Question

我正在制作一个ms绘画应用程序，绘制内部并填充内部。我写了填充conture的递归函数。它工作正常，但如果conture太大程序抛出stackoverflow异常。我怎么解决这个问题？？我甚至无法捕捉到这个例外（（

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {

[DllImport( "user32.dll" )]
static extern IntPtr GetDC( IntPtr hWnd );
[DllImport( "user32.dll" )]
static extern int ReleaseDC( IntPtr hWnd, IntPtr hDC );
[DllImport( "gdi32.dll" )]
static extern int GetPixel( IntPtr hDC, int x, int y );
[DllImport( "gdi32.dll" )]
static extern int SetPixel( IntPtr hDC, int x, int y, int color );

static public Color GetPixel( Control control, int x, int y )
{
    Color color = Color.Empty;
    if (control != null)
    {
        IntPtr hDC = GetDC( control.Handle );
        int colorRef = GetPixel( hDC, x, y );
        color = Color.FromArgb(
            (int)(colorRef & 0x000000FF),
            (int)(colorRef & 0x0000FF00) >> 8,
            (int)(colorRef & 0x00FF0000) >> 16 );
        ReleaseDC( control.Handle, hDC );
    }
    return color;
}
static public void SetPixel( Control control, int x, int y, Color color )
{
    if (control != null)
    {
        IntPtr hDC = GetDC( control.Handle );
        int argb = color.ToArgb();
        int colorRef =
            (int)((argb & 0x00FF0000) >> 16) |
            (int)(argb & 0x0000FF00) |
            (int)((argb & 0x000000FF) << 16);
        SetPixel( hDC, x, y, colorRef );
        ReleaseDC( control.Handle, hDC );
    }
}

        int oldX, oldY;
        public Form1()
        {
            InitializeComponent();
        }



        private void button1_Click(object sender, EventArgs e)
        {
            Graphics g = panel1.CreateGraphics();
            g.Clear(panel1.BackColor);
        }
        bool paint;

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void panel1_MouseDown(object sender, MouseEventArgs e)
        {
            oldX = e.X;
            oldY = e.Y;
            paint = true;
        }

        private void panel1_MouseUp(object sender, MouseEventArgs e)
        {
            paint = false;
        }

        private void panel1_MouseMove(object sender, MouseEventArgs e)
        {
            if (paint)
            {
                Graphics g = panel1.CreateGraphics();
                Pen p = new Pen(Color.Black);
                g.DrawLine(p, oldX, oldY, e.X, e.Y);
                oldX = e.X;
                oldY = e.Y;
            }
        }

        private void panel1_MouseDoubleClick(object sender, MouseEventArgs e)
        {
            fill(e.X, e.Y, Color.Black, Color.Red);
            Color c = GetPixel(panel1, e.X, e.Y);
            ClearButton.BackColor = c;
            label1.Text = e.X + " " + e.Y;

        }
        private void fill(int x, int y, Color border, Color c) {

            Color PointedColor = GetPixel(panel1, x, y);

            try { 
                        if (PointedColor.R != border.R && PointedColor.G != border.G && PointedColor.B != border.B &&
                PointedColor.R != c.R && PointedColor.G != c.G && PointedColor.B != c.B &&
                x >= 0 && x < panel1.Size.Width && y >= 0 && y < panel1.Size.Height)
            {
                SetPixel(panel1, x, y, c);

                fill(x - 1, y, border, c);
                fill(x + 1, y, border, c);
                fill(x, y - 1, border, c);
                fill(x, y + 1, border, c);

            }

            }
            catch(System.StackOverflowException e)
            {
                label1.Text = e.Message;
            }

        }
    }
}

Answer 1

您应该使用非递归填充算法。

有关说明，请参阅维基百科{{3p>

Bob Powell有一些源代码article。

Answer 2

您不能按设计捕捉StackOverflowException：

从.NET Framework 2.0版开始，try-catch块无法捕获StackOverflowException对象，默认情况下会终止相应的进程。因此，建议用户编写代码以检测并防止堆栈溢出。例如，如果您的应用程序依赖于递归，请使用计数器或状态条件来终止递归循环。

我确信有更有效的方法可以实现这一目标。但是，要启动您，您可以通过将调用堆栈重新设置为Stack<T>来将递归转换为迭代：

private void fill(int xInitial, int yInitial, Color border, Color c) 
{
    var remaining = new Stack<Tuple<int, int>>();
    remaining.Push(Tuple.Create(xInitial, yInitial));

    while (remaining.Any())
    {
        var next = remaining.Pop();
        int x = next.Item1;
        int y = next.Item2;

        Color PointedColor = GetPixel(panel1, x, y);

        if (PointedColor.R != border.R && 
            PointedColor.G != border.G && 
            PointedColor.B != border.B &&
            PointedColor.R != c.R && 
            PointedColor.G != c.G && 
            PointedColor.B != c.B &&
            x >= 0 && 
            x < panel1.Size.Width && 
            y >= 0 && 
            y < panel1.Size.Height)
        {
            SetPixel(panel1, x, y, c);
            remaining.Push(Tuple.Create(x - 1, y));
            remaining.Push(Tuple.Create(x + 1, y));
            remaining.Push(Tuple.Create(x, y - 1));
            remaining.Push(Tuple.Create(x, y + 1));
        }
    }
}

递归中的stackoverflow

2 个答案: