##请教一个抓图的问题## 200分！！在线等

[hwonzor]

我的程序是一个画图程序，类似Drawcli。现在我想把view的客户区显示的一部分图元（保存在m_ShapeList表中）保存到Cbitmap。我是这样做的，大致代码如下：

//创建兼容DC

CView *pView = GetActiveView();
if ((pView == NULL) || (!::IsWindow(pView->m_hWnd)))
return NULL;
CDC* pDC = pView->GetDC();
CDC memDC;
memDC.CreateCompatibleDC(pDC);

//在内存DC中画图元

POSITION pos = m_ShapeList.GetHeadPosition();
while (pos != NULL)
{
CDrawShape* pShape = m_ShapeList.GetNext(pos);
pShape->OnDraw(&memDC);
}


//创建兼容位图并返回

if (pBmp->CreateCompatibleBitmap(&memDC, 800, 600))
{
CDC dc;
dc.CreateCompatibleDC(&memDC);
CBitmap* pOldBmp = dc.SelectObject(pBmp);
BITMAP bm;
pBmp->GetBitmap(&bm);
dc.StretchBlt(0, 0, 800, 600,
&memDC, 0, 0 , bm.bmWidth, bm.bmHeight, SRCCOPY);
pBmp = dc.SelectObject(pOldBmp);
return pBmp;
}
else
return NULL;

结果返回的bitmap没有像素位。问题出在什么地方？请大侠指教，不胜感激！

[taianmonkey]

HANDLE DDBToDIB(CBitmap &bitmap, DWORD dwCompression,
CPalette *pPal)
{

BITMAP bm;
BITMAPINFOHEADER bi;
LPBITMAPINFOHEADER lpbi;
DWORD dwLen;
HANDLE hDIB;
HANDLE handle;
HDC hDC;
HPALETTE hPal;


ASSERT( bitmap.GetSafeHandle() );

// The function has no arg for bitfields
if( dwCompression == BI_BITFIELDS )
return NULL;

// If a palette has not been supplied, use default palette
hPal = (HPALETTE) pPal->GetSafeHandle();
if (hPal==NULL)
hPal = (HPALETTE) GetStockObject(DEFAULT_PALETTE);

// Get bitmap information
bitmap.GetObject(sizeof(bm),(LPSTR)&bm);

// Initialize the bitmap infoheader
bi.biSize = sizeof(BITMAPINFOHEADER);
bi.biWidth = bm.bmWidth;
bi.biHeight = bm.bmHeight;
bi.biPlanes = 1;
bi.biBitCount = bm.bmPlanes * bm.bmBitsPixel;
//bm.bmPlanes * bm.bmBitsPixel;
bi.biCompression = dwCompression;
bi.biSizeImage = 0;
bi.biXPelsPerMeter = 0;
bi.biYPelsPerMeter = 0;
bi.biClrUsed = 0;
bi.biClrImportant = 0;

// Compute the size of the infoheader and the color table
int nColors = (1 << bi.biBitCount);
if( nColors > 256 )
nColors = 0;
dwLen = bi.biSize + nColors * sizeof(RGBQUAD);

// We need a device context to get the DIB from
hDC = ::GetDC(NULL);
hPal = SelectPalette(hDC,hPal,FALSE);
RealizePalette(hDC);

// Allocate enough memory to hold bitmap infoheader and
// color table
hDIB = GlobalAlloc(GMEM_FIXED,dwLen);

if (!hDIB){
SelectPalette(hDC,hPal,FALSE);
::ReleaseDC(NULL,hDC);
return NULL;
}

lpbi = (LPBITMAPINFOHEADER)hDIB;

*lpbi = bi;

// Call GetDIBits with a NULL lpBits param, so the device
// driver will calculate the biSizeImage field
GetDIBits(hDC, (HBITMAP)bitmap.GetSafeHandle(), 0L,
(DWORD)bi.biHeight,
(LPBYTE)NULL, (LPBITMAPINFO)lpbi,
(DWORD)DIB_RGB_COLORS);

bi = *lpbi;

// If the driver did not fill in the biSizeImage field, then
// compute it
// Each scan line of the image is aligned on a DWORD (32bit)
// boundary
if (bi.biSizeImage == 0){
bi.biSizeImage = ((((bi.biWidth * bi.biBitCount) + 31)
& ~31) / 8) * bi.biHeight;

// If a compression scheme is used, the result may in fact
// be larger
// Increase the size to account for this.
if (dwCompression != BI_RGB)
bi.biSizeImage = (bi.biSizeImage * 3) / 2;
}

