我正在使用C++编写一些代码，以给定窗口句柄拍摄另一个应用程序的屏幕截图。我使用的方法是使用BitBlt。我的应用成功地拍摄了屏幕截图，并且我有一个函数将该图像数据保存到bmp文件中。
但是屏幕截图包含了窗口的边框和标题栏。根据我的理解，GetClientRect应该排除窗口的边框和标题栏。我了解到GetWindowRect返回用户桌面内的坐标，而GetClientRect返回相对于应用程序自身的坐标。
我发现在我的屏幕截图中，标题栏和左边框是可见的，但右边框和应用程序的底部被裁剪掉了。因此，我认为如果我想要排除标题和边框，那么我需要对GetWindowRect和GetClientRect进行某种组合，并使用关于窗口本身的信息来偏移GetClientRect的尺寸，例如窗口的标题栏高度。
这是否正确，或者我下面的代码有问题？
#include <Windows.h>
#include "ScreenshotManager.h"
namespace Managers {
ScreenshotManager::ScreenshotManager(HWND gameHandle) {
// get a device context for the window
m_gameContext = GetWindowDC(gameHandle);
// create a compatible device context for bitblt
m_bitmapContext = CreateCompatibleDC(m_gameContext);
// get window client area dimensions
GetClientRect(gameHandle, &m_gameClientArea);
}
bool ScreenshotManager::TakeScreenshot() {
// create a compatible bitmap for the game screenshots
m_bitmap = CreateCompatibleBitmap(m_gameContext, m_gameClientArea.right, m_gameClientArea.bottom);
// select the bitmap into the compatible device context
SelectObject(m_bitmapContext, m_bitmap);
// perform bit block transfer
if (BitBlt(m_bitmapContext, 0, 0, m_gameClientArea.right, m_gameClientArea.bottom, m_gameContext, 0, 0, SRCCOPY) == false)
return false;
// get information about the taken screenshot
GetObject(m_bitmap, sizeof(BITMAP), &m_bitmapInformation);
return true;
}
void ScreenshotManager::SaveScreenshot(LPCWSTR outputPath) {
BITMAPFILEHEADER bmfHeader;
BITMAPINFOHEADER bi;
bi.biSize = sizeof(BITMAPINFOHEADER);
bi.biWidth = m_bitmapInformation.bmWidth;
bi.biHeight = m_bitmapInformation.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 = ((m_bitmapInformation.bmWidth * bi.biBitCount + 31) / 32) * 4 * m_bitmapInformation.bmHeight;
// Starting with 32-bit Windows, GlobalAlloc and LocalAlloc are implemented as wrapper functions that
// call HeapAlloc using a handle to the process's default heap. Therefore, GlobalAlloc and LocalAlloc
// have greater overhead than HeapAlloc.
HANDLE hDIB = GlobalAlloc(GHND,dwBmpSize);
char *lpbitmap = (char *)GlobalLock(hDIB);
// Gets the "bits" from the bitmap and copies them into a buffer which is pointed to by lpbitmap.
GetDIBits(m_gameContext, m_bitmap, 0, (UINT)m_bitmapInformation.bmHeight, lpbitmap, (BITMAPINFO *)&bi, DIB_RGB_COLORS);
// A file is created, this is where we will save the screen capture.
HANDLE hFile = CreateFile(outputPath, GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
// Add the size of the headers to the size of the bitmap to get the total file size
DWORD dwSizeofDIB = dwBmpSize + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
//Offset to where the actual bitmap bits start.
bmfHeader.bfOffBits = (DWORD)sizeof(BITMAPFILEHEADER) + (DWORD)sizeof(BITMAPINFOHEADER);
//Size of the file
bmfHeader.bfSize = dwSizeofDIB;
//bfType must always be BM for Bitmaps
bmfHeader.bfType = 0x4D42; //BM
DWORD dwBytesWritten = 0;
WriteFile(hFile, (LPSTR)&bmfHeader, sizeof(BITMAPFILEHEADER), &dwBytesWritten, NULL);
WriteFile(hFile, (LPSTR)&bi, sizeof(BITMAPINFOHEADER), &dwBytesWritten, NULL);
WriteFile(hFile, (LPSTR)lpbitmap, dwBmpSize, &dwBytesWritten, NULL);
//Unlock and Free the DIB from the heap
GlobalUnlock(hDIB);
GlobalFree(hDIB);
//Close the handle for the file that was created
CloseHandle(hFile);
}
}
PrintWindow函数，因为根据文档，它似乎将屏幕截图的实际处理推迟到您正在截图的程序中。这不是比BitBlt方法更不兼容吗？ - Ryan