c++ windows 截取指定进程主窗口

在C++中，截取指定进程的主窗口可以通过Windows API实现。以下是一个简单的示例代码，展示了如何获取指定进程的主窗口句柄并进行截屏：

#include <windows.h>
#include <iostream>
#include <string>

// 获取指定进程ID的主窗口句柄
HWND GetProcessMainWindow(DWORD processID) {
    HWND hwnd = NULL;
    DWORD windowProcessID = 0;

    // 枚举所有顶级窗口
    EnumWindows([](HWND hwnd, LPARAM lParam) -> BOOL {
        DWORD processID = 0;
        GetWindowThreadProcessId(hwnd, &processID);

        // 检查窗口是否可见且具有标题
        if (IsWindowVisible(hwnd) && GetWindowTextLength(hwnd) > 0) {
            DWORD* processIDPtr = reinterpret_cast<DWORD*>(lParam);
            if (processID == *processIDPtr) {
                // 找到目标进程的主窗口
                SetLastError(ERROR_SUCCESS);
                SetWindowLongPtr(hwnd, GWLP_USERDATA, (LONG_PTR)processIDPtr);
                return FALSE; // 停止枚举
            }
        }
        return TRUE; // 继续枚举
    }, (LPARAM)&processID);

    if (GetLastError() == ERROR_SUCCESS) {
        hwnd = FindWindowEx(NULL, NULL, NULL, NULL);
        while (hwnd != NULL) {
            if (GetWindowLongPtr(hwnd, GWLP_USERDATA) == (LONG_PTR)&processID) {
                break;
            }
            hwnd = GetWindow(hwnd, GW_HWNDNEXT);
        }
    }

    return hwnd;
}

// 截取指定窗口的图像
bool CaptureWindow(HWND hwnd, const std::string& filename) {
    if (!hwnd) return false;

    RECT rect;
    if (!GetWindowRect(hwnd, &rect)) return false;

    int width = rect.right - rect.left;
    int height = rect.bottom - rect.top;

    // 创建设备上下文
    HDC hdcScreen = GetDC(hwnd);
    HDC hdcWindow = CreateCompatibleDC(hdcScreen);
    HBITMAP hBitmap = CreateCompatibleBitmap(hdcScreen, width, height);
    SelectObject(hdcWindow, hBitmap);

    // 截取窗口图像
    if (!BitBlt(hdcWindow, 0, 0, width, height, hdcScreen, 0, 0, SRCCOPY)) {
        DeleteObject(hBitmap);
        DeleteDC(hdcWindow);
        ReleaseDC(hwnd, hdcScreen);
        return false;
    }

    // 保存图像到文件
    BITMAP bmp;
    GetObject(hBitmap, sizeof(BITMAP), &bmp);

    BITMAPFILEHEADER bmfHeader;
    BITMAPINFOHEADER bi;

    bi.biSize = sizeof(BITMAPINFOHEADER);
    bi.biWidth = bmp.bmWidth;
    bi.biHeight = bmp.bmHeight;
    bi.biPlanes = 1;
    bi.biBitCount = 32;
    bi.biCompression = BI_RGB;
    bi.biSizeImage = 0;
    bi.biXPelsPerMeter = 0;
    bi.biYPelsPerMeter = 0;
    bi.biClrUsed = 0;
    bi.biClrImportant = 0;

    DWORD dwBmpSize = ((bmp.bmWidth * bi.biBitCount + 31) / 32) * 4 * bmp.bmHeight;

    // 创建文件
    HANDLE hFile = CreateFileA(filename.c_str(), GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
    if (hFile == INVALID_HANDLE_VALUE) {
        DeleteObject(hBitmap);
        DeleteDC(hdcWindow);
        ReleaseDC(hwnd, hdcScreen);
        return false;
    }

    // 写入文件头
    DWORD dwSizeOfDIB = dwBmpSize + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
    bmfHeader.bfOffBits = (DWORD)sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
    bmfHeader.bfSize = dwSizeOfDIB;
    bmfHeader.bfType = 0x4D42; // BM

    DWORD dwBytesWritten = 0;
    WriteFile(hFile, (LPVOID)&bmfHeader, sizeof(BITMAPFILEHEADER), &dwBytesWritten, NULL);
    WriteFile(hFile, (LPVOID)&bi, sizeof(BITMAPINFOHEADER), &dwBytesWritten, NULL);

    // 写入位图数据
    BYTE* lpBits = new BYTE[dwBmpSize];
    GetDIBits(hdcWindow, hBitmap, 0, (UINT)bmp.bmHeight, lpBits, (BITMAPINFO*)&bi, DIB_RGB_COLORS);

    WriteFile(hFile, (LPVOID)lpBits, dwBmpSize, &dwBytesWritten, NULL);

    // 清理
    delete[] lpBits;
    CloseHandle(hFile);
    DeleteObject(hBitmap);
    DeleteDC(hdcWindow);
    ReleaseDC(hwnd, hdcScreen);

    return true;
}

int main() {
    DWORD processID = 1234; // 替换为目标进程的ID
    HWND hwnd = GetProcessMainWindow(processID);

    if (hwnd) {
        std::cout << "找到主窗口句柄: " << hwnd << std::endl;
        CaptureWindow(hwnd, "screenshot.bmp");
        std::cout << "截屏保存为 screenshot.bmp" << std::endl;
    } else {
        std::cout << "未找到主窗口句柄" << std::endl;
    }

    return 0;
}