屏幕捕获特定窗口
Screen Capture Specific Window
是否可以截屏特定窗口（也可能是另一个进程）？
目前，我正在捕获特定显示器的整个桌面，但是我真正想要的是捕获特定窗口的内容（无论其位置如何）。
是的。您所需要的只是获取要捕获并使用WinAPI函数PrintWindow的窗口句柄，例如：
// Get the window handle of calculator application.
HWND hWnd = ::FindWindow( 0, _T( "Calculator" ));
// Take screenshot.
PrintWindow( hWnd, getDC(hWnd), 0 );
这里有 PrintWindow 文档。
是的，就像捕获全屏一样简单。您只需在所需窗口上使用GetWindowDC()而不是GetDesktopWindow()，然后从该窗口BitBlt()到目标 DC。您还可以通过使用 GetWindowRect() 来获取正确的大小。
请注意，此方法还允许您从隐藏/覆盖的窗口中捕获带有边框的完整屏幕截图
。有关更多详细信息，请参阅此问题。
Windows
10中有一个新的API，winrt/Windows.Graphics.Capture.h这里有一个非常复杂的例子，Microsoft：https://github.com/microsoft/Windows.UI.Composition-Win32-Samples/tree/master/cpp/ScreenCaptureforHWND
我想创建一些肮脏的示例（非常脏），在我的示例中，您有一个简单的函数，可以获取窗口HWND并捕获它，并将其保存为ScreenShot.bmp
请注意，此函数中的错误处理很糟糕。欢迎您改进此答案！
笔记：
- 它应该完美地适用于任何窗口。即使窗口没有
WDA_NONE显示相关性 （https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-setwindowdisplayaffinity） - 当窗口不在屏幕或被另一个窗口覆盖时，它也应该工作。即使部分窗口框架在屏幕上不可见，它也会获得完整的窗口框架
- 有一个限制，即在捕获过程中，您会在很短的时间内在窗口周围看到黄色边框
法典：
#include <iostream>
#include <Windows.h>
#include <dxgi.h>
#include <inspectable.h>
#include <dxgi1_2.h>
#include <d3d11.h>
#include <winrt/Windows.Foundation.h>
#include <winrt/Windows.System.h>
#include <winrt/Windows.Graphics.Capture.h>
#include <windows.graphics.capture.interop.h>
#include <windows.graphics.directx.direct3d11.interop.h>
#include <roerrorapi.h>
#include <shlobj_core.h>
#include <dwmapi.h>
#pragma comment(lib,"Dwmapi.lib")
#pragma comment(lib,"windowsapp.lib")
void CaptureWindow(HWND hwndTarget)
{
// Init COM
winrt::init_apartment(winrt::apartment_type::multi_threaded);
// Create Direct 3D Device
winrt::com_ptr<ID3D11Device> d3dDevice;
winrt::check_hresult(D3D11CreateDevice(nullptr, D3D_DRIVER_TYPE_HARDWARE, nullptr, D3D11_CREATE_DEVICE_BGRA_SUPPORT,
nullptr, 0,D3D11_SDK_VERSION, d3dDevice.put(), nullptr, nullptr));
winrt::Windows::Graphics::DirectX::Direct3D11::IDirect3DDevice device;
const auto dxgiDevice = d3dDevice.as<IDXGIDevice>();
{
winrt::com_ptr<::IInspectable> inspectable;
winrt::check_hresult(CreateDirect3D11DeviceFromDXGIDevice(dxgiDevice.get(), inspectable.put()));
device = inspectable.as<winrt::Windows::Graphics::DirectX::Direct3D11::IDirect3DDevice>();
}
auto idxgiDevice2 = dxgiDevice.as<IDXGIDevice2>();
winrt::com_ptr<IDXGIAdapter> adapter;
winrt::check_hresult(idxgiDevice2->GetParent(winrt::guid_of<IDXGIAdapter>(), adapter.put_void()));
winrt::com_ptr<IDXGIFactory2> factory;
winrt::check_hresult(adapter->GetParent(winrt::guid_of<IDXGIFactory2>(), factory.put_void()));
ID3D11DeviceContext* d3dContext = nullptr;
d3dDevice->GetImmediateContext(&d3dContext);
RECT rect{};
DwmGetWindowAttribute(hwndTarget, DWMWA_EXTENDED_FRAME_BOUNDS, &rect, sizeof(RECT));
const auto size = winrt::Windows::Graphics::SizeInt32{rect.right - rect.left, rect.bottom - rect.top};
