怎样才能用VC的onpaint函数在位图上画点和线呢？

Question

怎样才能用VC的onpaint函数在位图上画点和线呢？

Answer 1

下面的代码转自MSDN，"Storing an Image"
// 获取HBITMAP的位图信息
PBITMAPINFO CreateBitmapInfoStruct(HWND hwnd, HBITMAP hBmp)
{
BITMAP bmp;
PBITMAPINFO pbmi;
WORD cClrBits;

// Retrieve the bitmap color format, width, and height.
if (!GetObject(hBmp, sizeof(BITMAP), (LPSTR)&bmp))
errhandler("GetObject", hwnd);

// Convert the color format to a count of bits.
cClrBits = (WORD)(bmp.bmPlanes * bmp.bmBitsPixel);
if (cClrBits == 1)
cClrBits = 1;
else if (cClrBits <= 4)
cClrBits = 4;
else if (cClrBits <= 8)
cClrBits = 8;
else if (cClrBits <= 16)
cClrBits = 16;
else if (cClrBits <= 24)
cClrBits = 24;
else cClrBits = 32;

// Allocate memory for the BITMAPINFO structure. (This structure
// contains a BITMAPINFOHEADER structure and an array of RGBQUAD
// data structures.)

if (cClrBits != 24)
pbmi = (PBITMAPINFO) LocalAlloc(LPTR,
sizeof(BITMAPINFOHEADER) +
sizeof(RGBQUAD) * (1<< cClrBits));

// There is no RGBQUAD array for the 24-bit-per-pixel format.

else
pbmi = (PBITMAPINFO) LocalAlloc(LPTR,
sizeof(BITMAPINFOHEADER));

// Initialize the fields in the BITMAPINFO structure.

pbmi->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
pbmi->bmiHeader.biWidth = bmp.bmWidth;
pbmi->bmiHeader.biHeight = bmp.bmHeight;
pbmi->bmiHeader.biPlanes = bmp.bmPlanes;
pbmi->bmiHeader.biBitCount = bmp.bmBitsPixel;
if (cClrBits < 24)
pbmi->bmiHeader.biClrUsed = (1<<cClrBits);

// If the bitmap is not compressed, set the BI_RGB flag.
pbmi->bmiHeader.biCompression = BI_RGB;

// Compute the number of bytes in the array of color
// indices and store the result in biSizeImage.
// For Windows NT, the width must be DWORD aligned unless
// the bitmap is RLE compressed. This example shows this.
// For Windows 95/98/Me, the width must be WORD aligned unless the
// bitmap is RLE compressed.
pbmi->bmiHeader.biSizeImage = ((pbmi->bmiHeader.biWidth * cClrBits +31) & ~31) /8
* pbmi->bmiHeader.biHeight;
// Set biClrImportant to 0, indicating that all of the
// device colors are important.
pbmi->bmiHeader.biClrImportant = 0;
return pbmi;
}
//将HBITMAP保存到文件
void CreateBMPFile(HWND hwnd, LPTSTR pszFile, PBITMAPINFO pbi,
HBITMAP hBMP, HDC hDC)
{
HANDLE hf; // file handle
BITMAPFILEHEADER hdr; // bitmap file-header
PBITMAPINFOHEADER pbih; // bitmap info-header
LPBYTE lpBits; // memory pointer
DWORD dwTotal; // total count of bytes
DWORD cb; // incremental count of bytes
BYTE *hp; // byte pointer
DWORD dwTmp;

pbih = (PBITMAPINFOHEADER) pbi;
lpBits = (LPBYTE) GlobalAlloc(GMEM_FIXED, pbih->biSizeImage);

if (!lpBits)
errhandler("GlobalAlloc", hwnd);

// Retrieve the color table (RGBQUAD array) and the bits
// (array of palette indices) from the DIB.
if (!GetDIBits(hDC, hBMP, 0, (WORD) pbih->biHeight, lpBits, pbi,
DIB_RGB_COLORS))
{
errhandler("GetDIBits", hwnd);
}

// Create the .BMP file.
hf = CreateFile(pszFile,
GENERIC_READ | GENERIC_WRITE,
(DWORD) 0,
NULL,
CREATE_ALWAYS,
FILE_ATTRIBUTE_NORMAL,
(HANDLE) NULL);
if (hf == INVALID_HANDLE_VALUE)
errhandler("CreateFile", hwnd);
hdr.bfType = 0x4d42; // 0x42 = "B" 0x4d = "M"
// Compute the size of the entire file.
hdr.bfSize = (DWORD) (sizeof(BITMAPFILEHEADER) +
pbih->biSize + pbih->biClrUsed
* sizeof(RGBQUAD) + pbih->biSizeImage);
hdr.bfReserved1 = 0;
hdr.bfReserved2 = 0;

