晕菜!!!GetPixel() 与 GetDIBits()得到的数据不一致!

[aqua2013]

因为GetPixel()读取屏幕的速度实在太慢,所以用GDI的GetDIBits()函数和 BitBlt()函数来获取屏幕像素数据,但是实际使用时发现 对于普通窗口这两种方法都可以获得正确数据,然而对于游戏之类的窗口GetPixel()获得的数据是正确的,GetDIBits()不正常,但奇怪的是我用BitBlt()拷贝数据到我的程序窗口显示也是正确的,仅仅是用GetDIBits()获得的数据不一样,直接读缓冲区的方式都试过了,这个数据就是不一样,然而拿去显示又是正确的.我真是哭了

HDC hDc, hMemDC;
	hDc = CreateDC(_T("DISPLAY"), NULL, NULL, NULL);
	hMemDC = CreateCompatibleDC(hDc);
	
	HBITMAP     hOldBmp, hBitmap;

	hBitmap = CreateCompatibleBitmap(hDc, 62,20);
	hOldBmp = (HBITMAP)SelectObject(hMemDC, hBitmap);
	BitBlt(hMemDC, 0, 0, 62, 20, hDc, 1703, 333, SRCCOPY);
	HDC thdc = GetDC(hwnd);
	BitBlt(thdc, 0, 0, 62, 20, hMemDC, 0, 0, SRCCOPY);
	BitBlt(hMemDC, 0, 0, 62, 20, thdc, 62, 0, SRCCOPY);
	{
		BITMAPINFO bitmapInfo = { 0 };
		bitmapInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
		GetDIBits(hMemDC, hBitmap, 0, 20, NULL, &bitmapInfo, DIB_RGB_COLORS);
		unsigned char* bitmapBits = new unsigned char[bitmapInfo.bmiHeader.biSizeImage];
		memset(bitmapBits, 0, bitmapInfo.bmiHeader.biSizeImage);//初始为0
		//第二次才会有数据
		GetDIBits(hMemDC, hBitmap, 0, 20, bitmapBits, &bitmapInfo, DIB_RGB_COLORS);
		unsigned int rgb = GetPixel(hMemDC, 0, 0);
		delete[]bitmapBits;
	}
	BitBlt(hMemDC, 0, 0, 62, 20, thdc, 0, 0, SRCCOPY);
	ReleaseDC(hwnd, thdc);

//第一次调用 GetDIBits函数，并将参数五置为NULL，且bitmapInfo的BITMAPINFOHEADER结构的biSize已经初始化过,
//函数将会把图像的宽，高还有整个图像所点的字节数填充到bitmapInfo结构中，以便接下来的使用
	BITMAPINFO bitmapInfo = { 0 };
	bitmapInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
	GetDIBits(hMemDC, hBitmap, 0, 20, NULL, &bitmapInfo, DIB_RGB_COLORS);
	unsigned char* bitmapBits = new unsigned char[bitmapInfo.bmiHeader.biSizeImage];
	memset(bitmapBits, 0, bitmapInfo.bmiHeader.biSizeImage);//初始为0
	//第二次才会有数据
	GetDIBits(hMemDC, hBitmap, 0, 20, bitmapBits, &bitmapInfo, DIB_RGB_COLORS);
	unsigned int rgb=GetPixel(hMemDC, 0, 0);

[schlafenhamster]

不是要 取 color 吗？
// Get colors
GetDIBColorTable(hSourceDC, 0, 256, lpbmi->bmiColors);
// Get bits
BYTE *Bits=new BYTE[dwBitsSize];
GetDIBits(hSourceDC,hSrcBmp,0,lpbmi->bmiHeader.biHeight,Bits,lpbmi,DIB_RGB_COLORS);//

[zgl7903]

与DDB不同，DIB的字节数组是从图象的最下面一行开始的逐行向上存储的，也即等于把图象倒过来然后在逐行扫描。另外，字节数组中每个扫描行的字节数必需是4的倍数，如果不足要用0补齐。

