CreateThumbnailHQ(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 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 CreateThumbnailHQ( _

   ByVal Width As Integer, _

   ByVal Height As Integer, _

   ByVal BackColor As GdPictureColor _

) As Integer

public int CreateThumbnailHQ( 

   int Width,

   int Height,

   GdPictureColor BackColor

)

public function CreateThumbnailHQ( 

    Width: Integer;

    Height: Integer;

    BackColor: GdPictureColor

): Integer;

public function CreateThumbnailHQ( 

   Width : int,

   Height : int,

   BackColor : GdPictureColor

) : int;

public: int CreateThumbnailHQ( 

   int Width,

   int Height,

   GdPictureColor BackColor

)

public:

int CreateThumbnailHQ( 

   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, that is painted with the specified color.

Return Value

A unique image identifier of the GdPictureImage object representing the newly created thumbnail's image resource. The returned value is non-zero if the image is successfully created. Please first of all use the GdPicturePDF.GetStat method 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 need to release the image after being used using either the GdPictureImaging.ReleaseGdPictureImage method or the static GdPictureDocumentUtilities.DisposeImage method.

This method requires the Annotations component to run.

Example

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

VB.NET
C#

Dim caption As String = "Example: CreateThumbnailHQ"

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.CreateThumbnailHQ(300, 300, Color.Orange)

                status = gdpicturePDF.GetStat()

                If (status = GdPictureStatus.OK) AndAlso (thumb_index <> 0) 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 CreateThumbnailHQ() 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: CreateThumbnailHQ";

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.CreateThumbnailHQ(300, 300, Color.Orange);

                status = gdpicturePDF.GetStat();

                if ((status == GdPictureStatus.OK) && (thumb_index != 0))

                {

                    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 CreateThumbnailHQ() 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
GetPageThumbnail(Int32,Int32,GdPictureColor) Method
RenderPageToGdPictureImage(Single,Boolean,Double) Method