// Compute the offset to the array of color indices.
hdr.bfOffBits = (DWORD) sizeof(BITMAPFILEHEADER) +
pbih->biSize + pbih->biClrUsed
* sizeof (RGBQUAD);

// Copy the BITMAPFILEHEADER into the .BMP file.
if (!WriteFile(hf, (LPVOID) &hdr, sizeof(BITMAPFILEHEADER),
(LPDWORD) &dwTmp, NULL))
{
errhandler("WriteFile", hwnd);
}

// Copy the BITMAPINFOHEADER and RGBQUAD array into the file.
if (!WriteFile(hf, (LPVOID) pbih, sizeof(BITMAPINFOHEADER)
+ pbih->biClrUsed * sizeof (RGBQUAD),
(LPDWORD) &dwTmp, ( NULL)))
errhandler("WriteFile", hwnd);

// Copy the array of color indices into the .BMP file.
dwTotal = cb = pbih->biSizeImage;
hp = lpBits;
if (!WriteFile(hf, (LPSTR) hp, (int) cb, (LPDWORD) &dwTmp,NULL))
errhandler("WriteFile", hwnd);

// Close the .BMP file.
if (!CloseHandle(hf))
errhandler("CloseHandle", hwnd);

// Free memory.
GlobalFree((HGLOBAL)lpBits);
}
-------
改变位图，就是把位图加载到设备上，然后绘图，最后把设备位图重新保存。
LZ想怎么改变位图？
-------
修改位图补完版：
在应用程序的OnPaint里添加如下代码，将位图绘制出来
void Cxxx::OnPaint()
{
CBitmap bmp;
if(bmp.Attach((HBITMAP)::LoadImage(AfxGetApp()->m_hInstance, _T(".\\bmptest.bmp"), IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE))) //从文件加载位图，这个应该放到程序初始化里面，将bmp作为成员变量避免重复加载，但是我懒得写那么多了
{
CPaintDC dc(this);
CDC memDC;
memDC.CreateCompatibleDC(&dc);//创建内存DC
CBitmap *pOldbmp = memDC.SelectObject(&bmp); //将位图加载到内存DC
CRect rc;
GetClientRect(rc);//获取客户区大小，如果需要画整个位图，可以根据需要修改
dc.BitBlt(0, 0, rc.Width(), rc.Height(), &memDC, 0, 0, SRCCOPY);//将位图绘制到窗口上
dc.SetPixel(10, 10, RGB(0, 0, 255)); //在指定的位置画一个蓝色的点
memDC.SelectObject(pOldbmp);//释放
}
}
在任意一个命令里写下如下操作代码保存位图
void Cxxx::OnCommandXXXX()
{
CClientDC dc(this);

CRect rcClient;
GetClientRect(rcClient);//取客户区大小

CDC memDC;
memDC.CreateCompatibleDC(&dc);//创建内存DC
CBitmap bmp;
bmp.CreateCompatibleBitmap(&dc, rcClient.Width(), rcClient.Height());//创建内存位图，大小刚好可以放下客户区内容，这里根据需要修改

CBitmap *pOldBmp = memDC.SelectObject(&bmp);
memDC.BitBlt(0, 0, rcClient.Width(), rcClient.Height(), &dc, 0, 0, SRCCOPY);//将窗口内容画到内存位图上

//这里使用上面给出的两个函数来保存位图到文件当中
PBITMAPINFO pbmi = CreateBitmapInfoStruct(GetSafeHwnd(), bmp);//建立位图信息
CreateBMPFile(GetSafeHwnd(), _T(".\\bmptest.bmp"), pbmi, bmp, memDC);//保存位图到文件
LocalFree(pbmi);//由于pbmi由创建函数分配空间，需要调用者来释放
memDC.SelectObject(pOldBmp);//释放内存位图
}

Answer 2

::OnPaint()
{
CPaintDC dc(this); // device context for painting

// TODO: Add your message handler code here

dc.LineTo(0,0);
dc.MoveTo(100,100);
// Do not call CFormView::OnPaint() for painting messages
}