winrt::Windows::Graphics::Capture::Direct3D11CaptureFramePool m_framePool =
winrt::Windows::Graphics::Capture::Direct3D11CaptureFramePool::Create(
device,
winrt::Windows::Graphics::DirectX::DirectXPixelFormat::B8G8R8A8UIntNormalized,
2,
size);
const auto activationFactory = winrt::get_activation_factory<
winrt::Windows::Graphics::Capture::GraphicsCaptureItem>();
auto interopFactory = activationFactory.as<IGraphicsCaptureItemInterop>();
winrt::Windows::Graphics::Capture::GraphicsCaptureItem captureItem = {nullptr};
interopFactory->CreateForWindow(hwndTarget, winrt::guid_of<ABI::Windows::Graphics::Capture::IGraphicsCaptureItem>(),
reinterpret_cast<void**>(winrt::put_abi(captureItem)));
auto isFrameArrived = false;
winrt::com_ptr<ID3D11Texture2D> texture;
const auto session = m_framePool.CreateCaptureSession(captureItem);
m_framePool.FrameArrived([&](auto& framePool, auto&)
{
if (isFrameArrived) return;
auto frame = framePool.TryGetNextFrame();
struct __declspec(uuid("A9B3D012-3DF2-4EE3-B8D1-8695F457D3C1"))
IDirect3DDxgiInterfaceAccess : ::IUnknown
{
virtual HRESULT __stdcall GetInterface(GUID const& id, void** object) = 0;
};
auto access = frame.Surface().as<IDirect3DDxgiInterfaceAccess>();
access->GetInterface(winrt::guid_of<ID3D11Texture2D>(), texture.put_void());
isFrameArrived = true;
return;
});
session.IsCursorCaptureEnabled(false);
session.StartCapture();
// Message pump
MSG msg;
clock_t timer = clock();
while (!isFrameArrived)
{
if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE) > 0)
DispatchMessage(&msg);
if (clock() - timer > 20000)
{
// TODO: try to make here a better error handling
return;
}
}
session.Close();
D3D11_TEXTURE2D_DESC capturedTextureDesc;
texture->GetDesc(&capturedTextureDesc);
capturedTextureDesc.Usage = D3D11_USAGE_STAGING;
capturedTextureDesc.BindFlags = 0;
capturedTextureDesc.CPUAccessFlags = D3D11_CPU_ACCESS_READ;
capturedTextureDesc.MiscFlags = 0;
winrt::com_ptr<ID3D11Texture2D> userTexture = nullptr;
winrt::check_hresult(d3dDevice->CreateTexture2D(&capturedTextureDesc, NULL, userTexture.put()));
d3dContext->CopyResource(userTexture.get(), texture.get());
D3D11_MAPPED_SUBRESOURCE resource;
winrt::check_hresult(d3dContext->Map(userTexture.get(), NULL, D3D11_MAP_READ, 0, &resource));
BITMAPINFO lBmpInfo;
// BMP 32 bpp
ZeroMemory(&lBmpInfo, sizeof(BITMAPINFO));
lBmpInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
lBmpInfo.bmiHeader.biBitCount = 32;
lBmpInfo.bmiHeader.biCompression = BI_RGB;
lBmpInfo.bmiHeader.biWidth = capturedTextureDesc.Width;
lBmpInfo.bmiHeader.biHeight = capturedTextureDesc.Height;
lBmpInfo.bmiHeader.biPlanes = 1;
lBmpInfo.bmiHeader.biSizeImage = capturedTextureDesc.Width * capturedTextureDesc.Height * 4;
std::unique_ptr<BYTE> pBuf(new BYTE[lBmpInfo.bmiHeader.biSizeImage]);
