基于dcmtk的dicom工具 第十一章 加载dicom文件多帧图数据

---

前言

继前一章，本章实现多帧图显示，增加“上一帧”、“下一帧”两个按钮，和鼠标滚动消息滚动不同帧。
效果如下：

---

一、加载多帧图的方法

1. DicomImage 构造函数

下面是dcmtk DicomImage类的一个构造函数，创建dcmtk DicomImage对象时，单帧图只需要填写前两个参数即可，多帧图flags参数填 CIF_UsePartialAccessToPixelData，再配合 fstart, fcount参数即可加载第fstart帧到 fstart+fcount帧的图像数据

 /** constructor, use a given DcmObject*** @param  object  pointer to DICOM data structures (fileformat, dataset or item).*                  (do not delete while referenced, i.e. while this image object or any*                   descendant exists; not deleted within dcmimage unless configuration flag*                   CIF_TakeOverExternalDataset is set - in this case do not delete it at all)*  @param  xfer    transfer syntax of the 'object'.*                  (could also be EXS_Unknown in case of fileformat or dataset)*  @param  flags   configuration flags (CIF_xxx, see diutils.h)*  @param  fstart  first frame to be processed (optional, 0 = 1st frame), all subsequent use*                  of parameters labeled 'frame' in this class refers to this start frame.*  @param  fcount  number of frames (optional, 0 = all frames)*/DicomImage(DcmObject *object,const E_TransferSyntax xfer,const unsigned long flags = 0,const unsigned long fstart = 0,const unsigned long fcount = 0);

2. DcmParser Open函数

DcmParser类中的Open, CreateDIB两个函数中处理多帧图的代码
Open函数中的代码，默认多帧图fcount=5，即只加载最多5帧数据到内存，可根据电脑内存修改：

BOOL DcmParser::Open(std::string dcmfile)
{if (m_bParserValid)return TRUE;dcmAcceptUnexpectedImplicitEncoding.set(OFFalse);dcmPreferVRFromDataDictionary.set(OFFalse);OFCondition cond;cond = m_dcmFile.loadFile(dcmfile.c_str());...if (m_nFrameCount == 1) {m_pDcmImg = new DicomImage(pDataset, m_newXfer);}else {   // 多帧图，只加载最多5帧数据m_nLoadCount = m_nFrameCount > 5 ? 5 : m_nFrameCount;m_nFrameStart = 0;unsigned long flag = CIF_UsePartialAccessToPixelData;m_pDcmImg = new DicomImage(pDataset, m_orgXfer, flag, m_nFrameStart, m_nLoadCount);}...return m_bParserValid;
}

3. DcmParser CreateDIB函数

对于多帧图，Open函数中默认加载的是前五帧的图像数据，索引[0,4]，当CreateDIB函数的frame参数值超过4时，需要加载下一个五帧的图像数据，索引[5,9]
最重要的四行代码：

1. int fend = m_nFrameStart + m_nLoadCount - 1; 用来判断frame是否超出范围
2. m_nFrameStart = frame / m_nLoadCount * m_nLoadCount; 计算新的起始帧索引
3. m_pDcmImg = new DicomImage(pDataset, m_orgXfer, flag, m_nFrameStart, m_nLoadCount); 加载新五帧数据
4. size = di->createWindowsDIB(pdib, 0, frame-m_nFrameStart, 24, 1); 创建当前frame帧位图数据

BOOL DcmParser::CreateDIB(void*& pdib, int& w, int& h, double wc, double ww, int frame/* = 0*/, bool bneg/* = false*/)
{DcmDataset* pDataset = m_dcmFile.getDataset();int fend = m_nFrameStart + m_nLoadCount - 1;if (!(frame >= m_nFrameStart && frame <= fend)) {m_nFrameStart = frame / m_nLoadCount * m_nLoadCount;delete m_pDcmImg;unsigned long flag = CIF_UsePartialAccessToPixelData;m_pDcmImg = new DicomImage(pDataset, m_orgXfer, flag, m_nFrameStart, m_nLoadCount);}...size = di->createWindowsDIB(pdib, 0, frame-m_nFrameStart, 24, 1);...}

4. 为Displayer类添加PrevFrame，NextFrame两个函数

在绘制参数DrawParam.nFrame中记录当前帧索引，只需要增减nFrame，再调用DcmParser中的CreateDIB重建生成位图数据即可。

void Displayer::PrevFrame()
{int nFrame = m_drawParam.nFrame - 1;if (nFrame < 0) {return;}m_drawParam.nFrame = nFrame;if (m_pDib){delete[] m_pDib;m_pDib = nullptr;}m_pImage->CreateDIB(m_pDib, m_drawParam.width, m_drawParam.height, m_drawParam.winCenter,m_drawParam.winWidth, m_drawParam.nFrame, m_drawParam.bNagtive);FitToView();
}void Displayer::NextFrame()
{int nFrameCount = m_pImage->GetFrameCount();int nFrame = m_drawParam.nFrame + 1;if (nFrame > nFrameCount - 1) {return;}m_drawParam.nFrame = nFrame;if (m_pDib){delete[] m_pDib;m_pDib = nullptr;}m_pImage->CreateDIB(m_pDib, m_drawParam.width, m_drawParam.height, m_drawParam.winCenter,m_drawParam.winWidth, m_drawParam.nFrame, m_drawParam.bNagtive);FitToView();
}

二、按钮滚动帧

1. 在对话框中添加“上一帧”，“下一帧”两个按钮
2. 在CDcmImageDlg中为按钮添加响应事件
3. 图像加载时检查dicom文件是否为多帧图，控制两个按钮是否变灰

void CDcmImageDlg::OnBnClickedButtonPrevFrame()
{m_disp.PrevFrame();
}void CDcmImageDlg::OnBnClickedButtonNextFrame()
{m_disp.NextFrame();
}void CDcmImageDlg::OnSelchangeListDcm()
{// TODO: 在此添加控件通知处理程序代码CString str;int idx = m_list.GetCurSel();m_list.GetText(idx, str);m_disp.LoadFile(str);int nFrames = m_disp.GetFrameCount();if (nFrames > 1) {GetDlgItem(IDC_BUTTON_PREV_FRAME)->EnableWindow(TRUE);GetDlgItem(IDC_BUTTON_NEXT_FRAME)->EnableWindow(TRUE);}else {GetDlgItem(IDC_BUTTON_PREV_FRAME)->EnableWindow(FALSE);GetDlgItem(IDC_BUTTON_NEXT_FRAME)->EnableWindow(FALSE);}}

三、鼠标滚轮滚动帧

Displayer类中添加鼠标滚轮消息WM_MOUSEWHEEL，调用NextFrame，PrevFrame滚动帧

BEGIN_MESSAGE_MAP(Displayer, CWnd)ON_WM_PAINT()ON_WM_SIZE()ON_WM_MOUSEWHEEL()   // 鼠标滚轮
END_MESSAGE_MAP()BOOL Displayer::OnMouseWheel(UINT nFlags, short zDelta, CPoint pt)
{// TODO: 在此添加消息处理程序代码和/或调用默认值if (!m_pImage) return true;int nFrames = m_pImage->GetFrameCount();if (nFrames > 1) {if (zDelta < 0) {NextFrame();}else {PrevFrame();}}return CWnd::OnMouseWheel(nFlags, zDelta, pt);
}