In qenhancedgraphicsview.h (and of course also in qenhancedgraphicsview.cpp) you should have functions wheelEvent, mouseMoveEvent and mousePressEvent. The mouseMoveEvent function is missing.

I tried to put an image on the keypoint_plugin, but adding an image will prompt me:

Plugin Error Message : "Select a secondary image first!"

cpp:void Keypoint_Plugin::processImage(const cv::Mat &inputImage, cv::Mat &outputImage)
{
if(secondImage.empty())
{
emit errorMessage("Select a secondary image first!");
return;
}
I'm not quite sure what secondImage is

I tried to compile samples but none of them work on my MacOS, e.g. regarding ch2 Hello_Qt_OpenCV I get like 20 Qt related errors. First error I think is related to Q_OBJECT macro (unknown type name 'QT_WARNING_PUSH') and then cascade of other Qt errors. It might be something related to mainwindow.ui or QMainWindow but I have no clue.

I tested my Qt 5.11 and Qt 5.12rc2 environment and both work with official samples. My OpenCV 3.4.3 setup also works (tested both C++ using Xcode and python bindings).
I'm using
MacOS 10.13.6 High Sierra
Xcode 10.1
Qt 5.11 and Qt 5.12rc2

hello,

void CopyMakeBorder_Plugin::setupUi(QWidget *parent)
{
    ui = new Ui::PluginGui;
    ui->setupUi(parent);
    QStringList items;
    items.append("BORDER_CONSTANT");
    items.append("BORDER_REPLICATE");
    items.append("BORDER_REFLECT");
    items.append("BORDER_WRAP");
    items.append("BORDER_REFLECT_101");
    ui->borderTypeComboBox->addItems(items);
    connect(ui->borderTypeComboBox,
            SIGNAL(currentIndexChanged(int)),
            this,
            SLOT(on_borderTypeComboBox_currentIndexChanged(int)));
}

I am a freshman on qt programming. Could you tell me how to address this problem?

when i build color _plugin.pro project in ch6, I got this error: cvplugininterface.h" No such file or directory.

furthermore, how can I load the whole ch.6 as explained in the reference, because it has been separated into many projects.

thanks in advance

Hello, I am reading chapter 7 of your new book on opencv3-qt5. For experimenting with the presented keypoint detection algorithms, I put the keypoint_plug in the context computer_vision project developed the previous chapters.

I have got a plugin error message: "Select a secondary image first!" (for the generated Computer Vision GUI, I loaded the image as shown in the book). Switching any algorithm available gives the message. I feel only image should be fine with keypoint detection rather than matching.

If I perform the matching operation, the interface is easily to be crashed for some reason.

