[OpenCV] Install openCV in Qt Creator

Learn openCV.pdf

---

qmake: link with opencv (Key Point)

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = displayimage
TEMPLATE = app

INCLUDEPATH += /usr/local/include/opencv
LIBS += -L/usr/local/lib -lopencv_core -lopencv_imgproc -lopencv_highgui

SOURCES += main.cpp\
        mainwindow.cpp

HEADERS  += mainwindow.h

FORMS    += mainwindow.ui

main.cpp

#include "mainwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <opencv2/opencv.hpp>　　//add

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
cv::Mat inputImage = cv::imread("/home/unsw/Pictures/me/lolo.JPG");　　//add
cv::imshow("Display Image", inputImage);　　//add
}

MainWindow::~MainWindow()
{
    delete ui;
}

---

ch2_ex2_1: 打开并显示图片

#include "highgui.h"

int main( int argc, char** argv )
{
    // IplImage* img = cvLoadImage( argv[1] );
    IplImage* img = cvLoadImage( "/home/unsw/Pictures/me/lolo.JPG",
                                 CV_WINDOW_AUTOSIZE);

    cvNamedWindow("lolo", CV_WINDOW_FREERATIO);
    cvShowImage("lolo", img );
    cvWaitKey();
    cvReleaseImage( &img );
    cvDestroyWindow("lolo");
}

---

ch2_ex2_2: 打开并显示视频

int main( int argc, char** argv ) {
    cvNamedWindow( "Example2", CV_WINDOW_AUTOSIZE );
    //CvCapture* capture = cvCaptureFromAVI( argv[1] ); // either one will work
    CvCapture* capture = cvCreateFileCapture( "/home/unsw/test.avi" ); // 放每一帧的buf
    IplImage* frame;
    while() {
        frame = cvQueryFrame( capture );
        if( !frame ) break;
        cvShowImage( "Example2", frame );　　//不需要手动释放，capture的释放即顺便将其释放
        char c = cvWaitKey();　　　　　　　　//33ms, 30frames per second.
        if( c ==  ) break;
    }
    cvReleaseCapture( &capture );
    cvDestroyWindow( "Example2" );
}

---

ch2_ex2_3: 打开并显示视频 + Control Bar

可以使用QT的图形界面控制，非重点here。

---

ch2_ex2_4: 平滑处理图片

#include "cv.h"
#include "highgui.h"

void example2_4( IplImage* image )
{
    // Create some windows to show the input
    // and output images in.
    //
    cvNamedWindow( "Example2_4-in", CV_WINDOW_AUTOSIZE );
    cvNamedWindow( "Example2_4-out", CV_WINDOW_AUTOSIZE );

    // Create a window to show our input image
    //
    cvShowImage( "Example2_4-in", image );

    // Create an image to hold the smoothed output
    //
    IplImage* out = cvCreateImage(
        cvGetSize(image),
        IPL_DEPTH_8U,

    );

    // Do the smoothing
    //
cvSmooth( image, out, CV_GAUSSIAN, ,5,0,0 );
cvSmooth( out, out, CV_GAUSSIAN, ,5,0,0);

    // Show the smoothed image in the output window
    //
    cvShowImage( "Example2_4-out", out );

    // Be tidy
    //
    cvReleaseImage( &out );

    // Wait for the user to hit a key, then clean up the windows
    //
    cvWaitKey(  );
    cvDestroyWindow("Example2_4-in" );
    cvDestroyWindow("Example2_4-out" );

}

int main( int argc, char** argv )
{
  IplImage* img = cvLoadImage( argv[] );
  cvNamedWindow("Example1", CV_WINDOW_AUTOSIZE );
  cvShowImage("Example1", img );
  example2_4( img );
//  cvWaitKey(0);
  cvReleaseImage( &img );
  cvDestroyWindow("Example1");
}

---

ch2_ex2_8: 灰度化(Gray) --> 缩小图片(Pyr) --> 线条化(Canny)

#include "cv.h"
#include "highgui.h"

IplImage* doCanny(
    IplImage* in,
    double    lowThresh,
    double    highThresh,
    double    aperture)
{
    IplImage* out = cvCreateImage(
        cvGetSize( in ),
        in->depth, //IPL_DEPTH_8U,
        );
cvCanny( in, out, lowThresh, highThresh, aperture );
    return( out );
};

IplImage* doPyrDown(
  IplImage* in,
  int       filter = IPL_GAUSSIAN_5x5)
{

    // Best to make sure input image is divisible by two.
    //
    assert( in->width% ==  && in->height% ==  );