[schlafenhamster]

void CVC60Doc::Save8BitBmp(HBITMAP hSrcBmp,char *fileName)
{// hSrcBmp is an 8 bits bmp.
	char defFileName[MAX_PATH];
	strcpy(defFileName,m_fileName);
	char *slashAt=strrchr(defFileName,'\\');
	if(slashAt) *slashAt=0;
	if(hSrcBmp==m_hBmpRight)
	{
		strcat(defFileName,"\\Octree8.bmp");
	}
	else
	{
		strcat(defFileName,"\\Popularty8.bmp");
	}
// bmp info
    BITMAP bmp;
	GetObject(hSrcBmp, sizeof(BITMAP), &bmp);
	bmp.bmWidthBytes = (bmp.bmWidthBytes + 3) & ~3;
	DWORD dwBitsSize = bmp.bmHeight * bmp.bmWidthBytes;// 
//
	DWORD dwHeaderSize = sizeof(BITMAPINFO) + (256 * sizeof(RGBQUAD)); 
    LPBITMAPINFO lpbmi = NULL; 
    lpbmi = (LPBITMAPINFO)malloc(dwBitsSize); 
    lpbmi->bmiHeader.biSize = sizeof(BITMAPINFOHEADER); 
    lpbmi->bmiHeader.biWidth = bmp.bmWidth; 
    lpbmi->bmiHeader.biHeight = bmp.bmHeight; 
    lpbmi->bmiHeader.biPlanes = 1; 
    lpbmi->bmiHeader.biBitCount = 8; 
    lpbmi->bmiHeader.biCompression = BI_RGB; 
    lpbmi->bmiHeader.biSizeImage = 0; 
    lpbmi->bmiHeader.biXPelsPerMeter = 0; 
    lpbmi->bmiHeader.biYPelsPerMeter = 0; 
    lpbmi->bmiHeader.biClrUsed = 256; 
    lpbmi->bmiHeader.biClrImportant = 256; 
    lpbmi->bmiHeader.biSizeImage = dwBitsSize; 
// 
	HDC hDC = GetDC(NULL); 
    HDC hSourceDC = CreateCompatibleDC(hDC); 
// we Select the src Object, for the info
	HBITMAP hOldSourceBitmap = (HBITMAP)SelectObject(hSourceDC,hSrcBmp); 
// Get colors
	GetDIBColorTable(hSourceDC, 0, 256, lpbmi->bmiColors);
// Get bits
	BYTE *Bits=new BYTE[dwBitsSize];
    GetDIBits(hSourceDC,hSrcBmp,0,lpbmi->bmiHeader.biHeight,Bits,lpbmi,DIB_RGB_COLORS);//
// setback
	SelectObject(hSourceDC, hOldSourceBitmap); 
// we have all we need; do saving
	FILE *p1;
	if(fileName)
	{
		strcpy(defFileName,fileName);
	}
	p1 = fopen(defFileName,"wb");
// file head
	BITMAPFILEHEADER headBMP;
	headBMP.bfType='MB';
	headBMP.bfSize=dwBitsSize;
	headBMP.bfOffBits=	sizeof(BITMAPFILEHEADER) +// 14
						sizeof(BITMAPINFOHEADER) +// 40 
						sizeof(RGBQUAD)*256;
	headBMP.bfReserved1=0;
	headBMP.bfReserved2=0;
// file write
	fwrite(&headBMP, 1, sizeof(BITMAPFILEHEADER), p1);//14
	fwrite(lpbmi, 1, sizeof(BITMAPINFOHEADER)+sizeof(RGBQUAD)*256,p1);//40 + 4*256 colors
	fwrite(Bits, 1, dwBitsSize, p1);// Dibs
	fclose(p1);
// free
	delete []Bits;
	DeleteDC(hSourceDC); 
    ReleaseDC(NULL, hDC); 
    free(lpbmi);
//	
	AfxMessageBox(CString("8 Bits BitMap '") + defFileName +"' Saved!");
}

[aqua2013]

已经解决,用GetBitmapBits()函数就可以了