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&nbsp;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&nbsp;RGBQUAD// data structures.)if (cClrBits != 24)pbmi = (PBITMAPINFO) LocalAlloc(LPTR,sizeof(BITMAPINFOHEADER) +sizeof(RGBQUAD) * (1<< cClrBits));// There is&nbsp;no&nbsp;RGBQUAD array for the 24-bit-per-pixel format.elsepbmi = (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&nbsp;= bmp.bmBitsPixel;if (cClrBits < 24)pbmi->bmiHeader.biClrUsed = (1<<cClrBits);// If the bitmap is&nbsp;not compressed, set the BI_RGB flag.pbmi->bmiHeader.biCompression = BI_RGB;// Compute the number of&nbsp;bytes in the array of color// indices and store the result in biSizeImage.// For Windows NT, the width must be&nbsp;DWORD&nbsp;aligned unless// the bitmap is&nbsp;RLE&nbsp;compressed. This example shows this.// For Windows 95/98/Me, the width must be WORD aligned unless the// bitmap is&nbsp;RLE&nbsp;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 handleBITMAPFILEHEADER hdr; // bitmap file-headerPBITMAPINFOHEADER pbih; // bitmap info-headerLPBYTE lpBits; // memory pointerDWORD dwTotal; // total count of bytesDWORD cb; // incremental count of bytesBYTE *hp; // byte pointerDWORD 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DCCBitmap *pOldbmp = memDC.SelectObject(&bmp); //将位图加载到内存DCCRect 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DCCBitmap 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 heredc.LineTo(0,0);dc.MoveTo(100,100);// Do not call CFormView::OnPaint() for painting messages}