LEADTOOLS Windows Forms (Leadtools.WinForms assembly) Send comments on this topic. | Back to Introduction - All Topics | Help Version 17.0.3.30
LoadThumbnails(IEnumerable<String>,String,RasterThumbnailBrowserLoadFlags) Method
See Also 
Leadtools.WinForms Namespace > RasterThumbnailBrowser Class > LoadThumbnails Method : LoadThumbnails(IEnumerable<String>,String,RasterThumbnailBrowserLoadFlags) Method



paths
The paths to browse. This can be a directories and files.
searchPattern
The search string to match against the names of files in path. The parameter cannot end in two periods ("..") or contain two periods ("..") followed by System.IO.Path.DirectorySeparatorChar or System.IO.Path.AltDirectorySeparatorChar, nor can it contain any of the characters in System.IO.Path.InvalidPathChars.
flags
An RasterThumbnailBrowserLoadFlags enumeration that can be a combination of the following:
Value Description
RasterThumbnailBrowserLoadFlags.None Default mode, the method will return immediatly and the thumbnails are loaded in a background thread.
RasterThumbnailBrowserLoadFlags.Block The method will not return until all thumbnails are loaded.
RasterThumbnailBrowserLoadFlags.OnlyValidImageFiles Only valid image files are loaded. Any file that contains data not recognized by the RasterThumbnailBrowser.Codecs object as a valid image file will not be loaded.
paths
The paths to browse. This can be a directories and files.
searchPattern
The search string to match against the names of files in path. The parameter cannot end in two periods ("..") or contain two periods ("..") followed by System.IO.Path.DirectorySeparatorChar or System.IO.Path.AltDirectorySeparatorChar, nor can it contain any of the characters in System.IO.Path.InvalidPathChars.
flags
An RasterThumbnailBrowserLoadFlags enumeration that can be a combination of the following:
Value Description
RasterThumbnailBrowserLoadFlags.None Default mode, the method will return immediatly and the thumbnails are loaded in a background thread.
RasterThumbnailBrowserLoadFlags.Block The method will not return until all thumbnails are loaded.
RasterThumbnailBrowserLoadFlags.OnlyValidImageFiles Only valid image files are loaded. Any file that contains data not recognized by the RasterThumbnailBrowser.Codecs object as a valid image file will not be loaded.
Browses the specified paths for supported images, and generates thumbnails for each image file that is found.

Syntax

Visual Basic (Declaration) 
Overloads Public Sub LoadThumbnails( _
   ByVal paths As IEnumerable(Of String), _
   ByVal searchPattern As String, _
   ByVal flags As RasterThumbnailBrowserLoadFlags _
) 
Visual Basic (Usage)Copy Code
Dim instance As RasterThumbnailBrowser
Dim paths As IEnumerable(Of String)
Dim searchPattern As String
Dim flags As RasterThumbnailBrowserLoadFlags
 
instance.LoadThumbnails(paths, searchPattern, flags)
C# 
public void LoadThumbnails( 
   IEnumerable<string> paths,
   string searchPattern,
   RasterThumbnailBrowserLoadFlags flags
)
C++/CLI 
public:
void LoadThumbnails( 
   IEnumerable<String^>^ paths,
   String^ searchPattern,
   RasterThumbnailBrowserLoadFlags flags
) 

Parameters

paths
The paths to browse. This can be a directories and files.
searchPattern
The search string to match against the names of files in path. The parameter cannot end in two periods ("..") or contain two periods ("..") followed by System.IO.Path.DirectorySeparatorChar or System.IO.Path.AltDirectorySeparatorChar, nor can it contain any of the characters in System.IO.Path.InvalidPathChars.
flags
An RasterThumbnailBrowserLoadFlags enumeration that can be a combination of the following:
Value Description
RasterThumbnailBrowserLoadFlags.None Default mode, the method will return immediatly and the thumbnails are loaded in a background thread.
RasterThumbnailBrowserLoadFlags.Block The method will not return until all thumbnails are loaded.
RasterThumbnailBrowserLoadFlags.OnlyValidImageFiles Only valid image files are loaded. Any file that contains data not recognized by the RasterThumbnailBrowser.Codecs object as a valid image file will not be loaded.

Example

This example will load two files and expands the multipage one.