// Realloc the buffer so that it can hold all the bits
dwLen += bi.biSizeImage;
if (handle = GlobalReAlloc(hDIB, dwLen, GMEM_MOVEABLE))
hDIB = handle;
else{
GlobalFree(hDIB);

// Reselect the original palette
SelectPalette(hDC,hPal,FALSE);
::ReleaseDC(NULL,hDC);
return NULL;
}

// Get the bitmap bits
lpbi = (LPBITMAPINFOHEADER)hDIB;

// FINALLY get the DIB
BOOL bGotBits = GetDIBits( hDC, (HBITMAP)bitmap.GetSafeHandle(),
0L, // Start scan line
(DWORD)bi.biHeight, // # of scan lines
(LPBYTE)lpbi // address for bitmap bits
+ (bi.biSize + nColors * sizeof(RGBQUAD)),
(LPBITMAPINFO)lpbi, // address of bitmapinfo
(DWORD)DIB_RGB_COLORS); // Use RGB for color table

if( !bGotBits )
{
GlobalFree(hDIB);

SelectPalette(hDC,hPal,FALSE);
::ReleaseDC(NULL,hDC);
return NULL;
}

SelectPalette(hDC,hPal,FALSE);
::ReleaseDC(NULL,hDC);

return hDIB;

//End of the function
}

[taianmonkey]

BOOL CDlg::Tofile(HBITMAP hbitmap, LPSTR lpfilename)
{
HDC hdc; //设备描述表
int ibits;
WORD wbitcount; //当前显示分辨率下每个像素所占字节数

//位图中每个像素所占字节数，定义调色板大小，位图中像素字节大小，位图文件大小 ，写入文件字节数
DWORD dwpalettesize=0, dwbmbitssize, dwdibsize, dwwritten;

BITMAP bitmap; //位图属性结构
BITMAPFILEHEADER bmfhdr; //位图文件头结构
BITMAPINFOHEADER bi; //位图信息头结构
LPBITMAPINFOHEADER lpbi; //指向位图信息头结构

//定义文件，分配内存句柄，调色板句柄
HANDLE fh, hdib, hpal,holdpal=NULL;

//计算位图文件每个像素所占字节数
hdc = CreateDC("display",NULL,NULL,NULL);
ibits = GetDeviceCaps(hdc, BITSPIXEL) * GetDeviceCaps(hdc, PLANES);
DeleteDC(hdc);

if (ibits <= 1)
wbitcount = 1;
else if (ibits <= 4)
wbitcount = 4;
else if (ibits <= 8)
wbitcount = 8;
else if (ibits <= 16)
wbitcount = 16;
else if (ibits <= 24)
wbitcount = 24;
else
wbitcount = 32;

//计算调色板大小
if (wbitcount <= 8)//小于八位按八位处理
dwpalettesize = (1 << wbitcount) * sizeof(RGBQUAD);

//设置位图信息头结构
GetObject(hbitmap, sizeof(BITMAP), (LPSTR)&bitmap);
bi.biSize = sizeof(BITMAPINFOHEADER);
bi.biWidth = bitmap.bmWidth;
bi.biHeight = bitmap.bmHeight;
bi.biPlanes = 1;
bi.biBitCount = wbitcount;
bi.biCompression = BI_RGB;
bi.biSizeImage = 0;
bi.biXPelsPerMeter = 0;
bi.biYPelsPerMeter = 0;
bi.biClrUsed = 0;
bi.biClrImportant = 0;

dwbmbitssize = ((bitmap.bmWidth * wbitcount+31)/32)* 4 * bitmap.bmHeight ;
//为位图内容分配内存
hdib = GlobalAlloc(GHND,dwbmbitssize + dwpalettesize +
sizeof(BITMAPINFOHEADER));
lpbi = (LPBITMAPINFOHEADER)GlobalLock(hdib);
*lpbi = bi;

// 处理调色板
hpal = GetStockObject(DEFAULT_PALETTE);
if (hpal)
{
hdc = ::GetDC(NULL);
holdpal = SelectPalette(hdc, (HPALETTE)hpal, FALSE);
RealizePalette(hdc);
}

// 获取该调色板下新的像素值
GetDIBits(hdc, hbitmap, 0, (UINT) bitmap.bmHeight,(LPSTR)lpbi +
sizeof(BITMAPINFOHEADER)+dwpalettesize,(BITMAPINFO*)lpbi, DIB_RGB_COLORS);

//恢复调色板
if (holdpal)
{
SelectPalette(hdc, (HPALETTE)holdpal, TRUE);
RealizePalette(hdc);
::ReleaseDC(NULL, hdc);
}

