[GDAL]4.影像的读取和显示

RasterIO的用法参考：

在MFC项目中添加一个对话框DlgFastShow，添加一个按钮 ，在头文件中添加如下代码：

1 public:

2     GDALDataset* m_pDataset; 

3     double m_dScale;            //现有图框与图像的比值

4 

5     int m_iMinx;

6     int m_iMiny;

7     int m_iMaxx;

8     int m_iMaxy;

9     void ShowRaster();

在实现文件中添加如下代码：

  1 void DlgFastShow::OnBnClickedBtnOpenimage()

  2 {

  3     CFileDialog dlg(TRUE,NULL,NULL,OFN_HIDEREADONLY|OFN_OVERWRITEPROMPT,_T("IMG影像文件(*.img)|*.img|TIFF影像文件(*.tif)|*.tif||"),AfxGetMainWnd());

  4     CString str;

  5     if (dlg.DoModal()==IDOK)

  6     {

  7         str=dlg.GetPathName();

  8         GDALAllRegister();  

  9         CPLSetConfigOption("GDAL_FILENAME_IS_UTF8","NO");

 10         const char* pszFile =(LPCTSTR)str;

 11          

 12         //使用只读方式打开图像   

 13         m_pDataset = (GDALDataset*)GDALOpen(pszFile,GA_ReadOnly); 

 14         if( m_pDataset == NULL )  

 15         {  

 16             CString ex;

 17             ex.AppendFormat("File: %s不能打开！\n",str);        

 18         }  

 19         double padfTransform[6] = {0.0};

 20         m_pDataset->GetGeoTransform(padfTransform);

 21         ShowRaster();

 22     }

 23 }

 24     void DlgFastShow::ShowRaster()

 25     {

 26         int iStartCol = 0;  

 27         int iStartRow = 0;      

 28         int dataWidth = m_pDataset->GetRasterXSize();//spinEndCol->value() - iStartCol;  

 29         int dataHeight =m_pDataset->GetRasterYSize();// spinEndRow->value() - iStartRow;  

 30         int dataBands =  m_pDataset->GetRasterCount(); 

 31         CString ex;

 32         ex.AppendFormat("行列数目: %d %d %d",dataWidth,dataHeight,dataBands);    

 33         int band_list[3] = {3,2,1};  

 34 

 35         m_dScale = dataHeight > dataWidth ? dataHeight : dataWidth;  

 36         int iViewHeight = 478;  

 37         m_dScale = iViewHeight/m_dScale;  

 38 

 39         int iSize = GDALGetDataTypeSize(GDT_Byte) / 8;//以字节为单位

 40         int iScaleWidth = static_cast<int>(dataWidth*m_dScale+0.5);  

 41         int iScaleHeight = static_cast<int>(dataHeight*m_dScale+0.5);  

 42         ex.AppendFormat("缓存数目: %d %d",iScaleWidth,iScaleHeight);    

 43         iScaleWidth = (iScaleWidth*8+31)/32*4;

 44         ex.AppendFormat("取整数目: %d ",iScaleWidth);    

 45         AfxMessageBox(ex);

 46         unsigned char* pBuffer = new unsigned char[iScaleWidth*iScaleHeight*3];  

 47         CPLErr err = m_pDataset->RasterIO(GF_Read, 0, 0,dataWidth, dataHeight, pBuffer, iScaleWidth, iScaleHeight,GDT_Byte, 3, band_list, iSize*3, iSize*iScaleWidth*3, iSize);   //读取3个波段的数据   

 48 

 49         unsigned char* pDataBuffer = NULL;  

 50         if (dataBands >=3 )  

 51         {  

 52             pDataBuffer = pBuffer;  

 53         }  

 54         else  

 55         {  

 56             pDataBuffer = new unsigned char[iScaleWidth*iScaleHeight*3];  

 57             for (int i=0; i<iScaleWidth*iScaleHeight*3; i++)  

 58                 pDataBuffer[i] = pBuffer[i/3];  

 59             delete []pBuffer;  

 60         }  

 61 

 62         /*CBitmap bitmap;            

 63         int flag=bitmap.CreateBitmap(iScaleWidth, iScaleHeight,1,24,pDataBuffer );*/

 64 //int flag=bitmap.CreateCompatibleBitmap(iScaleWidth, iScaleHeight,1,32,pDataBuffer );

 65         /*if (flag==0)

 66         {

 67             AfxMessageBox("创建位图失败！");

 68         }*/

 69         //HBITMAP hBmp;    // 保存CBitmap加载的位图的句柄      

 70         //hBmp = (HBITMAP)bitmap.GetSafeHandle();  // 获取bitmap加载位图的句柄            

 71          

 72         //picImage.SetBitmap(hBmp);  

 73         //CClientDC dc(this);

 74         //BITMAP bm;

 75         //bitmap.GetObject(sizeof    (BITMAP),&bm);

 76         //CDC dcMem;

 77         //dcMem.CreateCompatibleDC(&dc);

 78         //CBitmap *pOldbmp=dcMem.SelectObject(&bitmap);

 79         //CDC *pDC=&dc;

 80         //pDC->BitBlt(0,0,bm.bmWidth,bm.bmHeight,&dcMem,0,0,SRCCOPY);

 81         //dcMem.SelectObject(pOldbmp);

 82 

 83 

 84         CDC dc;

 85         CClientDC cdc(this);

 86 

 87         dc.Attach(cdc.m_hDC);

 88 

 89         CDC memDC;

 90         memDC.CreateCompatibleDC(&dc);

 91 

 92         CBitmap bmp;

 93         bmp.CreateCompatibleBitmap(&dc,500,500);

 94         memDC.SelectObject(&bmp);

 95 

 96         BITMAPINFO bmpInfo;

 97         bmpInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);

 98         bmpInfo.bmiHeader.biWidth = iScaleWidth;

 99         bmpInfo.bmiHeader.biHeight = -iScaleHeight;

100         //bmpInfo.bmiHeader.biWidth = 487;

101         //bmpInfo.bmiHeader.biHeight = -500;

102         bmpInfo.bmiHeader.biPlanes = 1;

103         bmpInfo.bmiHeader.biBitCount = 24;//24位色

104         bmpInfo.bmiHeader.biCompression = BI_RGB;

105         bmpInfo.bmiHeader.biSizeImage = 0;

106         bmpInfo.bmiHeader.biXPelsPerMeter = 3000;

107         bmpInfo.bmiHeader.biYPelsPerMeter = 3000;

108         bmpInfo.bmiHeader.biClrUsed = 0;

109         bmpInfo.bmiHeader.biClrImportant = 0;

110 

111         //每行字节数，4字节对齐

112         /*long nLnBytes = (487+3)/4*4*3;

113 

114         BYTE *pData = new BYTE[nLnBytes*500];

115         memset(pData,0,nLnBytes*500);

116         for(int i=10; i<90; i++)

117         {

118             pData[50*nLnBytes+i*3]=255;

119             pData[i*nLnBytes+50*3+2]=255;

120         }*/

121 

122         SetDIBits(dc.m_hDC,bmp,0,iScaleHeight,pDataBuffer,&bmpInfo,DIB_RGB_COLORS);

123  //delete []pData; 124         cdc.BitBlt(0,0,500,500,&memDC,0,0,SRCCOPY);

125         delete []pDataBuffer; 

126         

127     }

存在问题：屏幕一刷新，绘制的图像就没有了。

主要DDB（设备相关位图）和DIB（设备无关位图）的区别。采用了CreateCompatibleBitmap将byte数组创建为位图，采用CreateBitmap始终创只能建黑白图像。