePDF gdpicturePDF = new GdPicturePDF();
GdPictureImaging gdpictureImaging = new GdPictureImaging();
if (gdpicturePDF.LoadFromFile("test.pdf", false) == GdPictureStatus.OK)
{
    int count = gdpicturePDF.GetPageCount();
    GdPictureStatus status = gdpicturePDF.GetStat();
    if (status == GdPictureStatus.OK)
    {
        string message = "";
        int thumb_index = 0;
        string filename = "thumbnail_page0.png";
        for (int i = 1; i <= count; i++)
        {
            status = gdpicturePDF.SelectPage(i);
            if (status == GdPictureStatus.OK)
            {
                thumb_index = gdpicturePDF.GetPageThumbnail(200, 200, 255, 165, 0);
                status = gdpicturePDF.GetStat();
                if (status == GdPictureStatus.OK)
                {
                    filename = filename.Replace((i - 1).ToString(), i.ToString());
                    status = gdpictureImaging.SaveAsPNG(thumb_index, filename);
                    if (status == GdPictureStatus.OK)
                        message = message + "The thumbnail of the page nr." + i.ToString() + " has been successfully saved.\n";
                    else
                        message = message + "The SaveAsPNG() method has failed for the page nr." + i.ToString() + " with the status: " + status.ToString() + "\n";
                    gdpictureImaging.ReleaseGdPictureImage(thumb_index);
                    //Or you can use this one:
                    //GdPictureDocumentUtilities.DisposeImage(thumb_index);
                }
                else
                    message = message + "The GetPageThumbnail() method has failed for the page nr." + i.ToString() + " with the status: " + status.ToString() + "\n";
            }
            else
                message = message + "The SelectPage() method has failed for the page nr." + i.ToString() + " with the status: " + status.ToString() + "\n";
        }
        MessageBox.Show(message, caption);
    }
    else
        MessageBox.Show("The GetPageCount() method has failed with the status: " + status.ToString(), caption);
}
else
    MessageBox.Show("The file can't be loaded.", caption);
gdpictureImaging.Dispose();
gdpicturePDF.Dispose();

Reference

GdPicturePDF Class
GdPicturePDF Members
Overload List
RenderPageToGdPictureImage(Single,Boolean,Double) Method
RenderPageToGdPictureImageEx(Single,Boolean,Double) Method