以一个倾斜十字为例试着找了一下中心点，没优化，不知道行不行。
int centerx = -1;
int centery = -1;
Bitmap bp;
public Form1()
{
InitializeComponent();
}
unsafe private void button1_Click_1(object sender, EventArgs e)
{
bp = (Bitmap)Bitmap.FromFile("e:\\test.bmp");
BitmapData data = bp.LockBits(new Rectangle(0, 0, bp.Width, bp.Height), ImageLockMode.ReadWrite, PixelFormat.Format32bppArgb);
Dictionary<uint, List<Point>> colorpoints = new Dictionary<uint, List<Point>>();
uint* p = (uint*)data.Scan0;
for (int i = 0; i < bp.Width; i++)
{
for (int j = 0; j < bp.Height; j++)
{
uint color = p[j * bp.Width + i];
if (!colorpoints.Keys.Contains(color))
colorpoints.Add(color, new List<Point>());
else
colorpoints[color].Add(new Point(i, j));
}
}
var cross = colorpoints.OrderByDescending(x => x.Value.Count).Select(y => y.Key).ToArray()[1];
List<Point> list = colorpoints[cross];
int leftx = list.Min(x => x.X);
int rightx = list.Max(x => x.X);
int topy = list.Min(x => x.Y);
int bottomy = list.Max(x => x.Y);
centerx = (leftx + rightx) / 2;
centery = (topy + bottomy) / 2;
for (int i = centerx - 10; i < centerx + 11; i++)
{
for (int j = centery - 10; j < centery + 11; j++)
{
p[j * bp.Width + i] = 0xffffffff;
}
}
bp.UnlockBits(data);
Invalidate();
}
protected override void OnPaint(PaintEventArgs e)
{
if(centerx == -1)
return;
e.Graphics.DrawImage(bp, new Point(0, 0));
}
