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8.8

Image.GetThumbnailImage throws System.OutOfMemoryException in some cases.

Asked by Velio in C# Programming Language, .NET Framework 2.x, Visual Studio

Tags: Microsoft, Visual Studio 2005, C#, GDI+

Hi,

Here's some background info: I've got an app which interfaces with a scanner, saves the scanned pages as images in a user-specified format, does some processing on those images and "uploads" them to a remote database via a web-service.

If the processing of any of the images fails, the user is shown a dialog containing thumbnails of all the images, with the erroneous ones highlighted. The user can then choose to "skip" those images, so that they are not uploaded.

The problem occurs sometimes when the thumbnails are generated (inside a UserControl - code included below). If the files are TIFF files, the Image.GetThumbnailImage call (inside the Thumbnail helper class - code also included) throws an OutOfMemoryException, even when there are only a handful (2-5) images. If I change the format of the scanned files to PNG or JPEG, it generates the thumbnails properly.

I wrote a little test app which only uses the Thumbnail class to generate thumbnails. When I run the test app and the main app against the same set of images, the test app generated the thumbnails successfully (on my dev machine) but the main app fell over (on the production machine). Both machines have 2GB of memory but from what I've experienced and found on the web about GDI+, it seems it likes to throw the OutOfMemoryException for a whole range of reasons, not necessarily related to lack of memory.

Any ideas as to the cause and solution would be much appreciated. 
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//USER CONTROL CODE
    public delegate void NoArgDelegate();
    public delegate void ImageArgDelegate(Image image);
 
    public partial class ScannedImageTile : UserControl
    {
        private ScannedFile _scannedFile;
        private Image _image;
        private static Size _thumbSize = new Size(72, 102);
        
        public ScannedImageTile()
        {
            InitializeComponent();
        }
 
        public ScannedFile ScannedFile
        {
            get { return _scannedFile; }
            set { 
                _scannedFile = value;
                if (_scannedFile == null)
                {
                    if (_image != null) _image.Dispose();
                    _image = null;
                    _pictureBox = null;
                }
                else
                {
                    _errorProvider.SetError(_pictureBox, _scannedFile.ErrorMessages);
                }
            }
        }
 
        private void GetThumbnail()
        {
            using (MemoryStream stream = new MemoryStream(_scannedFile.GetImageData()))
            {
                _image = Image.FromStream(stream);
            }
            Image thumb = Thumbnail.GetThumbnailImage(ref _thumbSize, _image);
            UpdatePictureSafely(thumb);
        }
 
        private void UpdatePictureSafely(Image thumb)
        {
            if (this.InvokeRequired)
            {
                this.BeginInvoke(new ImageArgDelegate(UpdatePictureSafely), thumb);
            }
            else
            {
                _pictureBox.Image = thumb;
            }
        }
 
        private void ScannedImageTile_Paint(object sender, PaintEventArgs e)
        {
            if (_scannedFile != null && _pictureBox.Image == null)
                BeginInvoke(new NoArgDelegate(GetThumbnail));  
        }
    }
 
//THUMBNAIL HELPER CLASS CODE
    public class Thumbnail:ObjectModelBase
    {
        ...
        public static System.Drawing.Image GetThumbnailImage(ref Size thumbSize, System.Drawing.Image image)
        {
            System.Drawing.Image.GetThumbnailImageAbort myCallback =
                                  new System.Drawing.Image.GetThumbnailImageAbort(ThumbnailCallback);
 
            System.Drawing.Image thumb = image.GetThumbnailImage(thumbSize.Width, thumbSize.Height, myCallback, IntPtr.Zero);
            return thumb;
        }
 
        private static bool ThumbnailCallback()
        {
            return false;
        }
    }
[+][-]06/23/08 01:08 AM, ID: 21844291Accepted Solution

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About this solution

Zones: C# Programming Language, .NET Framework 2.x, Visual Studio
Tags: Microsoft, Visual Studio 2005, C#, GDI+
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Solution Provided By: Velio
Participating Experts: 2
Solution Grade: A
 
[+][-]06/21/08 04:29 AM, ID: 21837230Assisted Solution

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