Working environment: OpenCV3.4 + Qt5.8

Thanks

i tried to build and run the code it build and run but the actual output was not display i din get where the problem is i have tried all the possible way but can't find the solution even i try the any example it is same it build and run but it won't show the output.
SOURCE CODE
MAININDOW.CPP
//*
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
loadSettings();
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_pushButton_pressed()
{
QString fileName =QFileDialog::getOpenFileName(this,
"Open Input Image"
,QDir::currentPath(),
"Image(.Jpg .png .bmp)");
if (QFile::exists (fileName))
{
ui->lineEdit->setText(fileName);
}
}
void MainWindow::on_pushButton_2_pressed()
{
QString fileName =QFileDialog::getSaveFileName(this,"Select Output Image",
QDir::currentPath(),
".jpg;;.png;;.bmp");
if (!fileName.isEmpty())
{
ui->lineEdit_2->setText(fileName);
using namespace cv;
Mat inpImg, outImg;
inpImg = imread (ui->lineEdit-> text().toStdString());
if (ui->radioButton->isChecked())
cv::medianBlur(inpImg,outImg,5);
else if (ui->radioButton_2->isChecked())
cv::GaussianBlur(inpImg,outImg,Size(5,5),1.25);
imwrite(fileName.toStdString(),outImg);
if (ui->checkBox ->isChecked())
imshow("Output Image",outImg);
}
}
void MainWindow::closeEvent(QCloseEvent event)
{ int result = QMessageBox::warning(this,"Exit",
"Are you sure you want to close this program?",
QMessageBox::Yes,
QMessageBox::No);
if(result == QMessageBox::Yes)
{
saveSettings();
event->accept();
}
else
{
event->ignore();
}
}
void MainWindow::loadSettings()
{
QSettings settings("Packt", "window",this);
ui->lineEdit->setText(settings.value("lineEdit","").toString());
ui->lineEdit_2->setText(settings.value("lineEdit_2","").toString());
ui->radioButton->setChecked(settings.value("radioButton",true).toBool());
ui->radioButton_2->setChecked(settings.value("radioButton_2",false).toBool());
ui->checkBox->setChecked(settings.value("checkBox",false).toBool());
}
void MainWindow::saveSettings()
{
QSettings settings("Packt","window",this);
settings.setValue("lineEdit",
ui->lineEdit->text());
settings.setValue("lineEdit_2",
ui->lineEdit_2->text());
settings.setValue("radioButton",
ui->radioButton->isChecked());
settings.setValue("radioButton_2",
ui->radioButton_2->isChecked());
settings.setValue("checkBox",
ui->checkBox->isChecked());
}
//
MAINWINDOW.H
//

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include
#include
#include
#include
#include
#include
#include
#include "opencv2/opencv.hpp"
#include "opencv2/imgcodecs.hpp"
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private slots:
void on_pushButton_pressed();
protected:
void closeEvent(QCloseEvent event);
void on_pushButton_2_pressed();
private:
Ui::MainWindow ui;
void loadSettings();
void saveSettings();
};
#endif // MAINWINDOW_H
//
MAIN.CPP
//

#include "mainwindow.h"
#include
int main(int argc, char argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}
//

In file qcustomgraphicseffect.cpp byteCount is deprecated in Qt 5.10. You should use sizeInBytes instead. Of course, your book was published about a month before Qt 5.10, but people probably have installed a newer version of Qt than what is used in the book.

Instead of compute_vision.pro, you should use computer_vision.pro. Unless there is some hidden meaning or reason I haven't figured out.

I am following the instructions in the book page 226-233 to run the first example on copymakeboder_plugin. After building Computer_Vision project, there is no cvplugins folder generated in the build folder. My build results in three subfolders: copymakeborder_plugin, mainapp and temp_plugin.

I tried to copy the CopyMakeBorder_Plugin.lib (I assumed it was the library file needed) in the copymakeborder_plugin build folder, to the mainapp build folder, and then run the mainapp , but got the error message windows:

No Plugins This application cannot work without plugins! Make sure that/cvplugins/folder exists in the same folder as the application and that there are some filter plugins inside it.

Is this folder automatically generated after building?

I am using Qt5.8 with OpenCV3.4 in windows10.

Thanks in advance!

Hello
I am running this code in my Qt successfully but stucked in this problem :
QCameraImageCapture error: "Device does not support images capture."
what is this problem and how can solve it?

I am running the example project Hello_Qt_OpenCV in ch02 in QtCreater4.5 with opencv3.2. The only change I made to the original Hello_Qt_OpenCV .pro file is the link to my opencv library. The configuration of opencv in Qt works fine with other qt projects.