Visual BasicCopy Code
Private Class MyForm2 : Inherits Form
      Public theBrowser As RasterThumbnailBrowser
      Public cancelOperation As Boolean ' Informs us if the user canceled the operation
      Public buttonCancel As Button ' Cancel browse loading
      Public buttonBrowse As Button ' Diplays the browse control
      Public progressBar As ProgressBar ' shows progress of loading browse images
      Private Sub buttonBrowse_Click(ByVal sender As Object, ByVal e As EventArgs)
         ' If we are already loading thumbails, cancel
         ' this operation
         If theBrowser.IsLoadingThumbnails Then
            theBrowser.CancelLoadingThumbnails()
         End If

         ' Clean all the items
         theBrowser.Items.Clear()

         ' Update the application state
         buttonCancel.Enabled = True
         progressBar.Value = 0

         ' And load the new thumbnails
         cancelOperation = False

         Dim folderPath As String = LEAD_VARS.ImagesDir
         Dim files As String() = New String(1) {Path.Combine(folderPath, "\image1.jpx"), folderPath}
         theBrowser.LoadThumbnails(files, "*.jpg", RasterThumbnailBrowserLoadFlags.Block Or RasterThumbnailBrowserLoadFlags.ExpandMultiPageFile)
      End Sub

      Private Sub thumbnailBrowser_LoadThumbnail(ByVal sender As Object, ByVal e As RasterThumbnailBrowserLoadThumbnailEventArgs)
         ' If this is the first iteration, update the progress bar minimum and maximum values
         If e.Index = 0 Then
            progressBar.Minimum = 0
            progressBar.Maximum = e.Total - 1
         End If

         ' Update where we are in the loading operation
         progressBar.Value = e.Index

         ' Check if we need to cancel (due to the user clicking the Cancel button)
         If cancelOperation Then
            e.Cancel = True
         End If
      End Sub

      Private Sub thumbnailBrowser_AddFile(ByVal sender As Object, ByVal e As RasterThumbnailBrowserAddFileEventArgs)
         Console.WriteLine("AddFile: {0}    Add: {1} Total Pages: {2} Page:{3}", e.FileName, e.Add, e.TotalPages, e.Page)
      End Sub

      Private Sub thumbnailBrowser_FinishedLoadingThumbnails(ByVal sender As Object, ByVal e As EventArgs)
         buttonCancel.Enabled = False
      End Sub

      Private Sub buttonCancel_Click(ByVal sender As Object, ByVal e As EventArgs)
         ' The user has clicked the cancel button
         Me.cancelOperation = True
      End Sub

      ' Create  custom images to use as the "error" and "loading" thumbnails.
      Private Sub CreateErrorThumbnail()
         ' Get the image size
         Dim imageSize As Size = theBrowser.ItemImageSize

         ' No "loading" thumbnail
         theBrowser.LoadingThumbnail = Nothing

         ' For the "error" thumbnail, create a red X image
         Dim palette As RasterColor() = New RasterColor() {}
         Dim image As RasterImage = New RasterImage(RasterMemoryFlags.Conventional, imageSize.Width, imageSize.Height, 24, RasterByteOrder.Bgr, RasterViewPerspective.TopLeft, palette, IntPtr.Zero, 0)

         Dim hdc As IntPtr = RasterImagePainter.CreateLeadDC(image)
         Dim g As Graphics = Graphics.FromHdc(hdc)

         g.FillRectangle(Brushes.Magenta, 0, 0, imageSize.Width, imageSize.Height)

         g.DrawLine(Pens.Red, 0, 0, imageSize.Width, imageSize.Height)
         g.DrawLine(Pens.Red, imageSize.Width, 0, 0, imageSize.Height)

         g.Dispose()
         RasterImagePainter.DeleteLeadDC(hdc)

         ' Make this image transparent
         image.Transparent = True
         image.TransparentColor = RasterColor.FromKnownColor(RasterKnownColor.Magenta)

         theBrowser.ErrorThumbnail = image
      End Sub

      Public Sub Cleanup()
         RemoveHandler buttonBrowse.Click, AddressOf buttonBrowse_Click
         RemoveHandler buttonCancel.Click, AddressOf buttonCancel_Click
         RemoveHandler theBrowser.LoadThumbnail, AddressOf thumbnailBrowser_LoadThumbnail
         RemoveHandler theBrowser.FinishedLoadingThumbnails, AddressOf thumbnailBrowser_FinishedLoadingThumbnails
      End Sub

      Public Sub New()
         Size = New Size(300, 200)

         ' create the browser
         theBrowser = New RasterThumbnailBrowser()
         theBrowser.Codecs = New RasterCodecs()
         theBrowser.Dock = DockStyle.Fill
         theBrowser.ItemSpacingSize = New Size(10, 10)
         theBrowser.ThumbnailSizeFlags = RasterSizeFlags.Bicubic
         AddHandler theBrowser.LoadThumbnail, AddressOf thumbnailBrowser_LoadThumbnail
         AddHandler theBrowser.FinishedLoadingThumbnails, AddressOf thumbnailBrowser_FinishedLoadingThumbnails
         AddHandler theBrowser.AddFile, AddressOf thumbnailBrowser_AddFile

