Question

我一直在尝试在MFC中显示jpg图像，但我无法得到它。我是一个完整的MFC新手，我到现在为止所做的一切大部分都是根据我在网上找到的东西改编的。目前我有这个：

Picture.h：

#pragma once
#include <afxwin.h>

class Picture
{
public:
   Picture();

   bool load(LPCTSTR filePath);

   bool draw( CDC* deviceContext
            , CRect clientRect
            , LPCRECT prcMFBounds);

   CSize getSize(CDC* pDC);

private:
   LPPICTURE m_picture;
};

Picture.cpp：

#include "Picture.h"

Picture::Picture()
   : m_picture(0)
{
}

bool Picture::load(LPCTSTR szFile)
{
   HANDLE hFile = CreateFile(szFile, GENERIC_READ, 0, NULL, OPEN_EXISTING, 0, NULL);
   if (hFile == INVALID_HANDLE_VALUE)
      return false;

   DWORD dwFileSize = GetFileSize(hFile, NULL);
   if (dwFileSize == (DWORD)-1)
   {
      CloseHandle(hFile);
      return false;
   }

   LPVOID pvData = NULL;

   // alloc memory based on file size
   HGLOBAL hGlobal = GlobalAlloc(GMEM_MOVEABLE, dwFileSize);
   if (hGlobal == NULL)
   {
      CloseHandle(hFile);
      return false;
   }

   pvData = GlobalLock(hGlobal);

   if (pvData == NULL)
   {
      GlobalUnlock(hGlobal);
      CloseHandle(hFile);
      return false;
   }

   DWORD dwBytesRead = 0;

   // read file and store in global memory
   bool bRead = ReadFile(hFile, pvData, dwFileSize, &dwBytesRead, NULL) != 0;

   GlobalUnlock(hGlobal);
   CloseHandle(hFile);

   if (!bRead)
      return false;

   LPSTREAM pstm = NULL;

   // create IStream* from global memory
   HRESULT hr = CreateStreamOnHGlobal(hGlobal, TRUE, &pstm);
   if (!(SUCCEEDED(hr)))
   {
      if (pstm != NULL)
         pstm->Release();
      return false;
   }

   else if (pstm == NULL)
      return false;

   // Create IPicture from image file
   if (m_picture)
      m_picture->Release();

   hr = ::OleLoadPicture(pstm, dwFileSize, FALSE, IID_IPicture, (LPVOID *)&(m_picture));
   if (!(SUCCEEDED(hr)))
   {
      pstm->Release();
      return false;
   }

   else if (m_picture == NULL)
   {
      pstm->Release();
      return false;
   }
   pstm->Release();

   return true;
}

bool Picture::draw(CDC* deviceContext, CRect clientRect, LPCRECT prcMFBounds)
{
   if (clientRect.IsRectNull())
   {
      CSize imageSize = getSize(deviceContext);
      clientRect.right = imageSize.cx;
      clientRect.bottom = imageSize.cy;
   }

   long pictureWidth = 0;
   long pictureHeigth = 0;

   m_picture->get_Width(&pictureWidth);
   m_picture->get_Height(&pictureHeigth);

   m_picture->Render( *deviceContext
                    , clientRect.left
                    , clientRect.top
                    , clientRect.Width()
                    , clientRect.Height()
                    , 0
                    , pictureHeigth
                    , pictureWidth
                    , -pictureHeigth
                    , prcMFBounds);
   return true;
}

CSize Picture::getSize(CDC* deviceContext)
{
   if (!m_picture)
      return CSize(0,0);

   LONG width, height; // HIMETRIC units
   m_picture->get_Width(&width);
   m_picture->get_Height(&height);
   CSize size(width, height);
   if (deviceContext==NULL)
   {
      CWindowDC dc(NULL);
      dc.HIMETRICtoDP(&size); // convert to pixels
   }
   else
   {
      deviceContext->HIMETRICtoDP(&size);
   }
   return size;
}

PictureView.h：

#pragma once

#include <afxwin.h>
#include <string>

class Picture;

class PictureView : public CStatic
{
public:
   PictureView(std::string path);

protected:
   virtual void DrawItem(LPDRAWITEMSTRUCT lpDrawItemStruct);

private:
   Picture* m_picture;
};

PictureView.cpp：

#include "PictureView.h"
#include "Picture.h"

PictureView::PictureView(std::string path)
{
   m_picture = new Picture();
   m_picture->load(path.c_str());
}

void PictureView::DrawItem(LPDRAWITEMSTRUCT /*lpDrawItemStruct*/)
{
   CRect rect;
   GetClientRect(&rect);
   m_picture->draw(GetDC(), rect, rect);
}

构造函数调用：

CWnd* GenericChildWidget::addImage(std::string path, int horizontalPos, int width, int verticalPos, int height, int childId)
{
   PictureView* image = new PictureView(path);
   image->Create("", SS_OWNERDRAW, CRect(horizontalPos, verticalPos, width + horizontalPos, height + verticalPos), this, childId);
   return image;
}

问题是我无法调用DrawItem函数。我究竟做错了什么？任何帮助将不胜感激。

Answer 1

这是在MFC对话框中绘制图像的简便方法：

与gdiplus.dll

链接

#include "atlimage.h>
#include "gdiplus.h>
using namespace Gdiplus
.
.
.

CImage ci;

ci.Load((CString)"D:\\Pictures\\mycat.jpg");

CDC *dc = AfxGetMainWnd()->GetDC();

HDC hdc = *dc;

ci.Draw(hdc,10,10);

希望它有效！

Answer 2

我不确定调用m_picture-＆gt; draw中的GetDC是否必须引用CREATESTRUCT中给出的相同DC。我所做的是：

      CDC* pDC = CDC::FromHandle(lpDrawItemStruct->hDC);

编辑：由于我无法发表评论，希望编辑就足够了。我认为你的同事错了，因为我最近刚使用SS_OWNERDRAW实现了一个CStatic控件。我猜想增加了WS_CHILD | Create调用上的WS_VISIBLE是关键。

Answer 3

在我的一位同事的帮助下，我找到了答案。他告诉我，不可能拥有一个所有权的CStatic。因此，当我现在从CButton继承PictureView并使其成为BS_OWNERDRAW时，我的图像将被渲染。

就我个人而言，我认为这是一个丑陋的解决方案，但我现在已经厌倦了这个问题，因为我并不那么在意。这些是我为使其发挥作用所做的改变：

构造函数调用：

CWnd* GenericChildWidget::addImage(std::string path, int horizontalPos, int width, int verticalPos, int height, int childId)
{
   PictureView* image = new PictureView(path);
   image->Create("", BS_OWNERDRAW | WS_CHILD | WS_VISIBLE, CRect(horizontalPos, verticalPos, width + horizontalPos, height + verticalPos), this, childId);
   return image;
}

PictureView.h：

#pragma once

#include <afxwin.h>
#include <string>

class Picture;

class PictureView : public CButton
{
public:
   PictureView(std::string path);

protected:
   virtual void DrawItem(LPDRAWITEMSTRUCT lpDrawItemStruct);

private:
   Picture* m_picture;
};

感谢所有人的帮助。

Answer 4

我从未使用过MFC，但快速阅读CStatic::DrawItem documentation表示必须使用SS_OWNERDRAW样式创建DrawItem才能调用它。您没有为Create显示PictureView行，所以也许就是这样？

在MFC中绘制jpg

4 个答案: