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使用GetHBitmap的GDI中的一般错误（WPF4 / C＃）

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我正在使用以下代码捕获屏幕并将其复制到BitmapSource中 . 每400ms通过DispatcherTimer连续调用该方法 . 首先，我在.NET Framework 3.5中使用了此代码，然后切换到Framework 4.0 . 当程序运行一段时间（假设15分钟）时，在GetHBitmap调用期间突然崩溃，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CloseHandle（）调用，它引发了一个SEHException . 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();

}
c# .net c#-4.0 gdi+ wpf-4.0

3 回答

  • 10

    您的代码泄漏了CreateDC（）返回的句柄 . 它必须通过调用DeleteDC（）来释放 . 程序泄漏10,000个句柄后，Windows将不再提供它 . 您可以使用TaskMgr.exe，Processes选项卡诊断这些泄漏 . 查看选择列以添加句柄，用户对象和GDI对象的列 . GDI Objects正在稳步增长 .

    使用Graphics.CopyFromScreen（）绝对是遇到这种麻烦的较小方法 . 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CAPTUREBLT选项与托管代码中的BitBlt（），CopyPixelOperation.CaptureBlt选项 . CopyFromScreen（）摸索了此选项，不允许您传递它 .

    回到BitBlt（）来解决这个问题 . 你会在this web page的答案中找到已知的工作代码 .

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  • 1

    可能有一段时间GDI需要更多时间 . 要测试它，可以增加Timer.Interval .

    但是为什么Petzold如此复杂？

    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);
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  • 1

    这是重写的代码，将Petzold的代码与Hans Passant的例子混合在一起（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();
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