         ' Create a thumbnail image to be displayed on error
         CreateErrorThumbnail()

         ' add a panel
         Dim panel As Panel = New Panel()
         panel.Dock = DockStyle.Left
         panel.Width = 100
         Controls.Add(panel)
         panel.BringToFront()

         ' add a "browse" button
         buttonBrowse = New Button()
         buttonBrowse.Text = "Browse"
         buttonBrowse.Dock = DockStyle.Top
         panel.Controls.Add(buttonBrowse)
         AddHandler buttonBrowse.Click, AddressOf buttonBrowse_Click

         ' add a "cancel" button
         buttonCancel = New Button()
         buttonCancel.Text = "Cancel"
         buttonBrowse.Dock = DockStyle.Bottom
         panel.Controls.Add(buttonCancel)
         AddHandler buttonCancel.Click, AddressOf buttonCancel_Click

         ' add a progress bar
         progressBar = New ProgressBar()
         progressBar.Dock = DockStyle.Bottom
         Controls.Add(progressBar)

         Controls.Add(theBrowser)
         theBrowser.BringToFront()
      End Sub

      Private Sub InitializeComponent()
         Me.SuspendLayout()
         ' 
         ' MyForm
         ' 
         Me.ClientSize = New System.Drawing.Size(315, 273)
         Me.Name = "MyForm"
         Me.ResumeLayout(False)

      End Sub
   End Class
   Public Sub RasterThumbnailBrowser_RasterThumbnailBrowser()
      Dim form As MyForm = New MyForm()
      form.ShowDialog()
      form.Cleanup()
   End Sub

Public NotInheritable Class LEAD_VARS
   Public Const ImagesDir As String = "C:\Users\Public\Documents\LEADTOOLS Images"
End Class
C#Copy Code
class MyForm2 : Form
   {
      public RasterThumbnailBrowser theBrowser;
      public bool cancelOperation;        // Informs us if the user canceled the operation
      public Button buttonCancel;         // Cancel browse loading
      public Button buttonBrowse;         // Diplays the browse control
      public ProgressBar progressBar;     // shows progress of loading browse images
      void buttonBrowse_Click(object sender, EventArgs e)
      {
         // If we are already loading thumbails, cancel
         // this operation
         if (theBrowser.IsLoadingThumbnails)
            theBrowser.CancelLoadingThumbnails();

         // Clean all the items
         theBrowser.Items.Clear();

         // Update the application state
         buttonCancel.Enabled = true;
         progressBar.Value = 0;

         // And load the new thumbnails
         cancelOperation = false;

         string folderPath = LEAD_VARS.ImagesDir;
         string[] files = new string[2] { Path.Combine(folderPath , "\\image1.jpx"), folderPath };
         theBrowser.LoadThumbnails(files, "*.jpg", RasterThumbnailBrowserLoadFlags.Block | RasterThumbnailBrowserLoadFlags.ExpandMultiPageFile);
      }

      private void thumbnailBrowser_LoadThumbnail(object sender, RasterThumbnailBrowserLoadThumbnailEventArgs e)
      {
         // If this is the first iteration, update the progress bar minimum and maximum values
         if (e.Index == 0)
         {
            progressBar.Minimum = 0;
            progressBar.Maximum = e.Total - 1;
         }

         // Update where we are in the loading operation
         progressBar.Value = e.Index;

         // Check if we need to cancel (due to the user clicking the Cancel button)
         if (cancelOperation)
            e.Cancel = true;
      }

      private void thumbnailBrowser_AddFile(object sender, RasterThumbnailBrowserAddFileEventArgs e)
      {
         Console.WriteLine("AddFile: {0}    Add: {1} Total Pages : {2} Page : {3}", e.FileName, e.Add, e.TotalPages, e.Page);
      }

      private void thumbnailBrowser_FinishedLoadingThumbnails(object sender, EventArgs e)
      {
         buttonCancel.Enabled = false;
      }

      private void buttonCancel_Click(object sender, EventArgs e)
      {
         // The user has clicked the cancel button
         this.cancelOperation = true;
      }

      // Create  custom images to use as the "error" and "loading" thumbnails.
      void CreateErrorThumbnail()
      {
         // Get the image size
         Size imageSize = theBrowser.ItemImageSize;