Three issues are shown in building the project:
File not found: mainwindow.obj: LNK2019: unresolved external symbol "void __cdecl cv::medianBlur(class cv::_InputArray const &,class cv::_OutputArray const &,int)" (?medianBlur@cv@@YAXAEBV_InputArray@1@AEBV_OutputArray@1@H@Z) referenced in function "private: void __cdecl MainWindow::on_outputPushButton_pressed(void)" (?on_outputPushButton_pressed@MainWindow@@AEAAXXZ)

File not found: mainwindow.obj: LNK2019: unresolved external symbol "void __cdecl cv::GaussianBlur(class cv::_InputArray const &,class cv::_OutputArray const &,class cv::Size_<int>,double,double,int)" (?GaussianBlur@cv@@YAXAEBV_InputArray@1@AEBV_OutputArray@1@V?$Size_@H@1@NNH@Z) referenced in function "private: void __cdecl MainWindow::on_outputPushButton_pressed(void)" (?on_outputPushButton_pressed@MainWindow@@AEAAXXZ)

LNK1120: 2 unresolved externals release\Hello_Qt_OpenCV.exe:-1: error

I tried clean, run qmake and build as suggested here: https://stackoverflow.com/questions/15864177/file-not-found-mainwindow-obj, but still cannot solve these issues.

trying to build project from chapter 8 MultithreadedCV in QtCreator under Archlinux I got :

