[已解决]关于获取屏幕截图后在内存数据指针的问题

wyxhehe · 发表于 2020-8-19 21:46:34

本人想利用如下代码进行截屏，然后在内存中直接获取位图数据区域指针，总是不成功（n总是为0），望高人解答，不胜感激！
HDC hScreen = ::GetDC(NULL);
HDC hCompDC = CreateCompatibleDC(hScreen);
HBITMAP hBmp,hOld;
BITMAPINFOHEADER bih;
//取屏幕宽度和高度
int nWidth = GetSystemMetrics(SM_CXSCREEN);
int nHeight = GetSystemMetrics(SM_CYSCREEN);
//创建Bitmap对象
hBmp = CreateCompatibleBitmap(hScreen, nWidth, nHeight);
hOld = (HBITMAP)SelectObject(hCompDC, hBmp);
BitBlt(hCompDC, 0, 0, nWidth, nHeight, hScreen, 0, 0, SRCCOPY);

char* pData ;
int n = ::GetDIBits(hCompDC, hBmp, 0, nHeight, pData, (BITMAPINFO*)&bih, DIB_RGB_COLORS);

最佳答案

月排行榜 / 总排行榜

dbjs

2020-8-20 11:41:59

从微软拿过来的地址

int CaptureAnImage(HWND hWnd)
{
HDC hdcScreen;
HDC hdcWindow;
HDC hdcMemDC = NULL;
HBITMAP hbmScreen = NULL;
BITMAP bmpScreen;
// Retrieve the handle to a display device context for the client
// area of the window.
hdcScreen = GetDC(NULL);
hdcWindow = GetDC(hWnd);
// Create a compatible DC which is used in a BitBlt from the window DC
hdcMemDC = CreateCompatibleDC(hdcWindow);
if(!hdcMemDC)
{
MessageBox(hWnd, L"CreateCompatibleDC has failed",L"Failed", MB_OK);
goto done;
}
// Get the client area for size calculation
RECT rcClient;
GetClientRect(hWnd, &rcClient);
//This is the best stretch mode
SetStretchBltMode(hdcWindow,HALFTONE);
//The source DC is the entire screen and the destination DC is the current window (HWND)
if(!StretchBlt(hdcWindow,
0,0,
rcClient.right, rcClient.bottom,
hdcScreen,
0,0,
GetSystemMetrics (SM_CXSCREEN),
GetSystemMetrics (SM_CYSCREEN),
SRCCOPY))
{
MessageBox(hWnd, L"StretchBlt has failed",L"Failed", MB_OK);
goto done;
}
// Create a compatible bitmap from the Window DC
hbmScreen = CreateCompatibleBitmap(hdcWindow, rcClient.right-rcClient.left, rcClient.bottom-rcClient.top);
if(!hbmScreen)
{
MessageBox(hWnd, L"CreateCompatibleBitmap Failed",L"Failed", MB_OK);
goto done;
}
// Select the compatible bitmap into the compatible memory DC.
SelectObject(hdcMemDC,hbmScreen);
// Bit block transfer into our compatible memory DC.
if(!BitBlt(hdcMemDC,
0,0,
rcClient.right-rcClient.left, rcClient.bottom-rcClient.top,
hdcWindow,
0,0,
SRCCOPY))
{
MessageBox(hWnd, L"BitBlt has failed", L"Failed", MB_OK);
goto done;
}
// Get the BITMAP from the HBITMAP
GetObject(hbmScreen,sizeof(BITMAP),&bmpScreen);
BITMAPFILEHEADER bmfHeader;
BITMAPINFOHEADER bi;
bi.biSize = sizeof(BITMAPINFOHEADER);
bi.biWidth = bmpScreen.bmWidth;
bi.biHeight = bmpScreen.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 = ((bmpScreen.bmWidth * bi.biBitCount + 31) / 32) * 4 * bmpScreen.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(hdcWindow, hbmScreen, 0,
(UINT)bmpScreen.bmHeight,
lpbitmap,
(BITMAPINFO *)&bi, DIB_RGB_COLORS);
// A file is created, this is where we will save the screen capture.
HANDLE hFile = CreateFile(L"captureqwsx.bmp",
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);
//Clean up
done:
DeleteObject(hbmScreen);
DeleteObject(hdcMemDC);
ReleaseDC(NULL,hdcScreen);
ReleaseDC(hWnd,hdcWindow);
return 0;
}