//创建位图文件
fh = CreateFile(lpfilename, GENERIC_WRITE, 0, NULL,
CREATE_ALWAYS,FILE_ATTRIBUTE_NORMAL|
FILE_FLAG_SEQUENTIAL_SCAN, NULL);
if (fh == INVALID_HANDLE_VALUE)
return FALSE;

// 设置位图文件头
bmfhdr.bfType = 0x4d42; // "bm"
dwdibsize = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER)+dwpalettesize + dwbmbitssize;
bmfhdr.bfSize = dwdibsize;
bmfhdr.bfReserved1 = 0;
bmfhdr.bfReserved2 = 0;
bmfhdr.bfOffBits = (DWORD)sizeof(BITMAPFILEHEADER) + (DWORD)sizeof(BITMAPINFOHEADER)+ dwpalettesize;

// 写入位图文件头
WriteFile(fh, (LPSTR)&bmfhdr, sizeof(BITMAPFILEHEADER), &dwwritten, NULL);

// 写入位图文件其余内容
WriteFile(fh, (LPSTR)lpbi, dwdibsize, &dwwritten, NULL);
//清除
GlobalUnlock(hdib);
GlobalFree(hdib);
CloseHandle(fh);
return TRUE;
}

[hwonzor]

taianmonkey，我不是要保存文件的意思。

[蒋晟]

http://expert.csdn.net/Expert/topic/2481/2481697.xml

[imlmm]

我觉得可能是应该先创建位图，并选入memDC 然后再调用

dc.CreateCompatibleDC(&memDC);
CBitmap* pOldBmp = dc.SelectObject(pBmp);

while (pos != NULL)
{
CDrawShape* pShape = m_ShapeList.GetNext(pos);
pShape->OnDraw(&memDC);
}

[lambochan]

CView *pView = GetActiveView();
if ((pView == NULL) || (!::IsWindow(pView->m_hWnd)))
return NULL;
CDC* pDC = pView->GetDC();
CDC memDC;
memDC.CreateCompatibleDC(pDC);
//?memDC中有Compatible的Bitmap了？
//在内存DC中画图元

POSITION pos = m_ShapeList.GetHeadPosition();
while (pos != NULL)
{
CDrawShape* pShape = m_ShapeList.GetNext(pos);
pShape->OnDraw(&memDC);
}


//创建兼容位图并返回

if (pBmp->CreateCompatibleBitmap(pDC, 800, 600))//改为pDC试试
{
CDC dc;
dc.CreateCompatibleDC(pDC);//改为pDC试试
CBitmap* pOldBmp = dc.SelectObject(pBmp);
BITMAP bm;
pBmp->GetBitmap(&bm);
dc.StretchBlt(0, 0, 800, 600,
&memDC, 0, 0 , bm.bmWidth, bm.bmHeight, SRCCOPY);
pBmp = dc.SelectObject(pOldBmp);
return pBmp;
}
else
return NULL;

[hdslah]

up

[constantine]

up

[wqs6]

你可以直接调用window的API函数
http://www.ccw.com.cn/htm/produ/special/vc/jiqiao/01_9_13_16.asp

参数设置参考
http://vbworld.sxnw.gov.cn/vbapi/detail/graph2.htm

[GSK168]

现在一回答问题就是代码上,浩浩荡荡，连绵不绝，流行啊，学习

[taianmonkey]

不好意思，没仔细看：
http://expert.csdn.net/Expert/topic/2369/2369056.xml?temp=.7972528

[icedot]

hehe .我也来。

我看楼上的各位再答别人问题时候，好像没有看题目哦。

[changlele]

啊.来完了,一不小心就叫人家抢先了,不知道能否散点分给我,楼主自己解决的吗?

[free_card]

恭喜

[hwonzor]

多谢大家，问题解决了
主要是没搞清楚CreateCompatibleDC和CreateCompatibleBitmap的含义。

[bluebohe]

问题不难，可是没来得及回答
所以蹭分

[changlele]

楼主问这个问题要做什么呢。不会是抓屏吧。我有个抓取屏幕的源代码，好久以前写的。是利用Direct Draw编写的。楼主要是有兴趣，给我一个邮箱地址，或者给我信息，我发给你。不知道
能不能在此蹭点分。快变成4角了，努力赚取点分，不过分吧

[Leemaasn]

我也Up一下

我也Up两下

！！！
^@^

[hwonzor]

我怎么还没结贴啊，对不起了，各位，来者有分！ changlele(梦幻水晶)，把你的代码发到我信箱吧，[e-mail]