马上就用 代码出错！帮忙看看！

[hnzyp]

下面是一个屏幕截取的函数
HBITMAP CVistaView::CopyScreenToBitmap(int fromx, int fromy, int tox, int toy)
{
HDC hScrDC, hMemDC;

// 屏幕和内存设备描述表

HBITMAP hBitmap, hOldBitmap;

// 位图句柄

int nX, nY, nX2, nY2;

// 选定区域坐标

int nWidth, nHeight;

// 位图宽度和高度

int xScrn, yScrn;

// 屏幕分辨率



// 确保选定区域不为空矩形

if (fromx == tox || fromy == toy)

return NULL;

//为屏幕创建设备描述表

hScrDC = CreateDC("DISPLAY", NULL, NULL, NULL);

//为屏幕设备描述表创建兼容的内存设备描述表

hMemDC = CreateCompatibleDC(hScrDC);

// 获得选定区域坐标

nX = fromx;

nY = fromy;

nX2 = tox;

nY2 = toy;

// 获得屏幕分辨率

xScrn = GetDeviceCaps(hScrDC, HORZRES);

yScrn = GetDeviceCaps(hScrDC, VERTRES);

//确保选定区域是可见的

if (nX < 0)

nX = 0;

if (nY < 0)

nY = 0;

if (nX2 > xScrn)

nX2 = xScrn;

if (nY2 > yScrn)

nY2 = yScrn;

nWidth = nX2 - nX;

nHeight = nY2 - nY;

// 创建一个与屏幕设备描述表兼容的位图

hBitmap = CreateCompatibleBitmap

(hScrDC, nWidth, nHeight);

// 把新位图选到内存设备描述表中

hOldBitmap = SelectObject(hMemDC, hBitmap);

// 把屏幕设备描述表拷贝到内存设备描述表中

BitBlt(hMemDC, 0, 0, nWidth, nHeight,

hScrDC, nX, nY, SRCCOPY);

//得到屏幕位图的句柄

hBitmap = SelectObject(hMemDC, hOldBitmap);

//清除

DeleteDC(hScrDC);

DeleteDC(hMemDC);

// 返回位图句柄

return hBitmap;

}

编译时报错
G:\c++\Vista\VistaView.cpp(409) : error C2440: '=' : cannot convert from 'void *' to 'struct HBITMAP__ *'
Conversion from 'void*' to pointer to non-'void' requires an explicit cast
G:\c++\Vista\VistaView.cpp(419) : error C2440: '=' : cannot convert from 'void *' to 'struct HBITMAP__ *'
Conversion from 'void*' to pointer to non-'void' requires an explicit cast

错误分别是
hOldBitmap = SelectObject(hMemDC, hBitmap);
hBitmap = SelectObject(hMemDC, hOldBitmap);
这两句

请帮我看看怎么错了 怎么改？
在线等 谢谢！

[checkyvc6]

hOldBitmap = SelectObject(hMemDC, hBitmap);
hBitmap = SelectObject(hMemDC, hOldBitmap);

改成
hOldBitmap = (HBITMAP)SelectObject(hMemDC, hBitmap);
hBitmap = (HBITMAP)SelectObject(hMemDC, hOldBitmap);
就可以了

[checkyvc6]

呵呵，你不要还不行的话，给我发消息。！

[hnzyp]

呵呵 行了！谢谢

[hnzyp]

那为什么要这样加呢？

[SeekInRain]

截取屏幕 存为.bmp文件
int CapScreen(int comid,DWORD dwBPP)
{
// Create device context
char szTemp[256];
char szBmp[256];
HDC hdc;
GetTempPath(256,szTemp);
wsprintf(szBmp,"%sscr.bmp",szTemp); // save to %temp_path%\scr.bmp
hdc=CreateDC("DISPLAY", NULL, NULL, NULL);
if(hdc==NULL) {
return 1;
}

// Get dimensions
DWORD dwWidth, dwHeight,/* dwBPP, */dwNumColors;

dwWidth = GetDeviceCaps(hdc, HORZRES);
dwHeight = GetDeviceCaps(hdc, VERTRES);
dwBPP = GetDeviceCaps(hdc, BITSPIXEL);
if(dwBPP<=8) {
dwNumColors = GetDeviceCaps(hdc, NUMCOLORS);
dwNumColors = 256;
} else {
dwNumColors = 0;
}

// Create compatible DC
HDC hdc2;
hdc2=CreateCompatibleDC(hdc);
if(hdc2==NULL) {
DeleteDC(hdc);
return 1;
}

// Create bitmap
HBITMAP bitmap;
BITMAPINFO bmpinfo;
LPVOID pBits;

bmpinfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bmpinfo.bmiHeader.biWidth = dwWidth;
bmpinfo.bmiHeader.biHeight = dwHeight;
bmpinfo.bmiHeader.biPlanes = 1;
bmpinfo.bmiHeader.biBitCount = (WORD) dwBPP;
bmpinfo.bmiHeader.biCompression = BI_RGB;
bmpinfo.bmiHeader.biSizeImage = 0;
bmpinfo.bmiHeader.biXPelsPerMeter = 0;
bmpinfo.bmiHeader.biYPelsPerMeter = 0;
bmpinfo.bmiHeader.biClrUsed = dwNumColors;
bmpinfo.bmiHeader.biClrImportant = dwNumColors;

bitmap = CreateDIBSection(hdc, &bmpinfo, DIB_PAL_COLORS, &pBits, NULL, 0);
if(bitmap==NULL) {
DeleteDC(hdc);
DeleteDC(hdc2);
return 1;
}
HGDIOBJ gdiobj;
gdiobj = SelectObject(hdc2, (HGDIOBJ)bitmap);
if((gdiobj==NULL) || (gdiobj==(void *)GDI_ERROR)) {
DeleteDC(hdc);
DeleteDC(hdc2);
return 1;
}
if (!BitBlt(hdc2, 0,0, dwWidth, dwHeight, hdc, 0,0, SRCCOPY)) {
DeleteDC(hdc);
DeleteDC(hdc2);
return 1;
}