/usr/bin/uic ../MultithreadedCV/mainwindow.ui -o ui_mainwindow.h
g++ -c -pipe -g -Wall -W -D_REENTRANT -fPIC -DQT_DEPRECATED_WARNINGS -DQT_QML_DEBUG -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I../MultithreadedCV -I. -isystem /usr/local/include/opencv -isystem /usr/local/include -isystem /usr/include/qt -isystem /usr/include/qt/QtWidgets -isystem /usr/include/qt/QtGui -isystem /usr/include/qt/QtCore -I. -isystem /usr/include/libdrm -I. -I/usr/lib/qt/mkspecs/linux-g++ -o main.o ../MultithreadedCV/main.cpp
../MultithreadedCV/main.cpp:26:16: error: stray ‘\342’ in program
         return “”;
                ^
../MultithreadedCV/main.cpp:26:17: error: stray ‘\200’ in program
         return “”;
                 ^
../MultithreadedCV/main.cpp:26:18: error: stray ‘\234’ in program
         return “”;
                  ^
../MultithreadedCV/main.cpp:26:19: error: stray ‘\342’ in program
         return “”;
                   ^
../MultithreadedCV/main.cpp:26:20: error: stray ‘\200’ in program
         return “”;
                    ^
../MultithreadedCV/main.cpp:26:21: error: stray ‘\235’ in program
         return “”;
                     ^
../MultithreadedCV/main.cpp:32:31: error: stray ‘\342’ in program
                       QString(“\”).toStdWString().c_str(),
                               ^
../MultithreadedCV/main.cpp:32:32: error: stray ‘\200’ in program
                       QString(“\”).toStdWString().c_str(),
                                ^
../MultithreadedCV/main.cpp:32:33: error: stray ‘\234’ in program
                       QString(“\”).toStdWString().c_str(),
                                 ^
../MultithreadedCV/main.cpp:32:34: error: stray ‘\’ in program
                       QString(“\”).toStdWString().c_str(),
                                  ^
../MultithreadedCV/main.cpp:32:35: error: stray ‘\342’ in program
                       QString(“\”).toStdWString().c_str(),
                                   ^
../MultithreadedCV/main.cpp:32:36: error: stray ‘\200’ in program
                       QString(“\”).toStdWString().c_str(),
                                    ^
../MultithreadedCV/main.cpp:32:37: error: stray ‘\235’ in program
                       QString(“\”).toStdWString().c_str(),
                                     ^
../MultithreadedCV/main.cpp: In function ‘QString getVersionString(QString)’:
../MultithreadedCV/main.cpp:18:5: error: ‘DWORD’ was not declared in this scope
     DWORD dwHandle;
     ^~~~~
../MultithreadedCV/main.cpp:19:11: error: expected ‘;’ before ‘dwLen’
     DWORD dwLen = GetFileVersionInfoSize(fName.toStdWString().c_str(), &dwHandle);
           ^~~~~
../MultithreadedCV/main.cpp:21:5: error: ‘LPVOID’ was not declared in this scope
     LPVOID lpData = new BYTE[dwLen];
     ^~~~~~
../MultithreadedCV/main.cpp:22:58: error: ‘dwHandle’ was not declared in this scope
     if(!GetFileVersionInfo(fName.toStdWString().c_str(), dwHandle, dwLen, lpData))
                                                          ^~~~~~~~
../MultithreadedCV/main.cpp:22:58: note: suggested alternative: ‘drand48’
     if(!GetFileVersionInfo(fName.toStdWString().c_str(), dwHandle, dwLen, lpData))
                                                          ^~~~~~~~
                                                          drand48
../MultithreadedCV/main.cpp:22:68: error: ‘dwLen’ was not declared in this scope
     if(!GetFileVersionInfo(fName.toStdWString().c_str(), dwHandle, dwLen, lpData))
                                                                    ^~~~~
../MultithreadedCV/main.cpp:22:75: error: ‘lpData’ was not declared in this scope
     if(!GetFileVersionInfo(fName.toStdWString().c_str(), dwHandle, dwLen, lpData))
                                                                           ^~~~~~
../MultithreadedCV/main.cpp:22:75: note: suggested alternative: ‘QMapData’
     if(!GetFileVersionInfo(fName.toStdWString().c_str(), dwHandle, dwLen, lpData))
                                                                           ^~~~~~
                                                                           QMapData
../MultithreadedCV/main.cpp:22:9: error: ‘GetFileVersionInfo’ was not declared in this scope
     if(!GetFileVersionInfo(fName.toStdWString().c_str(), dwHandle, dwLen, lpData))
         ^~~~~~~~~~~~~~~~~~
../MultithreadedCV/main.cpp:25:18: error: type ‘<type error>’ argument given to ‘delete’, expected pointer
         delete[] lpData;
                  ^~~~~~
../MultithreadedCV/main.cpp:26:9: error: return-statement with no value, in function returning ‘QString’ [-fpermissive]
         return “”;
         ^~~~~~
../MultithreadedCV/main.cpp:29:5: error: ‘VS_FIXEDFILEINFO’ was not declared in this scope
     VS_FIXEDFILEINFO *lpBuffer = NULL;
     ^~~~~~~~~~~~~~~~
../MultithreadedCV/main.cpp:29:23: error: ‘lpBuffer’ was not declared in this scope
     VS_FIXEDFILEINFO *lpBuffer = NULL;
                       ^~~~~~~~
../MultithreadedCV/main.cpp:29:23: note: suggested alternative: ‘setbuffer’
     VS_FIXEDFILEINFO *lpBuffer = NULL;
                       ^~~~~~~~
                       setbuffer
../MultithreadedCV/main.cpp:30:5: error: ‘UINT’ was not declared in this scope
     UINT uLen;
     ^~~~
../MultithreadedCV/main.cpp:30:5: note: suggested alternative: ‘MIN’
     UINT uLen;
     ^~~~
     MIN
../MultithreadedCV/main.cpp:31:23: error: ‘lpData’ was not declared in this scope
     if(!VerQueryValue(lpData,
                       ^~~~~~
../MultithreadedCV/main.cpp:31:23: note: suggested alternative: ‘QMapData’
     if(!VerQueryValue(lpData,
                       ^~~~~~
                       QMapData
../MultithreadedCV/main.cpp:33:31: error: expected primary-expression before ‘)’ token
                       (LPVOID*)&lpBuffer,
                               ^
../MultithreadedCV/main.cpp:34:24: error: ‘uLen’ was not declared in this scope
                       &uLen))
                        ^~~~
../MultithreadedCV/main.cpp:34:24: note: suggested alternative: ‘QPen’
                       &uL``en))
                        ^~~~
                        QPen
../MultithreadedCV/main.cpp:31:9: error: ‘VerQueryValue’ was not declared in this scope
     if(!VerQueryValue(lpData,
         ^~~~~~~~~~~~~
../MultithreadedCV/main.cpp:42:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^
make: *** [Makefile:603: main.o] Error 1
16:51:15: The process "/usr/bin/make" exited with code 2.
Error while building/deploying project MultithreadedCV (kit: Desktop)
When executing step "Make"
16:51:15: Elapsed time: 00:03.

