How to solve this error - "attempted to read or write protected memory. This is often an indication that other memory is corrupt."

public void unsharp()
{
Oimg = (Bitmap)file.Clone();//input image
for (int x = 0; x < Oimg.Width; x++)
{
for (int y = 0; y < Oimg.Height; y++)
{
Color pixel = Oimg.GetPixel(x, y);

int r = pixel.R;
int g = pixel.G;
int b = pixel.B;

int[] Oarray = new int[] { r, g, b };//input image array

int[] Rarray = new int[Oarray.Length];//resultant image array

newBitmap = (Bitmap)pictureBox1.Image;//filter applied image
for (int m = 0; m < newBitmap.Width; m++)
{
for (int n = 0; n < newBitmap.Height; n++)
{
Color p = newBitmap.GetPixel(m, n);//Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
int r1 = p.R;
int g1 = p.G;
int b1 = p.B;

int[] newarray = new int[] { r1, g1, b1 };//filter applied image array

for (int e = 0; e <= Oarray.Length - 1; e++)
Rarray[e] = Oarray[e] - newarray[e];

//convert array to bitmap
Bitmap Rbmp = new Bitmap(pictureBox1.Width, pictureBox1.Height);
int stride = pictureBox1.Width * 4;
unsafe
{
fixed (int* intPtr = &Rarray[Oarray.Length-1])
{
Rbmp = new Bitmap(pictureBox1.Width, pictureBox1.Height, stride, PixelFormat.Format32bppRgb, new IntPtr(intPtr));
}
}
newBitmap = (Bitmap)Rbmp.Clone();
pictureBox1.Image = newBitmap;
}
}
}
}
}