Converting Image to Black and White In C#

Today I need to convert an image to black and white. For this I googled and get some help. Here I am going to share my experience.

Here I am adding the class what I used in my program. And I dont get any wrong yet.

Here is the class:

using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;

namespace BitonalConverter
{
public static class Converter
{

public static Bitmap ConvertToBitonal(Bitmap original)
{
Bitmap source = null;

// If original bitmap is not already in 32 BPP, ARGB format, then convert
if (original.PixelFormat != PixelFormat.Format32bppArgb)
{
source = new Bitmap(original.Width, original.Height, PixelFormat.Format32bppArgb);
source.SetResolution(original.HorizontalResolution, original.VerticalResolution);
using (Graphics g = Graphics.FromImage(source))
{
g.DrawImageUnscaled(original, 0, 0);
}
}
else
{
source = original;
}

// Lock source bitmap in memory
BitmapData sourceData = source.LockBits(new Rectangle(0, 0, source.Width, source.Height), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);

// Copy image data to binary array
int imageSize = sourceData.Stride * sourceData.Height;
byte[] sourceBuffer = new byte[imageSize];
Marshal.Copy(sourceData.Scan0, sourceBuffer, 0, imageSize);

// Unlock source bitmap
source.UnlockBits(sourceData);

// Create destination bitmap
Bitmap destination = new Bitmap(source.Width, source.Height, PixelFormat.Format1bppIndexed);
destination.SetResolution(original.HorizontalResolution, original.VerticalResolution);

// Lock destination bitmap in memory
BitmapData destinationData = destination.LockBits(new Rectangle(0, 0, destination.Width, destination.Height), ImageLockMode.WriteOnly, PixelFormat.Format1bppIndexed);

// Create destination buffer
imageSize = destinationData.Stride * destinationData.Height;
byte[] destinationBuffer = new byte[imageSize];

int sourceIndex = 0;
int destinationIndex = 0;
int pixelTotal = 0;
byte destinationValue = 0;
int pixelValue = 128;
int height = source.Height;
int width = source.Width;
int threshold = 500;

// Iterate lines
for (int y = 0; y < sourceindex =" y" destinationindex =" y" destinationvalue =" 0;" pixelvalue =" 128;" x =" 0;" pixeltotal =" sourceBuffer[sourceIndex]"> threshold)
{
destinationValue += (byte)pixelValue;
}
if (pixelValue == 1)
{
destinationBuffer[destinationIndex] = destinationValue;
destinationIndex++;
destinationValue = 0;
pixelValue = 128;
}
else
{
pixelValue >>= 1;
}
sourceIndex += 4;
}
if (pixelValue != 128)
{
destinationBuffer[destinationIndex] = destinationValue;
}
}

// Copy binary image data to destination bitmap
Marshal.Copy(destinationBuffer, 0, destinationData.Scan0, imageSize);

// Unlock destination bitmap
destination.UnlockBits(destinationData);

// Dispose of source if not originally supplied bitmap
if (source != original)
{
source.Dispose();
}

/**************/
// to change the dpi of image you can do the following you can take the value of dpi //from user here I initialize i 200
int dpi=200;
destination.SetResolution(dpi, dpi);
/********/

// Return
return destination;
}
}
}


You have to pass the image in this function
ConvertToBitonal(Bitmap original)
then this class will return the converted image.

Here is the screen shot of my project.