[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：

public:
    GDALDataset* m_pDataset; 
    double m_dScale;            //现有图框与图像的比值

    int m_iMinx;
    int m_iMiny;
    int m_iMaxx;
    int m_iMaxy;
    void ShowRaster();

在实现文件中添加如下代码：

void DlgFastShow::OnBnClickedBtnOpenimage()
{
    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());
    CString str;
    if (dlg.DoModal()==IDOK)
    {
        str=dlg.GetPathName();
        GDALAllRegister();  
        CPLSetConfigOption("GDAL_FILENAME_IS_UTF8","NO");
        const char* pszFile =(LPCTSTR)str;
         
        //使用只读方式打开图像   
        m_pDataset = (GDALDataset*)GDALOpen(pszFile,GA_ReadOnly); 
        if( m_pDataset == NULL )  
        {  
            CString ex;
            ex.AppendFormat("File: %s不能打开！\n",str);        
        }  
        double padfTransform[6] = {0.0};
        m_pDataset->GetGeoTransform(padfTransform);
        ShowRaster();
    }
}
    void DlgFastShow::ShowRaster()
    {
        int iStartCol = 0;  
        int iStartRow = 0;      
        int dataWidth = m_pDataset->GetRasterXSize();//spinEndCol->value() - iStartCol;  
        int dataHeight =m_pDataset->GetRasterYSize();// spinEndRow->value() - iStartRow;  
        int dataBands =  m_pDataset->GetRasterCount(); 
        CString ex;
        ex.AppendFormat("行列数目: %d %d %d",dataWidth,dataHeight,dataBands);    
        int band_list[3] = {3,2,1};  

        m_dScale = dataHeight > dataWidth ? dataHeight : dataWidth;  
        int iViewHeight = 478;  
        m_dScale = iViewHeight/m_dScale;  

        int iSize = GDALGetDataTypeSize(GDT_Byte) / 8;//以字节为单位
        int iScaleWidth = static_cast<int>(dataWidth*m_dScale+0.5);  
        int iScaleHeight = static_cast<int>(dataHeight*m_dScale+0.5);  
        ex.AppendFormat("缓存数目: %d %d",iScaleWidth,iScaleHeight);    
        iScaleWidth = (iScaleWidth*8+31)/32*4;
        ex.AppendFormat("取整数目: %d ",iScaleWidth);    
        AfxMessageBox(ex);
        unsigned char* pBuffer = new unsigned char[iScaleWidth*iScaleHeight*3];  
        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   

        unsigned char* pDataBuffer = NULL;  
        if (dataBands >=3 )  
        {  
            pDataBuffer = pBuffer;  
        }  
        else  
        {  
            pDataBuffer = new unsigned char[iScaleWidth*iScaleHeight*3];  
            for (int i=0; i<iScaleWidth*iScaleHeight*3; i++)  
                pDataBuffer[i] = pBuffer[i/3];  
            delete []pBuffer;  
        }  

        /*CBitmap bitmap;            
        int flag=bitmap.CreateBitmap(iScaleWidth, iScaleHeight,1,24,pDataBuffer );*/
//int flag=bitmap.CreateCompatibleBitmap(iScaleWidth, iScaleHeight,1,32,pDataBuffer );
        /*if (flag==0)
        {
            AfxMessageBox("创建位图失败！");
        }*/
        //HBITMAP hBmp;    // 保存CBitmap加载的位图的句柄      
        //hBmp = (HBITMAP)bitmap.GetSafeHandle();  // 获取bitmap加载位图的句柄            
         
        //picImage.SetBitmap(hBmp);  
        //CClientDC dc(this);
        //BITMAP bm;
        //bitmap.GetObject(sizeof    (BITMAP),&bm);
        //CDC dcMem;
        //dcMem.CreateCompatibleDC(&dc);
        //CBitmap *pOldbmp=dcMem.SelectObject(&bitmap);
        //CDC *pDC=&dc;
        //pDC->BitBlt(0,0,bm.bmWidth,bm.bmHeight,&dcMem,0,0,SRCCOPY);
        //dcMem.SelectObject(pOldbmp);


        CDC dc;
        CClientDC cdc(this);

        dc.Attach(cdc.m_hDC);

        CDC memDC;
        memDC.CreateCompatibleDC(&dc);

        CBitmap bmp;
        bmp.CreateCompatibleBitmap(&dc,500,500);
        memDC.SelectObject(&bmp);

        BITMAPINFO bmpInfo;
        bmpInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
        bmpInfo.bmiHeader.biWidth = iScaleWidth;
        bmpInfo.bmiHeader.biHeight = -iScaleHeight;
        //bmpInfo.bmiHeader.biWidth = 487;
        //bmpInfo.bmiHeader.biHeight = -500;
        bmpInfo.bmiHeader.biPlanes = 1;
        bmpInfo.bmiHeader.biBitCount = 24;//24位色
        bmpInfo.bmiHeader.biCompression = BI_RGB;
        bmpInfo.bmiHeader.biSizeImage = 0;
        bmpInfo.bmiHeader.biXPelsPerMeter = 3000;
        bmpInfo.bmiHeader.biYPelsPerMeter = 3000;
        bmpInfo.bmiHeader.biClrUsed = 0;
        bmpInfo.bmiHeader.biClrImportant = 0;

        //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         }*/

        SetDIBits(dc.m_hDC,bmp,0,iScaleHeight,pDataBuffer,&bmpInfo,DIB_RGB_COLORS);
        //delete []pData;
        cdc.BitBlt(0,0,500,500,&memDC,0,0,SRCCOPY);
        delete []pDataBuffer; 
        
    }

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。