C#图像对比度调整的方法

//定义对比度调整函数private static Bitmap ContrastP(Bitmap a, double v){ System.Drawing.Imaging.BitmapData bmpData = a.LockBits(new Rectangle(0, 0, a.Width, a.Height), System.Drawing.Imaging.ImageLockMode.ReadWrite, System.Drawing.Imaging.PixelFormat.Format24bppRgb); int bytes = a.Width * a.Height * 3; IntPtr ptr = bmpData.Scan0; int stride = bmpData.Stride; unsafe {  byte* p = (byte*)ptr;  int temp;  for (int j = 0; j < a.Height; j++)  {   for (int i = 0; i < a.Width * 3; i++)   {   temp = (int)((p[0] - 127) * v + 127);   temp = (temp > 255) ? 255 : temp < 0 ? 0 : temp;   p[0] = (byte)temp;   p++;   }   p += stride - a.Width * 3;  } } a.UnlockBits(bmpData); return a;}