复制代码

跳转到最佳答案楼层

dbjs · 发表于 2020-8-20 11:41:59

从微软拿过来的地址

int CaptureAnImage(HWND hWnd)
{
HDC hdcScreen;
HDC hdcWindow;
HDC hdcMemDC = NULL;
HBITMAP hbmScreen = NULL;
BITMAP bmpScreen;
// Retrieve the handle to a display device context for the client
// area of the window.
hdcScreen = GetDC(NULL);
hdcWindow = GetDC(hWnd);
// Create a compatible DC which is used in a BitBlt from the window DC
hdcMemDC = CreateCompatibleDC(hdcWindow);
if(!hdcMemDC)
{
MessageBox(hWnd, L"CreateCompatibleDC has failed",L"Failed", MB_OK);
goto done;
}
// Get the client area for size calculation
RECT rcClient;
GetClientRect(hWnd, &rcClient);
//This is the best stretch mode
SetStretchBltMode(hdcWindow,HALFTONE);
//The source DC is the entire screen and the destination DC is the current window (HWND)
if(!StretchBlt(hdcWindow,
0,0,
rcClient.right, rcClient.bottom,
hdcScreen,
0,0,
GetSystemMetrics (SM_CXSCREEN),
GetSystemMetrics (SM_CYSCREEN),
SRCCOPY))
{
MessageBox(hWnd, L"StretchBlt has failed",L"Failed", MB_OK);
goto done;
}
// Create a compatible bitmap from the Window DC
hbmScreen = CreateCompatibleBitmap(hdcWindow, rcClient.right-rcClient.left, rcClient.bottom-rcClient.top);
if(!hbmScreen)
{
MessageBox(hWnd, L"CreateCompatibleBitmap Failed",L"Failed", MB_OK);
goto done;
}
// Select the compatible bitmap into the compatible memory DC.
SelectObject(hdcMemDC,hbmScreen);
// Bit block transfer into our compatible memory DC.
if(!BitBlt(hdcMemDC,
0,0,
rcClient.right-rcClient.left, rcClient.bottom-rcClient.top,
hdcWindow,
0,0,
SRCCOPY))
{
MessageBox(hWnd, L"BitBlt has failed", L"Failed", MB_OK);
goto done;
}
// Get the BITMAP from the HBITMAP
GetObject(hbmScreen,sizeof(BITMAP),&bmpScreen);
BITMAPFILEHEADER bmfHeader;
BITMAPINFOHEADER bi;
bi.biSize = sizeof(BITMAPINFOHEADER);
bi.biWidth = bmpScreen.bmWidth;
bi.biHeight = bmpScreen.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 = ((bmpScreen.bmWidth * bi.biBitCount + 31) / 32) * 4 * bmpScreen.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(hdcWindow, hbmScreen, 0,
(UINT)bmpScreen.bmHeight,
lpbitmap,
(BITMAPINFO *)&bi, DIB_RGB_COLORS);
// A file is created, this is where we will save the screen capture.
HANDLE hFile = CreateFile(L"captureqwsx.bmp",
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);
//Clean up
done:
DeleteObject(hbmScreen);
DeleteObject(hdcMemDC);
ReleaseDC(NULL,hdcScreen);
ReleaseDC(hWnd,hdcWindow);
return 0;
}

复制代码

wyxhehe · 发表于 2020-8-20 18:40:45

谢谢！虽然还是不太明白我的代码貌似也没少什么关键的地方吧？

dbjs · 发表于 2020-8-21 12:29:09

试试动态申请内存

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[已解决]关于获取屏幕截图后在内存数据指针的问题

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