Best way to draw thumbnails?

This is a discussion on Best way to draw thumbnails? within the C# Programming forums, part of the General Programming Boards category; Hello...I'm trying to speed up the thumbnail loads for a photo app. Is this the best way to draw a ...

  1. #1
    Registered User verbity's Avatar
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    Best way to draw thumbnails?

    Hello...I'm trying to speed up the thumbnail loads for a photo app. Is this the best way to draw a thumbnail? There's about 3 other functions involved but I'm just wondering about this particular one.



    Code:
    private static void PrintImage(object o, PrintPageEventArgs e)
    
            {
    
                var img = new Bitmap(printImagePath);
    
                var p = new Point(10, 10);
    
                e.Graphics.DrawImage(img, p);
    
                img.Dispose(); //dispose of the image!!!!
    
            }


    Thanks for any help.

  2. #2
    Gawking at stupidity
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    That's not really showing a thumbnail...that's just showing the image at a particular location. Shouldn't you have some scaling in there?
    If you understand what you're doing, you're not learning anything.

  3. #3
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    Here is the method I use ( to create a thumbnail from a source image's bytes ):

    Code:
            byte[] GetFileThumbnail(byte[] srcImage, System.Drawing.Imaging.ImageFormat imageFormat)
            {
                 System.IO.MemoryStream ms = new MemoryStream(srcImage);
                System.Drawing.Image image = System.Drawing.Image.FromStream(ms);
                System.Drawing.Image thumbnailImage = image.GetThumbnailImage(64, 64, new System.Drawing.Image.GetThumbnailImageAbort(ThumbnailCallback), IntPtr.Zero);
                
                using (MemoryStream ms2 = new MemoryStream()) 
                { 
                    thumbnailImage.Save(ms2,imageFormat);
                    thumbnailImage.Dispose();
                    image.Dispose();
                    return ms2.ToArray();
                } 
            }
    
    public bool ThumbnailCallback()
            {
                return true;
            }

    Basically you create a thumbnail for each image file using the above method, then draw the thumbnail image using the same method you would draw any image.
    Last edited by Serapth; 11-23-2011 at 03:35 PM. Reason: Add thumbnailCallback()

  4. #4
    Registered User verbity's Avatar
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    Hmmm not sure...lemme check the functions calling it...

  5. #5
    Registered User verbity's Avatar
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    Here's the scaling:

    Code:
                {
                    Image tempImage = Image.FromFile(imageData.Path);
                    //imageData.size = tempImage.Size;
                    //_albumData.setData(imageData, id);
                    imageData.Size.Height = tempImage.Height;
                    imageData.Size.Width = tempImage.Width;
                    newPanel.BackgroundImage = Utilities.ScalImage(tempImage,
                                                                   new Size(_frameSize.Width*thumbNailQuality,
                                                                            _frameSize.Height*thumbNailQuality));
                    //imageData.size = newPanel.BackgroundImage.Size;
                    tempImage.Dispose();
                }

  6. #6
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    The better way is to not use the C# way. It's awfully slow.

    ImageFast: A stand-alone library for quickly loading GDI+ images without validation. - Justin Rogers

    After loading it you can then use this link:

    [C#] Fast Acces To Bitmap Pixels? - C# | Dream.In.Code

    I've used this class wonderfully, including heavy editing and it just blows the C# image handling out of the water.
    He who asks is a fool for five minutes, but he who does not ask remains a fool forever.

    The fool wonders, the wise man asks. - Benjamin Disraeli

    There are no foolish questions and no man becomes a fool until he has stopped asking questions. Charles Steinmetz

  7. #7
    Registered User verbity's Avatar
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    How do you call that thing?

  8. #8
    Registered User
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    Can't properly remember, not at my computer. But use those classes in your project. Then you can use inheritance to expand the individual functionality.

    Code:
    unsafebitmap ub = new ub(imagefast.fromfile(filepath));
    Excuse the type case!

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