CODEWITHSUNDEEP
c#.netwpfthumbnails
simo
simo

Reputation: 24558

What's the most efficient way to generate thumbnails?

I am developing a graphical application, and I need to keep a thumbnail for each page. The challenge is how to generate a thumbnail file without loosing performance ??

Currently here is my code to do it:

VisualBrush VisualBrush = new VisualBrush(pageToGenerateThumbnailFor);
UIVisual.Background = VisualBrush;

RenderTargetBitmap = new RenderTargetBitmap((int)UIVisual.ActualWidth, (int)UIVisual.ActualHeight, 96, 96, PixelFormats.Pbgra32);

rtb.Render(UIVisual);

using (FileStream outStream = new FileStream(ThumbFileFullPath, FileMode.OpenOrCreate, 
System.IO.FileAccess.ReadWrite))
{
   PngBitmapEncoder pngEncoder = new PngBitmapEncoder();
   pngEncoder.Frames.Add(BitmapFrame.Create(rtb));
   pngEncoder.Save(outStream);
}

So, Is there a faster way to generate a thumbnail for a given Visual ?

Thanks

Upvotes: 4

Views: 2404

Answers (2)

James
James

Reputation: 936

I did a bit of research recently for generating Image Thumbnails on the fly for an eCommerce site. I started off doing this myself generating a bitmap and then resizing etc. similar to the answer above. After problems with image size on disc and quality I looked in to http://imageresizing.net/ and I haven't looked back since. It can generate images from byte(), streams and physicals files all very quickly with one line of code:

ImageBuilder.Current.Build(New MemoryStream(bImage), sImageLocation + sFullFileName, New      ResizeSettings("maxwidth=214&maxheight=238"))

I would definitely recommend this component rather than trying to reinvent the wheel...

Upvotes: 3

Kevin
Kevin

Reputation: 562

The following class from a utility library that I've written performs well for me and produces good clear quality thumbnails...

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Threading;

namespace Simple {
    public static class ThumbnailCreator {
        private static readonly object _lock = new object();

        public static Bitmap createThumbnail(Stream source, Int32 width, Int32 height) {
            Monitor.Enter(_lock);
            Bitmap output = null;
            try {
                using (Bitmap workingBitmap = new Bitmap(source)) {
                    // Determine scale based on requested height/width (this preserves aspect ratio)
                    Decimal scale;
                    if (((Decimal)workingBitmap.Width / (Decimal)width) > ((Decimal)workingBitmap.Height / (Decimal)height)) {
                        scale = (Decimal)workingBitmap.Width / (Decimal)width;
                    }
                    else {
                        scale = (Decimal)workingBitmap.Height / (Decimal)height;
                    }
                    // Calculate new height/width
                    Int32 newHeight = (Int32)((Decimal)workingBitmap.Height / scale);
                    Int32 newWidth = (Int32)((Decimal)workingBitmap.Width / scale);
                    // Create blank BitMap of appropriate size
                    output = new Bitmap(newWidth, newHeight, PixelFormat.Format32bppArgb);
                    // Create Graphics surface
                    using (Graphics g = Graphics.FromImage(output)) {
                        g.CompositingMode = System.Drawing.Drawing2D.CompositingMode.SourceCopy;
                        g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                        Rectangle destRectangle = new Rectangle(0, 0, newWidth, newHeight);
                        // Use Graphics surface to draw resized BitMap to blank BitMap
                        g.DrawImage(workingBitmap, destRectangle, 0, 0, workingBitmap.Width, workingBitmap.Height, GraphicsUnit.Pixel);
                    }
                }
            }
            catch {
                output = null;
            }
            finally {
                Monitor.Exit(_lock);
            }
            return output;
        }
    }
}

it also retains the original image's aspect ratio.

Upvotes: 1

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