QT中使用GDAL多线程读取遥感图像到QImage

GDAL 是一个很强大的可以读取很多格式 的带有GIS信息的栅格型图像。前阵子项目中需要读取遥感图像，并显示到QT界面，由于遥感图像一般很大，所以采取新开一个读图线程的方式来读取，防止界面假死。下面是代码共享，测试通过读取500MB的24000*24000像素GeoTiff图并在QT的QGraphicsView中显示。

 

环境：VS2005+SP1, Qt 4.6.0, GDAL 1.6.2

文件：commontoolfunctions.h, gdalimagereaderthread.h, gdalimagereaderthread.cpp

 

commontoolfunctions.h文件如下：

/* * 工具函数：网上找来的根据两点的经纬度坐标计算两个点的大地距离。 */ #ifndef COMMONTOOLFUNCTIONS_H #define COMMONTOOLFUNCTIONS_H #include <math.h> #define EARTH_RADIUS 6378.137 #define MY_PI 3.14159265358979 #define LB_CONVERT_TO_RAD(d) (d * MY_PI / 180.0) /* * 输入经纬度坐标，单位'度'。 * 返回值单位为公里。 * code from google maps. 近似值. */ double CalcDistanceByLB(double lat1, double lng1, double lat2, double lng2) { double radLat1 = LB_CONVERT_TO_RAD(lat1); double radLat2 = LB_CONVERT_TO_RAD(lat2); double a = radLat1 - radLat2; double b = LB_CONVERT_TO_RAD(lng1) - LB_CONVERT_TO_RAD(lng2); double s = 2 * asin(sqrt(pow(sin(a/2),2) + cos(radLat1)*cos(radLat2)*pow(sin(b/2),2))); s = s * EARTH_RADIUS; return s; } #endif

 

gdalimagereaderthread.h文件如下：

/* * QT线程类：使用GDAL读取图像文件并转为QImage的线程。 * 创建：MulinB * 日期：2010-1-8 * 上次修改: 2010-06-20 * HUST-IPRAI-CVL */ #ifndef GDALIMAGEREADERTHREAD_H #define GDALIMAGEREADERTHREAD_H #include <QThread> #include <gdal_priv.h> //for GDAL class QImage; class RSI_MapCanvas; class RSI_ImageReaderThread : public QThread { Q_OBJECT public: RSI_ImageReaderThread(RSI_MapCanvas* pCanvas); ~RSI_ImageReaderThread(); public: void ReadFile(const QString& imageFileName); //使用该函数读取文件 protected: void run(); //线程函数 private: RSI_MapCanvas* m_pCanvas; QString m_imageFileName; private: //GDAL读取图像文件时的临时变量 GDALRasterBand* m_pBand_GDAL_; int m_nXSize_GDAL_; int m_nYSize_GDAL_; void* m_pDataBufStart_GDAL_; int m_nBufXSize_GDAL_; int m_nBufYSize_GDAL_; GDALDataType m_eBufDataType_GDAL_; int m_nBufPixSpace_GDAL_; int m_nBufLineSpace_GDAL_; private: enum IMG_OPEN_DRIVER_T { RSI_IMG_DRIVER_UNDEF = 0, //未定义的打开方式 RSI_USE_OPENCV, //使用opencv RSI_USE_GDAL, //使用GDAL }; private: //将图像宽度字节数32位对齐 inline int Get32bitAlignedWidthBytes(int nImgPixWidth, int nBytesPerPix); //GDAL buffer 转 QImage QImage* CvtGDALBufferToGrayQImage(uchar* &pafScanblock, int nImgSizeX, int nImgSizeY, GDALDataType pixType); //将非8位的灰度图转换为8位灰度图 template <class T> void CvtImgDataTo8bitGrayImg(T* pOrigData, int nImgSizeX, int nImgSizeXAligned32bit, int nImgSizeY, uchar* pNew8bitImgBuf, int nNewImgSizeXAligned32bit, T maxVal, T minVal); }; #endif // GDALIMAGEREADERTHREAD_H

 

 

gdalimagereaderthread.cpp文件如下：

/* * QT线程类：使用GDAL读取图像文件并转为QImage的线程。 * 创建：MulinB * 日期：2010-1-8 * 上次修改: 2010-06-20 * TODO: 1.图像分辨率转换计算貌似有问题... 2.代码比较乱，没时间整理...囧... * HUST-IPRAI-CVL */ #include "GDALImageReaderThread.h" #include "iplimagetoqimage.h" //for IplImage converting to QImage #include "commontoolfunctions.h" //for calculate distance by LB #include <cv.h> //for OpenCV #include <highgui.h> //for OpenCV #include <limits.h> //for INT_MAX, INT_MIN, ... #include <float.h> //for FLT_MAX, FLT_MIN, ... QMutex G_imageReadMutex; QWaitCondition G_imageReadComplete; RSI_ImageReaderThread::RSI_ImageReaderThread(RSI_MapCanvas* pCanvas) : m_pCanvas(pCanvas) { } RSI_ImageReaderThread::~RSI_ImageReaderThread() { } //线程函数 void RSI_ImageReaderThread::run() { //这里只将GDAL最费时的RasterIO()函数作为新线程 /* GDALRasterBand::RasterIO() parameters: eRWFlag Either GF_Read to read a region of data, or GT_Write to write a region of data. nXOff The pixel offset to the top left corner of the region of the band to be accessed. This would be zero to start from the left side. nYOff The line offset to the top left corner of the region of the band to be accessed. This would be zero to start from the top. nXSize The width of the region of the band to be accessed in pixels. nYSize The height of the region of the band to be accessed in lines. pData The buffer into which the data should be read, or from which it should be written. This buffer must contain at least nBufXSize * nBufYSize words of type eBufType. It is organized in left to right, top to bottom pixel order. Spacing is controlled by the nPixelSpace, and nLineSpace parameters. nBufXSize the width of the buffer image into which the desired region is to be read, or from which it is to be written. nBufYSize the height of the buffer image into which the desired region is to b