    IplImage* out = cvCreateImage(
        cvSize( in->width/, in->height/ ),
        in->depth,
        in->nChannels
    );
cvPyrDown( in, out );
    return( out );
};

int main( int argc, char** argv )
{
  cvNamedWindow("Example Gray",  CV_WINDOW_AUTOSIZE );
  cvNamedWindow("Example Pyr",   CV_WINDOW_AUTOSIZE );
  cvNamedWindow("Example Canny", CV_WINDOW_AUTOSIZE );
  IplImage* img_rgb = cvLoadImage( "/home/unsw/lolo.jpg" );
  IplImage* out;

  out = cvCreateImage( cvSize( img_rgb->width,img_rgb->height ), img_rgb->depth, );
cvCvtColor(img_rgb, out ,CV_BGR2GRAY);
  cvShowImage("Example Gray", out );
  out = doPyrDown( out );
  out = doPyrDown( out );
  cvShowImage("Example Pyr", out );
  out = doCanny( out, , ,  );
  cvShowImage("Example Canny", out );

  cvWaitKey();
  cvReleaseImage( &out);
  cvDestroyWindow("Example Gray");
  cvDestroyWindow("Example Pyr");
  cvDestroyWindow("Example Canny");
}

---

ch2_ex2_9: Camera: Preview & Capture

#include "cv.h"
#include "highgui.h"

int main( int argc, char** argv ) {
    cvNamedWindow( "Example2_9", CV_WINDOW_AUTOSIZE );
    CvCapture* capture;
    if (argc==) {
capture = cvCreateCameraCapture(  );
    } else {
        capture = cvCreateFileCapture( argv[] );
    }
    assert( capture != NULL );

    IplImage* frame;
    while() {
        frame = cvQueryFrame( capture );
        if( !frame ) break;
        cvShowImage( "Example2_9", frame );
        char c = cvWaitKey(4);
        if( c ==  ) break;
    }
    cvReleaseCapture( &capture );
    cvDestroyWindow( "Example2_9" );
}

---

ch2_ex2_10: 写入视频文件

#include "cv.h"
#include "highgui.h"
#include <stdio.h>
#include <iostream>

using namespace std;

// Convert a video to grayscale
// argv[1]: input video file
// argv[2]: name of new output file
//

//#define NOWRITE 1;   //Turn this on (removed the first comment out "//" if you can't write on linux

main( int argc, char* argv[] ) {
    cvNamedWindow( "Example2_10", CV_WINDOW_AUTOSIZE );
    cvNamedWindow( "Log_Polar", CV_WINDOW_AUTOSIZE );
    CvCapture* capture = cvCreateFileCapture( "/home/unsw/test.avi" );
    if (!capture){
        return -;
    }
    IplImage* bgr_frame;
    double fps = cvGetCaptureProperty (
        capture,
        CV_CAP_PROP_FPS
    );
    printf("fps=%d\n",(int)fps);

    CvSize size = cvSize(
        (int)cvGetCaptureProperty( capture, CV_CAP_PROP_FRAME_WIDTH),
        (int)cvGetCaptureProperty( capture, CV_CAP_PROP_FRAME_HEIGHT)
    );

    printf("frame (w, h) = (%d, %d)\n",size.width,size.height);
#ifndef NOWRITE
 CvVideoWriter* writer = cvCreateVideoWriter(  // On linux Will only work if you've installed ffmpeg development files correctly,
        "/home/unsw/test_out.avi",                               // otherwise segmentation fault.  Windows probably better.
        CV_FOURCC('D','X','',''),
        fps,
        size
    );
#endif
    IplImage* logpolar_frame = cvCreateImage(
        size,
        IPL_DEPTH_8U,

    );

    IplImage* gray_frame = cvCreateImage(
        size,
        IPL_DEPTH_8U,

    );

    while( (bgr_frame=cvQueryFrame(capture)) != NULL ) {
        cvShowImage( "Example2_10", bgr_frame );
        cvConvertImage(   //We never make use of this gray image
            bgr_frame,
            gray_frame,
            CV_RGB2GRAY
        );
        cvLogPolar( bgr_frame, logpolar_frame,  //This is just a fun conversion the mimic's the human visual system
                    cvPoint2D32f(bgr_frame->width/,
                    bgr_frame->height/),
                    ,
                    CV_INTER_LINEAR+CV_WARP_FILL_OUTLIERS );
        cvShowImage( "Log_Polar", logpolar_frame );
        //Sigh, on linux, depending on your ffmpeg, this often won't work ...
#ifndef NOWRITE
       cvWriteToAVI( writer, logpolar_frame );
#endif
        char c = cvWaitKey();
        if( c ==  ) break;
    }
#ifndef NOWRITE
    cvReleaseVideoWriter( &writer );
#endif
    cvReleaseImage( &gray_frame );
    cvReleaseImage( &logpolar_frame );
    cvReleaseCapture( &capture );
}