c# - 为什么我会出现内存不足异常？

Question

这是 Form1 中的代码:

namespace ScreenVideoRecorder
{
    public partial class Form1 : Form
    {
        Magnifier20070401.MagnifierForm mf;
        ScreenCapture sc;
        Bitmap bitmap;
        Ffmpeg ffmp;

        public Form1()
        {
            InitializeComponent();

            ffmp = new Ffmpeg();
            sc = new ScreenCapture();
            //bitmap = ScreenShotDemo.ScreenCapture.CaptureScreen(true);
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void StartRecording_Click(object sender, EventArgs e)
        {
            //bitmap = ScreenShotDemo.ScreenCapture.CaptureScreen(true);
            //bitmap.Save(@"c:\ffmpeg\test.bmp");
            ffmp.Start("test.avi", 25);
            for (int i = 0; i < 500; i++)
            {
                //bitmap = ScreenShotDemo.ScreenCapture.CaptureScreen(true);
                bitmap = (Bitmap)sc.CaptureScreen();
                ffmp.PushFrame(bitmap);
                System.Threading.Thread.Sleep(35);
            }
            ffmp.Close();

这是我做的ffmpeg类的代码:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Drawing;
using System.IO.Pipes;
using System.Runtime.InteropServices;

namespace ScreenVideoRecorder
{
    class Ffmpeg
    {
        NamedPipeServerStream p;
        String pipename = "mytestpipe";
        byte[] b;
        //int i, j;
        System.Diagnostics.Process process;

        public Ffmpeg()
        {

        }

        public void Start(string FileName, int BitmapRate )
        {
            p = new NamedPipeServerStream(pipename, PipeDirection.Out, 1, PipeTransmissionMode.Byte);
            b = new byte[1920 * 1080 * 3]; // some buffer for the r g and b of pixels of an image of size 720p 
            process = new System.Diagnostics.Process();
            process.StartInfo.FileName = @"D:\pipetest\pipetest\ffmpegx86\ffmpeg.exe";
            process.EnableRaisingEvents = false;
            process.StartInfo.WorkingDirectory = @"D:\pipetest\pipetest\ffmpegx86";
            process.StartInfo.Arguments = @"-f rawvideo -pix_fmt bgr0 -video_size 1920x1080 -i \\.\pipe\mytestpipe -map 0 -c:v libx264 -r " + BitmapRate + " " + FileName;
            process.Start();

            process.StartInfo.UseShellExecute = false;
            process.StartInfo.CreateNoWindow = false;
            p.WaitForConnection();
        }

        public void PushFrame(Bitmap bmp)
        {

            int length;
            // Lock the bitmap's bits.
            //bmp = new Bitmap(1920, 1080);
            Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
            //Rectangle rect = new Rectangle(0, 0, 1280, 720);
            System.Drawing.Imaging.BitmapData bmpData =
                bmp.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadOnly,
                bmp.PixelFormat);

            int absStride = Math.Abs(bmpData.Stride);
            // Get the address of the first line.
            IntPtr ptr = bmpData.Scan0;

            // Declare an array to hold the bytes of the bitmap.
            //length = 3 * bmp.Width * bmp.Height;
            length = absStride * bmpData.Height;
            byte[] rgbValues = new byte[length];

            //Marshal.Copy(ptr, rgbValues, 0, length);
            int j = bmp.Height - 1;
            for (int i = 0; i < bmp.Height; i++)
            {
                IntPtr pointer = new IntPtr(bmpData.Scan0.ToInt32() + (bmpData.Stride * j));
                System.Runtime.InteropServices.Marshal.Copy(pointer, rgbValues, absStride * (bmp.Height - i - 1), absStride);
                j--;
            }

            p.Write(rgbValues, 0, length);

            bmp.UnlockBits(bmpData);
            /*for (j = 0; j < 25 * 10; j++) // put about 10 seconds of frames ( assumes 25 frames per second)
            {

                // put some data as rgb.. (rgb24bpp = 3 bytes per pixel)
                for (i = 0; i < b.Length; i++)
                {
                    if (((i) % 3) == 0)
                        b[i] = (byte)(i + j);
                    else
                        b[i] = 0;
                }


                p.Write(b, 0, b.Length); // send this rgb data to the pipe (ffmpeg.exe will read it..)
            }*/
        }

        public void Close()
        {
            p.Close();
            //process.Close();
        }
    }
}

这是出现内存异常的屏幕截图类。程序运行正常，几秒钟后内存不足:

