两个线程情况下 用mutex 对bitmap加锁却不管用

Question

我想绘制mandelbrot集，用两个线程。分别绘制奇数列，偶数列。
但setpixel时候对bitmap的访问总是无法 互斥。 用 lock  monitor  mutex 都不行。private static Bitmap t = new Bitmap(640, 480);        private Thread draw1 = null;
        private Thread draw2 = null;
        private static Mutex mutex = new Mutex();        private void Draw()
        {
            draw1 = new Thread(new ThreadStart(DrawMandelbrot_Odd));
            draw2 = new Thread(new ThreadStart(DrawMandelbrot_Even));
            draw1.Start();
            draw2.Start();
            pictureBox1.Image = t;
        }        private void DrawMandelbrot_Odd() 
        {
            for (int i = 0; i < pictureBox1.Width; i += 2)
            {
             for (int j = 0; j < pictureBox1.Height; j++)
                {  
                    int k;
                    for (k = 0; k < m_Times; k++)
                    {
                      
                    }
                    Color c = ;
                    lock (this)
                    {
                        mutex.WaitOne();
                        t.SetPixel(i, j, c);
                        mutex.ReleaseMutex();
                    }
                 }
            }
        }
        private void DrawMandelbrot_Even()
        {
            for (int i = 1; i < pictureBox1.Width; i += 2)
            {
                for (int j = 0; j < pictureBox1.Height; j++)
                {
                    x0 = 0;
                    y0 = 0;
                    double p = (double)pmin + dp * i;
                    double q = (double)qmin + dq * j;
                    int k;
                    for (k = 0; k < m_Times; k++)
                    {
                        getNextIter(iterTimes, x0, y0, p, q, out x, out y);
                        r = x * x + y * y;
                        x0 = x;
                        y0 = y;
                        if (r > m_Deep)
                            break;                    }
                    red = ;
                    green = ;
                    blue = ;
                    Color c = Color.FromArgb(red, green, blue);
                    lock (this)
                    {
                        mutex.WaitOne();
                        t.SetPixel(i, j, c);
                        mutex.ReleaseMutex();
                    }
                }
            }
        }
总是在 t.SetPixel(i, j, c);处 出错， 说对象正在被使用。我少打了好多代码，

Answer 1

你是想弄出来动画效果么？这样是弄不出来的Bitmap这个对象不能被两个线程同时持有，线程互斥不是这么用的。你可以在两个线程中分别绘制图形（都持有自己的bitmap对象），然后再两个线程都完成之后通知UI线程再合并两个图片

Answer 2

用 64*48 这类小尺度画布， 偶尔可以绘制成功，大部分时候都绘制到一半，调试出错。
UI合并可以吗？ 合并之后存在哪个变量里？  picturebox.image里面行吗？ 或者某bitmap也行。求指教

Answer 3

楼主可以试试以下代码，不保证成功： 
private static Bitmap t = new Bitmap(640, 480);        private Thread draw1 = null;
        private Thread draw2 = null;
        private static object _writeLock=new object();
private autoEvents = new AutoResetEvent[]
        {
            new AutoResetEvent(false),
            new AutoResetEvent(false)
        };
        private void Draw()
        {
            draw1 = new Thread(new ThreadStart(DrawMandelbrot_Odd));
            draw2 = new Thread(new ThreadStart(DrawMandelbrot_Even));
            draw1.Start();
            draw2.Start();
WaitHandle.WaitAll(autoEvents);
            pictureBox1.Image = t;
        }        private void DrawMandelbrot_Odd()
        {
            for (int i = 0; i < pictureBox1.Width; i += 2)
            {
for (int j = 0; j < pictureBox1.Height; j++)
                { 
                    int k;
                    for (k = 0; k < m_Times; k++)
                    {
                      
                    }
                    Color c = ;
                    SetPixel(i, j, c);
                }
            }
autoEvents[0].Set();
        }
        private void DrawMandelbrot_Even()
        {
            for (int i = 1; i < pictureBox1.Width; i += 2)
            {
                for (int j = 0; j < pictureBox1.Height; j++)
                {
                    x0 = 0;
                    y0 = 0;
                    double p = (double)pmin + dp * i;
                    double q = (double)qmin + dq * j;
                    int k;
                    for (k = 0; k < m_Times; k++)
                    {
                        getNextIter(iterTimes, x0, y0, p, q, out x, out y);
                        r = x * x + y * y;
                        x0 = x;
                        y0 = y;
                        if (r > m_Deep)
                            break;                    }
                    red = ;
                    green = ;
                    blue = ;
                    Color c = Color.FromArgb(red, green, blue);
                    SetPixel(i, j, c);
                }
            }
autoEvents[1].Set();
        } private void SetPixel(int i,int j,Color c)
{
lock(_writeLock)
{
try
{
 t.SetPixel(i, j, c);
}
catch ()
{
}
}
}