using System.Drawing.Drawing2D;
using System.Drawing.Imaging;Bitmap image=new Bitmap(pictrueBox1.Image);
int iW,iH,r,g,b;
Color cOld=new Color;for(iW=1;iW<image.Width;iW++)
{
    for(iH=1;iH<image.Height;iH++)
   {   
     cOld=image.GetPixel(iW,iH);
     r=cOld.R;
     g=cOld.G;
     b=cOld.B
   }
}