给出坐标,裁切图象

Question

我想做一个程序,先给出想要裁切的图象区域的四个点的坐标,然后将坐标植范围内的区域的图象裁切下来,并保存下来.我想问以下大家该怎么做啊,谢谢.

Answer 1

一段截屏保存的代码，可以参考一下，原理是一样void CCatchScreenDlg::OnBnClickedBtnFullscreen()
{
// TODO: 在此添加控件通知处理程序代码
HWND hWnd = ::GetDesktopWindow();//获得屏幕的HWND.
HDC hScreenDC = ::GetDC(hWnd);   //获得屏幕的HDC.
HDC MemDC = ::CreateCompatibleDC(hScreenDC);
RECT rect; 
::GetWindowRect(hWnd,&rect);
SIZE screensize;
screensize.cx=rect.right-rect.left;
screensize.cy=rect.bottom-rect.top;
hBitmap = ::CreateCompatibleBitmap(hScreenDC,screensize.cx,screensize.cy);
HGDIOBJ hOldBMP = ::SelectObject(MemDC,hBitmap);
::BitBlt(MemDC,0,0,screensize.cx,screensize.cy,hScreenDC,rect.left,rect.top,SRCCOPY);
::SelectObject(MemDC,hOldBMP);
::DeleteObject(MemDC);
::ReleaseDC(hWnd,hScreenDC);
CDC *pDC=GetDC();
HDC dDlgDC=pDC->m_hDC;
HDC MemDC1 = CreateCompatibleDC(dDlgDC);
HGDIOBJ hOldBMP1 = ::SelectObject(MemDC1,hBitmap);
::StretchBlt(dDlgDC,15,15,715,515,MemDC1,0,0,700,500,SRCCOPY);
::SelectObject(MemDC1,hOldBMP1);
::DeleteObject(MemDC1);
::ReleaseDC(m_hWnd,dDlgDC); //scrylm=screensize.cy-500;
//scrxlm=screensize.cx-700;
/*m_vbar.SetScrollRange(0,screensize.cy-500,TRUE);
m_vbar.SetScrollPos(0,TRUE);
m_hbar.SetScrollRange(0,screensize.cx-700,TRUE);
m_hbar.SetScrollPos(0,TRUE);*/
//capflag=1;
}void CCatchScreenDlg::WriteBmpToFile(HBITMAP hBitmap,CString strFileName)
{
HDC hDC =::CreateDC(_T("DISPLAY"),NULL,NULL,NULL); 
int iBits = ::GetDeviceCaps(hDC, BITSPIXEL) * ::GetDeviceCaps(hDC, PLANES);//当前分辨率下每个像素所占字节数  
::DeleteDC(hDC); WORD   wBitCount;   //位图中每个像素所占字节数    
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 = iBits; DWORD   dwPaletteSize=0; //调色板大小， 位图中像素字节大小 
if (wBitCount <= 8)
dwPaletteSize = (1 << wBitCount) * sizeof(RGBQUAD);
BITMAP  bm;        //位图属性结构
::GetObject(hBitmap, sizeof(bm), (LPSTR)&bm);  
BITMAPINFOHEADER   bi,bi1;       //位图信息头结构     
bi.biSize            = sizeof(BITMAPINFOHEADER);  
bi.biWidth           = bm.bmWidth;
bi.biHeight          = bm.bmHeight;
bi.biPlanes          = 1;
bi.biBitCount        = wBitCount;
bi.biCompression     = BI_RGB; //BI_RGB表示位图没有压缩
bi.biSizeImage       = 0;
bi.biXPelsPerMeter   = 0;
bi.biYPelsPerMeter   = 0;
bi.biClrUsed         = 0;
bi.biClrImportant    = 0;
bi1=bi;
bi1.biBitCount=24; DWORD dwBmBitsSize = ((bm.bmWidth * wBitCount+31)/32) * 4 * bm.bmHeight;    
HANDLE hDib  = ::GlobalAlloc(GHND,dwBmBitsSize + dwPaletteSize + sizeof(BITMAPINFOHEADER));  //为位图内容分配内存
LPBITMAPINFOHEADER lpbi = (LPBITMAPINFOHEADER)GlobalLock(hDib);
*lpbi = bi; HANDLE hPal = ::GetStockObject(DEFAULT_PALETTE);  // 处理调色板 
HANDLE  hOldPal=NULL; 
if (hPal)
{
hDC = ::GetDC(NULL);
hOldPal = SelectPalette(hDC,(HPALETTE)hPal, FALSE);
RealizePalette(hDC);
}
int nOutputBytes = 0;
unsigned char *pJpp,*m_pDibBits;
pJpp = new unsigned char [dwBmBitsSize];
m_pDibBits = new unsigned char [dwBmBitsSize];
//::GetDIBits(hDC, hBitmap, 0, (UINT) bm.bmHeight,m_pDibBits,(BITMAPINFO*)lpbi,DIB_RGB_COLORS);
::GetDIBits(hDC, hBitmap, 0, (UINT) bm.bmHeight,(LPSTR)lpbi + sizeof(BITMAPINFOHEADER)+dwPaletteSize,(BITMAPINFO*)lpbi,DIB_RGB_COLORS);// 获取该调色板下新的像素值
if (hOldPal)//恢复调色板
{
SelectPalette(hDC, (HPALETTE)hOldPal, TRUE);
RealizePalette(hDC);
::ReleaseDC(NULL, hDC);
}
/* memcpy(m_pDibBits,(LPSTR)lpbi+sizeof(BITMAPINFOHEADER)+dwPaletteSize,dwBmBitsSize);
int i=0,j=0; for(j=0;j<dwBmBitsSize;j++)
{
if(j%4==3)
j++;
m_pDibBits[i]=m_pDibBits[j];
i++;
}*/
BITMAPFILEHEADER   bmfHdr; //位图文件头结构     
bmfHdr.bfType = 0x4D42;  // "BM"   // 设置位图文件头
DWORD 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; HANDLE hFile = CreateFile(strFileName, GENERIC_WRITE, 0, NULL, CREATE_ALWAYS,FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN, NULL);//创建位图文件   
DWORD dwWritten;
WriteFile(hFile, (LPSTR)&bmfHdr, sizeof(BITMAPFILEHEADER), &dwWritten, NULL); // 写入位图文件头
WriteFile(hFile, (LPSTR)lpbi, dwDIBSize, &dwWritten, NULL);// 写入位图文件其余内容
GlobalUnlock(hDib);   //清除   
GlobalFree(hDib);
CloseHandle(hFile); 
delete []pJpp;
delete []m_pDibBits;
}