4

我正在使用以下代码来捕获屏幕并将其复制到 BitmapSource。每 400 毫秒通过 DispatcherTimer 连续调用该方法。首先，我将此代码用于 .NET Framework 3.5，然后我切换到 Framework 4.0。当程序运行一段时间（比如说 15 分钟）时，它在调用 GetHBitmap 期间突然崩溃并出现“GDI+ 中的通用错误”。

当我切换到 .NET 4.0 时，我不得不注释掉引发 SEHException 的 CloseHandle() 调用。也许这会导致问题，也许不会。

所以，这是我的代码。我希望有人能帮帮忙...

// The code is based on an example by Charles Petzold
// http://www.charlespetzold.com/pwcs/ReadingPixelsFromTheScreen.html

// Import external Win32 functions

// BitBlt is used for the bit by bit block copy of the screen content
[DllImport("gdi32.dll")]
private static extern bool BitBlt(IntPtr hdcDst, int xDst, int yDst, int cx, int cy,
                                    IntPtr hdcSrc, int xSrc, int ySrc, uint ulRop);

// DeleteObject is used to delete the bitmap handle
[DllImport("gdi32.dll")]
private static extern bool DeleteObject(IntPtr hObject);

// CreateDC is used to create a graphics handle to the screen
[DllImport("gdi32.dll")]
private static extern IntPtr CreateDC(string lpszDriver, string lpszDevice, string lpszOutput, IntPtr lpInitData);

// CloseHandle is used to close the bitmap handle, which does not work with Framework 4 :(
// [DllImport("Kernel32")]
// private static extern bool CloseHandle(IntPtr handle);

public static void getBitmap(ref BitmapSource bms)
{
    // define the raster-operation code for the BitBlt method
    // SRCOPY copies the source directly to the destination
    const int SRCCOPY = 0x00CC0020;

    // The screenshot will be stored here
    Bitmap bm;

    // Get a Graphics object associated with the screen
    Screen s = UIHelper.getScreenHandle();
    Graphics grfxScreen = Graphics.FromHdc(CreateDC(null, s.DeviceName, null,
        IntPtr.Zero));

    // Create a bitmap the size of the screen.
    bm = new Bitmap((int)grfxScreen.VisibleClipBounds.Width,
                    (int)grfxScreen.VisibleClipBounds.Height, grfxScreen);

    // Create a Graphics object associated with the bitmap
    Graphics grfxBitmap = Graphics.FromImage(bm);

    // Get handles associated with the Graphics objects
    IntPtr hdcScreen = grfxScreen.GetHdc();
    IntPtr hdcBitmap = grfxBitmap.GetHdc();

    // Do the bitblt from the screen to the bitmap
    BitBlt(hdcBitmap, 0, 0, bm.Width, bm.Height,
            hdcScreen, 0, 0, SRCCOPY);

    // Release the device contexts.
    grfxBitmap.ReleaseHdc(hdcBitmap);
    grfxScreen.ReleaseHdc(hdcScreen);

    // convert the Bitmap to BitmapSource
    IntPtr hBitmap = bm.GetHbitmap();         // Application crashes here after a while...

    //System.Runtime.InteropServices.ExternalException was unhandled
    //  Message=Generic Error in GDI+.
    //  Source=System.Drawing
    //  ErrorCode=-2147467259
    //  StackTrace:
    //       at System.Drawing.Bitmap.GetHbitmap(Color background)
    //       at System.Drawing.Bitmap.GetHbitmap()

    if (bms != null) bms = null; // Dispose bms if it holds content
    bms = System.Windows.Interop.Imaging.CreateBitmapSourceFromHBitmap(
        hBitmap,
        IntPtr.Zero,
        Int32Rect.Empty,
        System.Windows.Media.Imaging.BitmapSizeOptions.FromEmptyOptions());

    // tidy up

    // CloseHandle throws SEHException using Framework 4
    // CloseHandle(hBitmap);

    DeleteObject(hBitmap);
    hBitmap = IntPtr.Zero;
    bm.Dispose();
    hdcBitmap = IntPtr.Zero;
    hdcScreen = IntPtr.Zero;
    grfxBitmap.Dispose();
    grfxScreen.Dispose();
    GC.Collect();