UINT lBmpRowPitch = capturedTextureDesc.Width * 4;
auto sptr = static_cast<BYTE*>(resource.pData);
auto dptr = pBuf.get() + lBmpInfo.bmiHeader.biSizeImage - lBmpRowPitch;
UINT lRowPitch = std::min<UINT>(lBmpRowPitch, resource.RowPitch);
for (size_t h = 0; h < capturedTextureDesc.Height; ++h)
{
memcpy_s(dptr, lBmpRowPitch, sptr, lRowPitch);
sptr += resource.RowPitch;
dptr -= lBmpRowPitch;
}
// Save bitmap buffer into the file ScreenShot.bmp
WCHAR lMyDocPath[MAX_PATH];
winrt::check_hresult(SHGetFolderPath(nullptr, CSIDL_PERSONAL, nullptr, SHGFP_TYPE_CURRENT, lMyDocPath));
std::wstring lFilePath = L"ScreenShot.bmp";
FILE* lfile = nullptr;
if (auto lerr = _wfopen_s(&lfile, lFilePath.c_str(), L"wb"); lerr != 0)
return;
if (lfile != nullptr)
{
BITMAPFILEHEADER bmpFileHeader;
bmpFileHeader.bfReserved1 = 0;
bmpFileHeader.bfReserved2 = 0;
bmpFileHeader.bfSize = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER) + lBmpInfo.bmiHeader.biSizeImage;
bmpFileHeader.bfType = 'MB';
bmpFileHeader.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
fwrite(&bmpFileHeader, sizeof(BITMAPFILEHEADER), 1, lfile);
fwrite(&lBmpInfo.bmiHeader, sizeof(BITMAPINFOHEADER), 1, lfile);
fwrite(pBuf.get(), lBmpInfo.bmiHeader.biSizeImage, 1, lfile);
fclose(lfile);
}
return;
}
如何使用：
auto targetHwnd = FindWindow(L"Notepad",NULL); // Or user any other HWND
CaptureWindow(targetHwnd); // If it worked, it will create ScreenShot.bmp file
当我想在记事本上绘制游戏屏幕时，使用以下方法只会显示黑屏。
hdcGame := GetDC(hwndGame)
BitBlt(hdcNotpad, 0, 0, rectGame.Width(), rectGame.Height(),
hdcGame, 0, 0,
SRCCOPY
)
因此，我尝试@Roman R.的建议来捕获桌面DC GetDC(GetDesktopWindow())，然后计算屏幕的目标位置GetWindowRect并仅绘制该位置。BitBlt 或 StretchBlt
例
以下代码由 go 实现
// draw the calculator's screen on the notepad
func Example_captureWindow() {
user32dll := w32.NewUser32DLL()
gdi32dll := w32.NewGdi32DLL()
hwndScreen := user32dll.GetDesktopWindow()
hdcScreen := user32dll.GetDC(hwndScreen)
defer user32dll.ReleaseDC(hwndScreen, hdcScreen) // release when exit function
hwndCalculator := user32dll.FindWindow("ApplicationFrameWindow", "小算盤")
hwndNotepad := user32dll.FindWindow("Notepad", "")
hdcNotepad := user32dll.GetWindowDC(hwndNotepad)
defer user32dll.ReleaseDC(hwndNotepad, hdcNotepad)
var rectNotepad w32.RECT
var rectC w32.RECT
gdi32dll.SetStretchBltMode(hdcNotepad, w32.HALFTONE)
user32dll.GetWindowRect(hwndNotepad, &rectNotepad)
user32dll.GetWindowRect(hwndCalculator, &rectC)
gdi32dll.StretchBlt(
hdcNotepad, rectNotepad.Width()/4, rectNotepad.Height()/4, rectNotepad.Width()/2, rectNotepad.Height()/2, // draw screen on the center
hdcScreen, rectC.Left, rectC.Top, rectC.Width(), rectC.Height(), w32.SRCCOPY,
)
}
其他例子：
每0.1秒捕获计算器的屏幕，然后将其绘制在记事本上：源链接
按 F9 可以捕获特定设备屏幕并将其显示在记事本上。 源链接
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