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POProcessing large bitmap images in WPF
 

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  1. POProcessing large bitmap images in WPF
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    <p>I need to process (change brightness, contrast etc) very large high-quality bitmaps (often over 10MPx) several times per second and need to update it on screen every time ( on Image control in WPF). Currently I'm using AForge.NET library for unmanaged image processing, but there are some problems I cannot solve. First of all, one operation takes ~300ms (without updating the screen) which is not acceptable for me. Here's sample code:</p> <pre><code>UnmanagedImage _img; BrightnessCorrection _brightness = new BrightnessCorrection(); void Load() { _img = UnmanagedImage.FromManagedImage((Bitmap)Bitmap.FromFile("image.jpg")); } void ChangeBrightness(int val) // this method is invoked by changing Slider value - several times per second { _brightness.AdjustValue = val; _brightness.ApplyInPlace(_img); // it takes ~300ms for image 22MPx, no screen update - just change brightness "in background" } </code></pre> <p>I have no experience in image processing, but I think it cannot be much faster since it is very high resolution. Am I right?</p> <p>Another problem - how to efficiently update the screen? At the moment I have the following (ofc very bad) solution:</p> <pre><code>void ChangeBrightness(int val) { _brightness.AdjustValue = val; _brightness.ApplyInPlace(_img); using (MemoryStream ms = new MemoryStream()) { using (Bitmap b = _img.ToManagedImage()) { b.Save(ms, ImageFormat.Bmp); ms.Seek(0, SeekOrigin.Begin); var bmp = new BitmapImage(); bmp.BeginInit(); bmp.StreamSource = ms; bmp.CacheOption = BitmapCacheOption.OnLoad; bmp.EndInit(); MyImageControl.Source = new WriteableBitmap(bmp); // !!! } } } </code></pre> <p>As you can see, every time new WriteableBitmap is created (you can imagine what is happenin). Instead of these "usings" I tried that way:</p> <pre><code> WriteableBitmapSource.Lock(); // this object (of type WriteableBitmap) is just MVVM ViewModel's property which is binded to MyImageControl.Source WriteableBitmapSource.Source.WritePixels(new Int32Rect(0, 0, _img.Width, _img.Height), _img.ImageData, _img.Stride * _img.Height * 3, _img.Stride, 0, 0); // image's PixelFormat is 24bppRgb </code></pre> <p>... but WritePixels method throws "Value does not fall within the expected range." Any ideas why? Any help will be much appreciated :)</p> <p>P.S. Is AForge.NET a good choice at all? Maybe there is better image processing lib?</p> <p>sorry for my english ;P</p>
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    1. COI'd imagine 10MP is your problem - any machine doing that is going to suffer. I've got Photoshop installed and on a 6MP file it takes a moment to change the image contrast/brightness.
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      1. POProcessing large bitmap images in WPF
      1. USCharleh
 

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