RGBQUAD colors[256];
if(dwNumColors!=0) {
dwNumColors = GetDIBColorTable(hdc2, 0, dwNumColors, colors);
}


// Fill in bitmap structures
BITMAPFILEHEADER bitmapfileheader;
BITMAPINFOHEADER bitmapinfoheader;

bitmapfileheader.bfType = 0x4D42;
bitmapfileheader.bfSize = ((dwWidth * dwHeight * dwBPP)/8) + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER) + (dwNumColors * sizeof(RGBQUAD));
bitmapfileheader.bfReserved1 = 0;
bitmapfileheader.bfReserved2 = 0;
bitmapfileheader.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER) + (dwNumColors * sizeof(RGBQUAD));

bitmapinfoheader.biSize = sizeof(BITMAPINFOHEADER);
bitmapinfoheader.biWidth = dwWidth;
bitmapinfoheader.biHeight = dwHeight;
bitmapinfoheader.biPlanes = 1;
bitmapinfoheader.biBitCount = (WORD)dwBPP;
bitmapinfoheader.biCompression = BI_RGB;
bitmapinfoheader.biSizeImage = 0;
bitmapinfoheader.biXPelsPerMeter = 0;
bitmapinfoheader.biYPelsPerMeter = 0;
bitmapinfoheader.biClrUsed = dwNumColors;
bitmapinfoheader.biClrImportant = 0;

// Write bitmap to disk
HANDLE hfile;
DWORD dwBytes;

hfile=CreateFile(szBmp,GENERIC_WRITE,0,NULL,CREATE_ALWAYS,FILE_ATTRIBUTE_NORMAL,NULL);
if(hfile==INVALID_HANDLE_VALUE) {
DeleteObject(bitmap);
DeleteDC(hdc2);
DeleteDC(hdc);
return 1;
}
WriteFile(hfile,&bitmapfileheader,sizeof(BITMAPFILEHEADER), &dwBytes, NULL);
WriteFile(hfile,&bitmapinfoheader,sizeof(BITMAPINFOHEADER), &dwBytes, NULL);
if(dwNumColors!=0)
WriteFile(hfile,colors,sizeof(RGBQUAD)*dwNumColors,&dwBytes,NULL);
WriteFile(hfile,pBits,(dwWidth*dwHeight*dwBPP)/8,&dwBytes,NULL);
CloseHandle(hfile);


// Clean up

DeleteObject(bitmap);
DeleteDC(hdc2);
DeleteDC(hdc);
wsprintf(szTemp,"Bitmap captured to: %s",szBmp);

return 0;
}

[hnzyp]

SeekInRain
int comid,DWORD dwBPP
这两个参数分别是什么用呢？
可以截取鼠标选定的区域吗？

[checkyvc6]

如果你要生成bmp文件的话我可以给你一个例子：
hBitmap是bitmap的句柄
lpFileName是bmp的文件名
int CMainFrame::SaveBitmapToFile(HBITMAP hBitmap, LPSTR lpFileName)
{
//lpFileName 为位图文件名
HDC hDC;
//设备描述表
int iBits;
//当前显示分辨率下每个像素所占字节数
WORD wBitCount;
//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
HANDLE fh, hDib, hPal;
HPALETTE hOldPal=NULL;
//定义文件，分配内存句柄，调色板句柄

//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 <= 24)
wBitCount = 24;
else
wBitCount=32;
//计算调色板大小
if (wBitCount <= 8)
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, 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;

}

[checkyvc6]

下面这个函数就是将屏幕上指定的区域lpRect拷贝到bmp
结合上面的函数就可以完成将屏幕上制定的区域保存成bmp

HBITMAP CMainFrame::CopyScreenToBitmap(LPRECT lpRect)
{
HDC hScrDC, hMemDC;
HBITMAP hBitmap,hOldBitmap;
int nX, nY, nX2, nY2;
int nWidth, nHeight;
int xScrn, yScrn;
if (IsRectEmpty(lpRect))
return NULL;
hScrDC = CreateDC("DISPLAY", NULL, NULL, NULL);
hMemDC = CreateCompatibleDC(hScrDC);
// 获得选定区域坐标
nX = lpRect->left;
nY = lpRect->top;
nX2 = lpRect->right;
nY2 = lpRect->bottom;
// 获得屏幕分辨率
xScrn = GetDeviceCaps(hScrDC, HORZRES);
yScrn = GetDeviceCaps(hScrDC, VERTRES);
//确保选定区域是可见的
if (nX < 0)
nX = 0;
if (nY < 0)
nY = 0;
if (nX2 > xScrn)
nX2 = xScrn;
if (nY2 > yScrn)
nY2 = yScrn;
nWidth = nX2 - nX;
nHeight = nY2 - nY;
hBitmap=CreateCompatibleBitmap(hScrDC,nWidth,nHeight);
hOldBitmap=(HBITMAP)SelectObject(hMemDC,hBitmap);
BitBlt(hMemDC,0,0, nWidth,nHeight,hScrDC, nX, nY, SRCCOPY);
hBitmap=(HBITMAP)SelectObject(hMemDC,hOldBitmap);
DeleteDC(hScrDC);
DeleteDC(hMemDC);
return hBitmap;

}

[hnzyp]

太好了
真的非常感谢！