OpenCV 2.4.7 conflict with Qt 4.8.1 QImage

Question

Ubuntu 12.04, Qt 4.8, OpenCv 2.4.3, PCL 1.6. Developing all via Qt Creator 2.5.2. All in 64 bits version.

I din't faced this issue until now, due to the fact I was dealing with image files in disk via "cv::imread(filename)" and then transferring its data to QImage -> QPixmap -> QLabel. NO problem with that.

Now, I need to load some images into Qt resource files. I created the proper .qrc via Qt Creator, and copied and registered image files in it. Well, If I try to load images from resources, it doesn't work:

QImage qi = QImage(":images/red.jpg");
if (qi.isNull())
{
QMessageBox::warning(this,"hey","hey");
}

Of course, at beginning I was struggling with resource names for an entire day. Until I decided to start other project, and copypasted the resource file, and the code that loads that QImage. In the test project, It works OK. (same computer, same IDE & Environment, but no OpenCV linking). Seeing this, I decided to try this piece of code:

QString fn = QFileDialog::getOpenFileName(this,"Load image");
qi = QImage(fn);
if (qi.isNull())
{
QMessageBox::warning(this,"hey","hey");
}

In original code, this doesn't work! fn is loaded with right filename, but "qi = QImage(fn);" fails. In the Test program, this works as expected.

This is a big problem, because I want to set some icons in windows, and some images for several widgets and QSplashScreen. It's not very acceptable to copy image files into generated binaries folders and load them, assuming user will do nothing with them...

I must point again, that this is NOT a issue with Qt resource filename.

Is there some workaround or idea about this?

PD: I tried QPixmap(":images/red.jpg"); but program fails execution.

PD: Some project settings:

ResFiles.qrc:

<RCC>
<qresource prefix="/">
<file>images/red.png</file>
</qresource>
</RCC>

QOP.proj file:

#-------------------------------------------------
#
# Project created by QtCreator 2013-03-09T23:56:16
#
#-------------------------------------------------

QT += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = QOP
TEMPLATE = app

SOURCES += main.cpp\
mainwindow.cpp \
[several files more...]

HEADERS += mainwindow.h \
[several files more...]

FORMS += mainwindow.ui \
camwindow.ui \
dialogsetupcam.ui \
dialogtestcam_sr4k.ui \
dialogtestcam_pmdnano.ui \
dialogcommand_pmdnano.ui \
dialogcreatecam.ui

CONFIG += link_pkgconfig
PKGCONFIG += opencv

CONFIG += link_pkgconfig
PKGCONFIG +=

#Do not use this configuration to get PCL, some sublibraries aren't properly accesible, in example Visualizer
#CONFIG += link_pkgconfig
#PKGCONFIG += pcl_io-1.6

#PCL Headers
INCLUDEPATH += /usr/include/pcl-1.6\
/usr/include/flann/\
/usr/include/eigen3/\
/usr/include/openni/
#PCL Libraries
LIBS += -lpcl_common\
-lpcl_features\
-lpcl_filters\
-lpcl_geometry\
-lpcl_io\
-lpcl_kdtree\
-lpcl_keypoints\
-lpcl_octree\
-lpcl_registration\
-lpcl_sample_consensus\
-lpcl_search\
-lpcl_segmentation\
-lpcl_surface\
-lpcl_tracking\
-lpcl_visualization

#VTK Headers
INCLUDEPATH += /usr/include/vtk-5.8
#VTK Libraries
LIBS += -lQVTK\
-lvtkalglib\
-lvtkCharts\
-lvtkCommon\
-lvtkDICOMParser\
-lvtkexoIIc\
-lvtkFiltering\
-lvtkftgl\
-lvtkGenericFiltering\
-lvtkGeovis\
-lvtkGraphics\
-lvtkHybrid\
-lvtkImaging\
-lvtkInfovis\
-lvtkIO\
-lvtkmetaio\
-lvtkParallel\
-lvtkproj4\
-lvtkQtChart\
-lvtkRendering\
-lvtksys\
-lvtkverdict\
-lvtkViews\
-lvtkVolumeRendering\
-lvtkWidgets

RESOURCES += \
ResFiles.qrc

OTHER_FILES += \
images/red.png

A workaround I've thought is to load these images with some QFile class and "transfer" it to QImage. Can this be done?

Answer 1

I've solved this question this way:

//This WON'T WORK due to problems caused by presence of OpenCV library; it interferes with normal QImage loading from QResources
/*
QImage logoImage(":/images/Logo.png");
*/
//Read file rawly into RAM (workaround to OpenCV/QImage issue)
bool isImageInRAM = false;
QFile       file(":/images/Logo.png"); //Apparently there's no difference between ":/images/QOPLogo.png" and ":images/Logo.png"
QByteArray  rawImageFileInRAM;
if (file.open(QIODevice::ReadOnly))
{
    rawImageFileInRAM = file.readAll();
    file.close();
    isImageInRAM = true;
}
else
    checkFailed(0,QObject::tr("Error loading image from resource: %1").arg(QObject::tr("Logo"))); //checkFailed is a custom method that shows message errors

//This WON'T WORK due to problems caused by presence of OpenCV library; it interferes with normal QImage loading from memory (yes, too U_U)
/*
QImage logoImage = QImage::fromData(rawImageFileInRAM);
*/
std::vector<uchar> buffInRAM(rawImageFileInRAM.data(),rawImageFileInRAM.data()+rawImageFileInRAM.size());
cv::Mat imgMatFromRAM = cv::imdecode(cv::Mat(buffInRAM),CV_LOAD_IMAGE_COLOR);
cv::Mat cvRGBLogoImage(imgMatFromRAM.rows,imgMatFromRAM.cols,CV_8UC3);
cv::cvtColor(imgMatFromRAM,cvRGBLogoImage,CV_BGR2RGB); //Convert BGR->RGB
QImage logoImage((const unsigned char*)cvRGBLogoImage.data,cvRGBLogoImage.cols,cvRGBLogoImage.rows,cvRGBLogoImage.step,QImage::Format_RGB888);

//At this point logoImage already has image from resources ¡Yeaahhhh!!