我正在位图中捕获桌面窗口的特定部分并尝试打印 BGR 像素颜色值。捕获的桌面窗口部分完全填充了 16、0、16 色。
当我的窗口颜色深度为 32 时捕获并打印数据时，一切正常，但如果我的窗口处于 24/16 位颜色模式，那么我将获得不同的像素值，而不是 16、0、16。
我正在捕获屏幕左侧 = 150，顶部 = 150，右侧 = 200，底部 = 200。 * ** * ** * **从桌面捕获图像* ** * ** * **
iLeft = 150;
iTop = 150;
iRight = iLeft + 50;
iBottom = iTop + 50;
/*
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;
*/
//#if 0
HDC hdcScreen;
// HDC hdcWindow;
HDC hdcMemDC = NULL;
HBITMAP hbmScreen = NULL;
HRGN rgn = NULL;
BITMAP bmpScreen;
// Retrieve the handle to a display device context for the client
// area of the window.
hdcScreen = GetDC(NULL);
//hdcWindow = GetDC(hWnd);
//if(g_hdcMemDC == NULL)
{
// Create a compatible DC which is used in a BitBlt from the window DC
hdcMemDC = CreateCompatibleDC(hdcScreen);
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(hdcMemDC,HALFTONE);
// Create a compatible bitmap from the Window DC
hbmScreen = CreateCompatibleBitmap(hdcScreen, iRight - iLeft, iBottom - iTop);
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);
}
//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;
}
*/
// Bit block transfer into our compatible memory DC.
if(!StretchBlt(hdcMemDC,
0,0,
iRight - iLeft,
iBottom - iTop,
hdcScreen,
iLeft,iTop,
iRight - iLeft,
iBottom - iTop,
SRCCOPY))
{
// MessageBox(hWnd, L"StretchBlt has failed",L"Failed", MB_OK);
goto done;
}
}
*******************FUNCTION FOR GETTING THE BITMAP RAW DATA POINTER***********
BYTE* Get24BitPixels(HDC dcDesktop, HBITMAP pBitmap, WORD *pwWidth, WORD *pwHeight, WORD * pReminderWidth)
{
// a bitmap object just to get bitmap width and height
BITMAP bmpBmp;
// pointer to original bitmap info
LPBITMAPINFO pbmiInfo;
// bitmap info will hold the new 24bit bitmap info
BITMAPINFO bmiInfo;
// width and height of the bitmap
WORD wBmpWidth ; WORD wBmpHeight;
// ---------------------------------------------------------
// get some info from the bitmap
// ---------------------------------------------------------
GetObject(pBitmap, sizeof(bmpBmp),&bmpBmp);
pbmiInfo = (LPBITMAPINFO)&bmpBmp;
//get width and height
wBmpWidth = (WORD)pbmiInfo->bmiHeader.biWidth;
int iReminderWidth = (wBmpWidth%4);
//wBmpWidth -= (wBmpWidth%4); // width is 4 byte boundary aligned.
wBmpHeight = (WORD)pbmiInfo->bmiHeader.biHeight;
// copy to caller width and height parms
*pwWidth = wBmpWidth;
*pwHeight = wBmpHeight;
wBmpWidth += (4 - iReminderWidth); // width is 4 byte boundary aligned, thereby increasing the width
//so that it will be fully divible by four , it will cause some extra bytes to be filled in with garbage value
//beyond the actual width of the bitmap, we will be discrading this extra padding pixels data while processign each pixel.
*pReminderWidth = 4 - iReminderWidth;
// ---------------------------------------------------------
// allocate width * height * 24bits pixels
BYTE * pPixels = new BYTE[wBmpWidth*wBmpHeight*3];
if (!pPixels) return NULL;
// get user desktop device context to get pixels from
//HDC hDC = GetWindowDC(NULL);
// fill desired structure
bmiInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bmiInfo.bmiHeader.biWidth = wBmpWidth;
bmiInfo.bmiHeader.biHeight = -wBmpHeight;
bmiInfo.bmiHeader.biPlanes = 1;
bmiInfo.bmiHeader.biBitCount = 24;
bmiInfo.bmiHeader.biCompression = BI_RGB;
bmiInfo.bmiHeader.biSizeImage = wBmpWidth*wBmpHeight*3;
bmiInfo.bmiHeader.biXPelsPerMeter = 0;
bmiInfo.bmiHeader.biYPelsPerMeter = 0;
bmiInfo.bmiHeader.biClrUsed = 0;
bmiInfo.bmiHeader.biClrImportant = 0;
// get pixels from the original bitmap converted to 24bits
int iRes = GetDIBits(dcDesktop,pBitmap,0,wBmpHeight,(LPVOID)pPixels,&bmiInfo,DIB_RGB_COLORS);
// release the device context
//ReleaseDC(NULL,hDC);
// if failed, cancel the operation.
if (!iRes)
{
delete [] pPixels;
pPixels = NULL;
return NULL;
};
// return the pixel array
return pPixels;
}