         // No "loading" thumbnail
         theBrowser.LoadingThumbnail = null;

         // For the "error" thumbnail, create a red X image
         RasterColor[] palette = new RasterColor[0];
         RasterImage image = new RasterImage(
            RasterMemoryFlags.Conventional,
            imageSize.Width,
            imageSize.Height,
            24,
            RasterByteOrder.Bgr,
            RasterViewPerspective.TopLeft,
         palette,
         IntPtr.Zero,
         0
         );

         IntPtr hdc = RasterImagePainter.CreateLeadDC(image);
         Graphics g = Graphics.FromHdc(hdc);

         g.FillRectangle(Brushes.Magenta, 0, 0, imageSize.Width, imageSize.Height);

         g.DrawLine(Pens.Red, 0, 0, imageSize.Width, imageSize.Height);
         g.DrawLine(Pens.Red, imageSize.Width, 0, 0, imageSize.Height);

         g.Dispose();
         RasterImagePainter.DeleteLeadDC(hdc);

         // Make this image transparent
         image.Transparent = true;
         image.TransparentColor = RasterColor.FromKnownColor(RasterKnownColor.Magenta);

         theBrowser.ErrorThumbnail = image;
      }

      public void Cleanup()
      {
         buttonBrowse.Click -= new EventHandler(buttonBrowse_Click);
         buttonCancel.Click -= new EventHandler(buttonCancel_Click);
         theBrowser.LoadThumbnail -= new EventHandler<RasterThumbnailBrowserLoadThumbnailEventArgs>(thumbnailBrowser_LoadThumbnail);
         theBrowser.FinishedLoadingThumbnails -= new EventHandler(thumbnailBrowser_FinishedLoadingThumbnails);
      }

      public MyForm2()
      {
         Size = new Size(300, 200);

         // create the browser
         theBrowser = new RasterThumbnailBrowser();
         theBrowser.Codecs = new RasterCodecs();
         theBrowser.Dock = DockStyle.Fill;
         theBrowser.ItemSpacingSize = new Size(10, 10);
         theBrowser.ThumbnailSizeFlags = RasterSizeFlags.Bicubic;
         theBrowser.LoadThumbnail += new EventHandler<RasterThumbnailBrowserLoadThumbnailEventArgs>(thumbnailBrowser_LoadThumbnail);
         theBrowser.FinishedLoadingThumbnails += new EventHandler(thumbnailBrowser_FinishedLoadingThumbnails);
         theBrowser.AddFile += new EventHandler<RasterThumbnailBrowserAddFileEventArgs>(thumbnailBrowser_AddFile);

         // Create a thumbnail image to be displayed on error
         CreateErrorThumbnail();

         // add a panel
         Panel panel = new Panel();
         panel.Dock = DockStyle.Left;
         panel.Width = 100;
         Controls.Add(panel);
         panel.BringToFront();

         // add a "browse" button
         buttonBrowse = new Button();
         buttonBrowse.Text = "Browse";
         buttonBrowse.Dock = DockStyle.Top;
         panel.Controls.Add(buttonBrowse);
         buttonBrowse.Click += new EventHandler(buttonBrowse_Click);

         // add a "cancel" button
         buttonCancel = new Button();
         buttonCancel.Text = "Cancel";
         buttonBrowse.Dock = DockStyle.Bottom;
         panel.Controls.Add(buttonCancel);
         buttonCancel.Click += new EventHandler(buttonCancel_Click);

         // add a progress bar
         progressBar = new ProgressBar();
         progressBar.Dock = DockStyle.Bottom;
         Controls.Add(progressBar);

         Controls.Add(theBrowser);
         theBrowser.BringToFront();
      }

      private void InitializeComponent()
      {
         this.SuspendLayout();
         // 
         // MyForm
         // 
         this.ClientSize = new System.Drawing.Size(315, 273);
         this.Name = "MyForm";
         this.ResumeLayout(false);

      }
   }

   public void RasterThumbnailBrowser_LoadThumbnails2()
   {
      MyForm form = new MyForm();
      form.ShowDialog();
      form.Cleanup();
   }

static class LEAD_VARS
{
   public const string ImagesDir = @"C:\Users\Public\Documents\LEADTOOLS Images";
}

Remarks

Use the RasterThumbnailBrowser.LoadThumbnails method to populate the RasterThumbnailBrowser control with the thumbnails of image files found in the directory specified by path. The control will load the images in the following manner:

Requirements

Target Platforms: Microsoft .NET Framework 2.0, Windows 2000, Windows XP, Windows Server 2003 family, Windows Server 2008 family, Windows Vista, Windows 7

See Also