}
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3 回答 3

10

您的代码正在泄漏 CreateDC() 返回的句柄。它必须通过调用 DeleteDC() 来释放。在程序泄露 10,000 个句柄后，Windows 将不再提供。您可以使用 TaskMgr.exe 的“进程”选项卡诊断此类泄漏。查看 + 选择列以添加句柄、用户对象和 GDI 对象的列。GDI Objects 是一个稳步增长的对象。

使用 Graphics.CopyFromScreen() 绝对是遇到此类麻烦的较小方式。但是，它有一个错误。它和您当前的代码都不会捕获任何分层窗口。这需要托管代码中带有 BitBlt() 的 CAPTUREBLT 选项、CopyPixelOperation.CaptureBlt 选项。CopyFromScreen() 摸索这个选项，不会让你通过它。

回到 BitBlt() 来解决这个问题。您会在我在此网页上的回答中找到已知可工作的代码。

于 2011-07-06T15:55:25.560 回答
1

可能是一段时间后，GDI 需要更多时间。要对此进行测试，您可以增加 Timer.Interval。

但是为什么通过 Petzold 这么复杂呢？

using System.Drawing.Imaging;


private static Bitmap bmp;

private static Graphics gfx;

然后在你的方法中：

bmp = new Bitmap(Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height, PixelFormat.Format32bppArgb);

gfx = Graphics.FromImage(bmp);

gfx.CopyFromScreen(Screen.PrimaryScreen.Bounds.X, Screen.PrimaryScreen.Bounds.Y, 0, 0, Screen.PrimaryScreen.Bounds.Size, CopyPixelOperation.SourceCopy);
于 2011-07-06T13:58:58.817 回答
1

这是重新编写的代码，将 Petzold 的代码与 Hans Passant 的示例混合在一起（仍然缺少 CloseHandle(hBitmap) 调用）：

[DllImport("gdi32.dll")]
static extern bool BitBlt(IntPtr hdcDest, int xDest, int yDest, int
wDest, int hDest, IntPtr hdcSource, int xSrc, int ySrc, CopyPixelOperation rop);

[DllImport("gdi32.dll")]
static extern IntPtr DeleteDC(IntPtr hDc);

[DllImport("gdi32.dll")]
static extern IntPtr DeleteObject(IntPtr hDc);

[DllImport("gdi32.dll")]
static extern IntPtr CreateCompatibleBitmap(IntPtr hdc, int nWidth, int nHeight);

[DllImport("gdi32.dll")]
static extern IntPtr CreateCompatibleDC(IntPtr hdc);

[DllImport("gdi32.dll")]
static extern IntPtr SelectObject(IntPtr hdc, IntPtr bmp);

[DllImport("gdi32.dll")]
private static extern IntPtr CreateDC(string lpszDriver, string lpszDevice, string lpszOutput, IntPtr lpInitData);

// get the screen handle and size
Screen s = UIHelper.getScreenHandle();
Size sz = s.Bounds.Size;

// capture the screen
IntPtr hSrce = CreateDC(null, s.DeviceName, null, IntPtr.Zero);
IntPtr hDest = CreateCompatibleDC(hSrce);
IntPtr hBmp = CreateCompatibleBitmap(hSrce, sz.Width, sz.Height);
IntPtr hOldBmp = SelectObject(hDest, hBmp);
bool b = BitBlt(hDest, 0, 0, sz.Width, sz.Height, hSrce, 0, 0, CopyPixelOperation.SourceCopy | CopyPixelOperation.CaptureBlt);
Bitmap bm = Bitmap.FromHbitmap(hBmp);
SelectObject(hDest, hOldBmp);

// convert the Bitmap to BitmapSource
IntPtr hBitmap = bm.GetHbitmap();

// Dispose bms if it holds content, Garbage Collector will do the cleaning
if (bms != null) bms = null;

// create BitmapSource from Bitmap
bms = System.Windows.Interop.Imaging.CreateBitmapSourceFromHBitmap(
    hBitmap,
    IntPtr.Zero,
    Int32Rect.Empty,
    System.Windows.Media.Imaging.BitmapSizeOptions.FromEmptyOptions());

// tidy up

// CloseHandle throws SEHException using Framework 4
// CloseHandle(hBitmap);

DeleteObject(hBitmap);
hBitmap = IntPtr.Zero;

DeleteObject(hBmp);
DeleteDC(hDest);
DeleteDC(hSrce);

bm.Dispose();
GC.Collect();
于 2011-07-07T11:31:51.020 回答