Undefined symbols for architecture x86_64:
"cv::medianBlur(cv::_InputArray const&, cv::_OutputArray const&, int)", referenced from:
MainWindow::on_outputPushButton_pressed() in mainwindow.o
"cv::GaussianBlur(cv::_InputArray const&, cv::OutputArray const&, cv::Size, double, double, int)", referenced from:
MainWindow::on_outputPushButton_pressed() in mainwindow.o
"cv::Mat::deallocate()", referenced from:
cv::Mat::release() in mainwindow.o
"cv::String::deallocate()", referenced from:
cv::String::~String() in main.o
cv::String::operator=(cv::String const&) in main.o
cv::String::~String() in mainwindow.o
cv::String::operator=(cv::String const&) in mainwindow.o
cv::String::~String() in moc_mainwindow.o
cv::String::operator=(cv::String const&) in moc_mainwindow.o
"cv::String::allocate(unsigned long)", referenced from:
cv::String::String(std::__1::basic_string<char, std::__1::char_traits, std::__1::allocator > const&) in mainwindow.o
cv::String::String(char const*) in mainwindow.o
"cv::imread(cv::String const&, int)", referenced from:
MainWindow::on_outputPushButton_pressed() in mainwindow.o
"cv::imshow(cv::String const&, cv::_InputArray const&)", referenced from:
MainWindow::on_outputPushButton_pressed() in mainwindow.o
"cv::imwrite(cv::String const&, cv::_InputArray const&, std::__1::vector<int, std::__1::allocator > const&)", referenced from:
MainWindow::on_outputPushButton_pressed() in mainwindow.o
"cv::fastFree(void*)", referenced from:
cv::Mat::operator=(cv::Mat&&) in mainwindow.o
cv::Mat::~Mat() in mainwindow.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [Hello_Qt_OpenCV.app/Contents/MacOS/Hello_Qt_OpenCV] Error 1
17:36:19: 进程"/usr/bin/make"退出，退出代码 2 。
Error while building/deploying project Hello_Qt_OpenCV (kit: Desktop Qt 5.9.1 clang 64bit)
When executing step "Make"
17:36:19: Elapsed time: 00:07.

OS: Macbook pro 10.14
QT Creator: 5.9.1
Opencv version: 3.3.1

Error message:

libc++abi.dylib: terminating with uncaught exception of type cv::Exception: OpenCV(3.4.3) /Users/tomihasa/Downloads/opencv-3.4.3/modules/imgproc/src/color.hpp:255: error: (-2:Unspecified error) in function 'cv::CvtHelper<cv::Set<1, -1, -1>, cv::Set<3, 4, -1>, cv::Set<0, 2, 5>, cv::SizePolicy::NONE>::CvtHelper(InputArray, OutputArray, int) [VScn = cv::Set<1, -1, -1>, VDcn = cv::Set<3, 4, -1>, VDepth = cv::Set<0, 2, 5>, sizePolicy = cv::SizePolicy::NONE]'

Invalid number of channels in input image:
'VScn::contains(scn)'
where
'scn' is 3

Instead of using line:

cvtColor(inputImage, outputImage, CV_GRAY2RGBA);

Use line:

cvtColor(inputImage, outputImage, CV_32FC(1));

for example :https://github.com/PacktPublishing/Computer-Vision-with-OpenCV-3-and-Qt5/blob/master/ch08/MultithreadedCV/main.cpp#L18-L21

fail to build on Archlinux and certainly also on Mac OS