1: public static Bitmap MedianFilter(Bitmap Image, int Size)

   2: {

   3:     System.Drawing.Bitmap TempBitmap = Image;

   4:     System.Drawing.Bitmap NewBitmap = new System.Drawing.Bitmap(TempBitmap.Width, TempBitmap.Height);

   5:     System.Drawing.Graphics NewGraphics = System.Drawing.Graphics.FromImage(NewBitmap);

   6:     NewGraphics.DrawImage(TempBitmap, new System.Drawing.Rectangle(0, 0, TempBitmap.Width, TempBitmap.Height), new System.Drawing.Rectangle(0, 0, TempBitmap.Width, TempBitmap.Height), System.Drawing.GraphicsUnit.Pixel);

   7:     NewGraphics.Dispose();

   8:     Random TempRandom = new Random();

   9:     int ApetureMin = -(Size / 2);

  10:     int ApetureMax = (Size / 2);

  11:     for (int x = 0; x < NewBitmap.Width; ++x)

  12:     {

  13:         for (int y = 0; y < NewBitmap.Height; ++y)

  14:         {

  15:             List<int> RValues = new List<int>();

  16:             List<int> GValues = new List<int>();

  17:             List<int> BValues = new List<int>();

  18:             for (int x2 = ApetureMin; x2 < ApetureMax; ++x2)

  19:             {

  20:                 int TempX = x + x2;

  21:                 if (TempX >= 0 && TempX < NewBitmap.Width)

  22:                 {

  23:                     for (int y2 = ApetureMin; y2 < ApetureMax; ++y2)

  24:                     {

  25:                         int TempY = y + y2;

  26:                         if (TempY >= 0 && TempY < NewBitmap.Height)

  27:                         {

  28:                             Color TempColor = TempBitmap.GetPixel(TempX, TempY);

  29:                             RValues.Add(TempColor.R);

  30:                             GValues.Add(TempColor.G);

  31:                             BValues.Add(TempColor.B);

  32:                         }

  33:                     }

  34:                 }

  35:             }

  36:             RValues.Sort();

  37:             GValues.Sort();

  38:             BValues.Sort();

  39:             Color MedianPixel = Color.FromArgb(RValues[RValues.Count / 2],

  40:                 GValues[GValues.Count / 2], 

  41:                 BValues[BValues.Count / 2]);

  42:             NewBitmap.SetPixel(x, y, MedianPixel);

  43:         }

  44:     }

  45:     return NewBitmap;

  46: }

Comments

James Craig
September 23, 2010 8:37 AM

Very cool and thank you. I've also updated the code in the post in my utility library to use LockBits: http://cul.codeplex.com/SourceControl/changeset/view/61004#707831Note that the functions are in alphabetical order, so just look for the 'M's... Your version will actually run faster though as I encapsulated the GetPixel/SetPixel in their own functions and thus have to calculate my position each time. You're doing straight pointer arithmetic (and thus wouldn't have to do as many multiplications, etc. in the long run). So very cool and thank you for the post.

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Jakub Milik
September 23, 2010 5:14 AM

Forgot to add that it assumes that your input image is in ARGB format. If it's not just change:var srcImage = image;to:var srcImage = new Bitmap(image);and dispose srcImage at the end of the function:srcImage.Dispose();

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Jakub Milik
September 23, 2010 5:10 AM

Hi. Here's a version with LockBits.[quote]public static Bitmap MedianFilter(Bitmap image, int size){unsafe{var width = image.Width;var height = image.Height;var imgSize = new Rectangle(0, 0, width, height);var srcImage = image;var srcBitmapData = srcImage.LockBits(imgSize, ImageLockMode.ReadWrite, srcImage.PixelFormat);var dstImage = new Bitmap(width, height);var dstBitmapData = dstImage.LockBits(imgSize, ImageLockMode.ReadWrite, dstImage.PixelFormat);var apetureMin = -(size / 2);var apetureMax = (size / 2);for (var y = 0; y < height; y++){var dstRow = (byte*)dstBitmapData.Scan0 + (y * dstBitmapData.Stride);for (var x = 0; x < width * 4; x += 4){

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James Craig
August 17, 2010 5:35 PM

ContextSwitch deadlock usually means that your app's UI thread isn't responding. This can be because a median filter takes a while on large images. To mitigate this you might want to look into LockBits (http://msdn.microsoft.com/en-us/library/5ey6h79d.aspx) and unsafe code. The basic concept is the same though (I'm working on rewriting all of my image classes/functions to use this in the future but for now I don't have any code that I could show you). You should be able to search and find some examples. As far as the size of the image, it's the Width and Height properties of the Bitmap object. Whatever the size of the image you send in is the size of the image that you get out.

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kasu555
August 17, 2010 12:55 PM

I set '2' as size.. The system response for small images. when i upload more colorful images the system gives an error called "ContextSwitch deadlock was detected..." .. What is the reason for the error??? If u don't mind please describe me about the size little bit further and how can i recognize the size of the image... thank you....

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James Craig
August 11, 2010 8:43 AM

Size is the size of the aperture in pixels that the median filter uses around each individual pixel (basically how far it looks left/right and up/down).

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kasu555
August 11, 2010 1:24 AM

wts size here???

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James Craig
June 22, 2010 3:08 PM

I completely agree, but I felt that some people might get confused as to what is going on if I went the unsafe route (especially considering most C# developers have never even seen the keyword actually used). This was more to show the concept than anything as switching it to use an array isn't too difficult really.

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Nick
June 22, 2010 11:43 AM

Cool function but waaay too slow for large images. You should consider stepping into unsafe code and then cycle through the image using a double array altering the byte values of pixels directly. This is a lot faster than GetPixel & SetPixel.Cheers,Nick

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Nadunwow
June 11, 2010 2:42 AM

Got it sorry

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Nadunwow
June 11, 2010 2:39 AM

Excusmi what is the size ?is it the size of the original image

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