using System;
using System.Runtime.InteropServices;
using System.Drawing;
using System.Drawing.Imaging;
namespace ScreenShotDemo
{
    /// <summary>
    /// Provides functions to capture the entire screen, or a particular window, and save it to a file.
    /// </summary>
    public class ScreenCapture
    {
        /// <summary>
        /// Creates an Image object containing a screen shot of the entire desktop
        /// </summary>
        /// <returns></returns>
        public Image CaptureScreen()
        {
            return CaptureWindow(User32.GetDesktopWindow());
        }
        /// <summary>
        /// Creates an Image object containing a screen shot of a specific window
        /// </summary>
        /// <param name="handle">The handle to the window. (In windows forms, this is obtained by the Handle property)</param>
        /// <returns></returns>
        public Image CaptureWindow(IntPtr handle)
        {
            // get te hDC of the target window
            IntPtr hdcSrc = User32.GetWindowDC(handle);
            // get the size
            User32.RECT windowRect = new User32.RECT();
            User32.GetWindowRect(handle, ref windowRect);
            int width = windowRect.right - windowRect.left;
            int height = windowRect.bottom - windowRect.top;
            // create a device context we can copy to
            IntPtr hdcDest = GDI32.CreateCompatibleDC(hdcSrc);
            // create a bitmap we can copy it to,
            // using GetDeviceCaps to get the width/height
            IntPtr hBitmap = GDI32.CreateCompatibleBitmap(hdcSrc, width, height);
            // select the bitmap object
            IntPtr hOld = GDI32.SelectObject(hdcDest, hBitmap);
            // bitblt over
            GDI32.BitBlt(hdcDest, 0, 0, width, height, hdcSrc, 0, 0, GDI32.SRCCOPY);
            // restore selection
            GDI32.SelectObject(hdcDest, hOld);
            // clean up 
            GDI32.DeleteDC(hdcDest);
            User32.ReleaseDC(handle, hdcSrc);
            // get a .NET image object for it
            Image img = Image.FromHbitmap(hBitmap);
            // free up the Bitmap object
            GDI32.DeleteObject(hBitmap);
            return img;
        }
        /// <summary>
        /// Captures a screen shot of a specific window, and saves it to a file
        /// </summary>
        /// <param name="handle"></param>
        /// <param name="filename"></param>
        /// <param name="format"></param>
        public void CaptureWindowToFile(IntPtr handle, string filename, ImageFormat format)
        {
            Image img = CaptureWindow(handle);
            img.Save(filename, format);
        }
        /// <summary>
        /// Captures a screen shot of the entire desktop, and saves it to a file
        /// </summary>
        /// <param name="filename"></param>
        /// <param name="format"></param>
        public void CaptureScreenToFile(string filename, ImageFormat format)
        {
            Image img = CaptureScreen();
            img.Save(filename, format);
        }

        /// <summary>
        /// Helper class containing Gdi32 API functions
        /// </summary>
        private class GDI32
        {

            public const int SRCCOPY = 0x00CC0020; // BitBlt dwRop parameter
            [DllImport("gdi32.dll")]
            public static extern bool BitBlt(IntPtr hObject, int nXDest, int nYDest,
                int nWidth, int nHeight, IntPtr hObjectSource,
                int nXSrc, int nYSrc, int dwRop);
            [DllImport("gdi32.dll")]
            public static extern IntPtr CreateCompatibleBitmap(IntPtr hDC, int nWidth,
                int nHeight);
            [DllImport("gdi32.dll")]
            public static extern IntPtr CreateCompatibleDC(IntPtr hDC);
            [DllImport("gdi32.dll")]
            public static extern bool DeleteDC(IntPtr hDC);
            [DllImport("gdi32.dll")]
            public static extern bool DeleteObject(IntPtr hObject);
            [DllImport("gdi32.dll")]
            public static extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);
        }

        /// <summary>
        /// Helper class containing User32 API functions
        /// </summary>
        private class User32
        {
            [StructLayout(LayoutKind.Sequential)]
            public struct RECT
            {
                public int left;
                public int top;
                public int right;
                public int bottom;
            }
            [DllImport("user32.dll")]
            public static extern IntPtr GetDesktopWindow();
            [DllImport("user32.dll")]
            public static extern IntPtr GetWindowDC(IntPtr hWnd);
            [DllImport("user32.dll")]
            public static extern IntPtr ReleaseDC(IntPtr hWnd, IntPtr hDC);
            [DllImport("user32.dll")]
            public static extern IntPtr GetWindowRect(IntPtr hWnd, ref RECT rect);
        }
    }
}

异常出现在 ScreenCapture 类的这一行:

Image img = Image.FromHbitmap(hBitmap);

这段代码在我兄弟的电脑上运行良好，但现在回到我家，我尝试了一下并得到了这个异常。奇怪。

这是完整的异常错误信息:

System.OutOfMemoryException was unhandled
  HResult=-2147024882
  Message=Out of memory.
  Source=System.Drawing
  StackTrace:
       at System.Drawing.Image.FromHbitmap(IntPtr hbitmap, IntPtr hpalette)
       at System.Drawing.Image.FromHbitmap(IntPtr hbitmap)
       at ScreenShotDemo.ScreenCapture.CaptureWindow(IntPtr handle) in d:\C-Sharp\ScreenVideoRecorder\ScreenVideoRecorderWorkingVersion\ScreenCapture.cs:line 49
       at ScreenShotDemo.ScreenCapture.CaptureScreen() in d:\C-Sharp\ScreenVideoRecorder\ScreenVideoRecorderWorkingVersion\ScreenCapture.cs:line 18
       at ScreenVideoRecorder.Form1.StartRecording_Click(Object sender, EventArgs e) in d:\C-Sharp\ScreenVideoRecorder\ScreenVideoRecorderWorkingVersion\Form1.cs:line 48
       at System.Windows.Forms.Control.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnClick(EventArgs e)
       at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
       at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.ButtonBase.WndProc(Message& m)
       at System.Windows.Forms.Button.WndProc(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.Run(Form mainForm)
       at ScreenVideoRecorder.Program.Main() in d:\C-Sharp\ScreenVideoRecorder\ScreenVideoRecorderWorkingVersion\Program.cs:line 18
       at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException: 

Answer 1

尝试在创建位图后释放 DC 引用。

        // get a .NET image object for it
        Image img = Image.FromHbitmap(hBitmap);            
        // clean up 
        GDI32.DeleteDC(hdcDest);
        User32.ReleaseDC(handle, hdcSrc);

编辑:

我认为您需要在完成后处理位图。尝试用 using 包围它。

        ffmp.Start("test.avi", 25);
        for (int i = 0; i < 500; i++)
        {
            using(bitmap = (Bitmap)sc.CaptureScreen())
            {
                ffmp.PushFrame(bitmap);
                System.Threading.Thread.Sleep(35);
            }
        }
        ffmp.Close();