Digital Image Processing - Skeletonization /CPU or CUDA/

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C#

Hi,

I'd like to make a Simple Skeletonization algorythm by myself without using Aforge.Net, OpenCV, EmguCV in C#.
Can anybody help me, to understand how the skeletonization works.
I need some example algorythm for it.
I searched for it, but i didn't find any example.

My idea is the following:

1. step: I make a thresholded image - Ready (CPU & CUDA)
2. step: I have to use Erosion on tresholded image - Ready (CPU & CUDA)
3. step: I take the inverse image of step 3 - Ready (CPU & CUDA)
4. step: Skeletonization

With Aforge.Net it works fine, but i want to write it by myself.

If I will ready, I will it comply to CUDA.

Here is my Code (It has some problem: Access violation exception was unhandled. ):

class Skeletonization
	{
		private byte fg = byte.MaxValue;
		private byte bg;
 
		public Skeletonization()
		{ }
 
		public Skeletonization(byte bg, byte fg)
		{
			this.bg = bg;
			this.fg = fg;
		}
 
		public byte Background
		{
			get
			{ return this.bg; }
			set
			{ this.bg = value; }
		}
 
		public byte Foreground
		{
			get
			{ return this.fg; }
			set
			{ this.fg = value; }
		}
 
		public unsafe void SkeletonizationFunction(BitmapData sourceData, BitmapData destinationData)
		{
			int width = destinationData.Width;
			int height = destinationData.Height;
			int stride = destinationData.Stride;
			int padding = stride - width;
			byte* sourceDataPtr = (byte*)sourceData.Scan0.ToPointer();
			byte* destinationDataPtr = (byte*)destinationData.Scan0.ToPointer();
 
			for (int i = 0; i < height; i++)
			{
				int minus = -1;
				int zero = 0;
				while (zero < width)
				{
					if (minus == -1)
					{
						if ((int)*sourceDataPtr == (int)this.fg)
							minus = zero;
					}
					else if ((int)*sourceDataPtr != (int)this.fg)
					{
						destinationDataPtr[minus + (zero - minus >> 1)] = this.fg;
						minus = -1;
					}
					++zero;
					++sourceDataPtr;
				}
				if (minus != -1)
					destinationDataPtr[minus + (width - minus >> 1)] = this.fg;
				sourceDataPtr += padding;
				destinationDataPtr += stride;
			}
			for (int i = 0; i < width; i++)
			{
				byte* sourceDataPtr2 = sourceDataPtr + i;
				byte* destinationDataPtr2 = destinationDataPtr + i;
				int minus = -1;
				int zero = 0;
				while (zero < height)
				{
					if (minus == -1)
					{
//Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
						if ((int) *sourceDataPtr2 == (int)this.fg)
							minus = zero;
					}
					else if ((int) *sourceDataPtr2 != (int)this.fg)
					{
						destinationDataPtr2[((IntPtr)(stride * (minus + (zero - minus >> 1)))).ToInt64()] = this.fg;
						minus = -1;
					}
					zero++;
					sourceDataPtr2 += stride;
				}
				if (minus!=-1)
					destinationDataPtr2[((IntPtr)(stride * (minus + (height - minus >> 1)))).ToInt64()] = this.fg;
			}
		}	
	}

private void button1_Click(object sender, EventArgs e)
		{
			Bitmap bmpS = new Bitmap("x.jpg");
			Bitmap bmpD = new Bitmap(bmpS.Width, bmpS.Height);
			BitmapData bmpSourceD = bmpS.LockBits(new Rectangle(0, 0, bmpS.Width, bmpS.Height), ImageLockMode.ReadOnly, PixelFormat.Format8bppIndexed);
			BitmapData bmpDestinationD = bmpD.LockBits(new Rectangle(0, 0, bmpS.Width, bmpS.Height), ImageLockMode.ReadOnly, PixelFormat.Format8bppIndexed);
 
			Skeletonization sk = new Skeletonization();
			sk.SkeletonizationFunction(bmpSourceD, bmpDestinationD);
 
			bmpS.UnlockBits(bmpSourceD);
			bmpD.UnlockBits(bmpDestinationD);
 
			bmpD.Save("a.jpg");
		}

I would like to see more examples for it...

/Sorry for my bad English/
Thank You!

Zollie
HUN