Problems with Qt Concurrent mapped
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I've been trying to create a simple image processing procedure where i have a list of images that needs to be written to the disk and trimmed so here is the code for this function
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static int i=0;
void writeRenderingImage(const QImage &q){QString path(QDir::currentPath().append("/moviePictures")); QString p(path); p.append(QString("/photo%1.png").arg(i++,5,10,QChar('0'))); std::cout<<p.toStdString()<<"\n"; q.save(p,"PNG",10); QString trimCommand("convert -trim "); trimCommand.append(p).append(" ").append(p); system(trimCommand.toStdString().c_str());}
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Since i have this function i have another function wich calls this procedure through the QtConcurrent::mapped utility
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void GraphPrincipal::createMovieAction() {
i=0;
QString path(QDir::currentPath().append("/moviePictures"));
QString command("rm -rf ");
command.append(path).append("/*.png");
system(command.toStdString().c_str());QProgressDialog dialog; dialog.setLabelText(QString("Progressing using %1 thread(s)...").arg(QThread::idealThreadCount())); QFutureWatcher<void> futureWatcher; connect(&futureWatcher;, SIGNAL(finished()), &dialog;, SLOT(reset())); connect(&dialog;, SIGNAL(canceled()), &futureWatcher;, SLOT(cancel())); connect(&futureWatcher;, SIGNAL(progressRangeChanged(int, int)), &dialog;, SLOT(setRange(int, int))); connect(&futureWatcher;, SIGNAL(progressValueChanged(int)), &dialog;, SLOT(setValue(int)));//gsw->getRenderingImages() returns a QList<Qimage> object
QFuture<void> qv=QtConcurrent::mapped(gsw->getRenderingImages(),writeRenderingImage);
futureWatcher.setFuture(qv);
dialog.exec();
futureWatcher.waitForFinished();
}
@So When i try to run this code i get the following error.
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/usr/include/qt4/QtCore/qtconcurrentmapkernel.h: In member function ‘bool QtConcurrent::MappedEachKernel<Iterator, MapFunctor>::runIteration(Iterator, int, QtConcurrent::MappedEachKernel<Iterator, MapFunctor>::T*) [with Iterator = QList<QImage>::const_iterator, MapFunctor = QtConcurrent::FunctionWrapper1<void, const QImage&>, QtConcurrent::MappedEachKernel<Iterator, MapFunctor>::T = void]’:
In file included from /usr/include/qt4/QtCore/qtconcurrentfilterkernel.h:50:0,
from /usr/include/qt4/QtCore/qtconcurrentfilter.h:49,
from /usr/include/qt4/QtCore/QtCore:92,
from /usr/include/qt4/QtGui/QtGui:3,
from GraphPrincipal.h:10,
from GraphPrincipal.cpp:7:
GraphPrincipal.cpp:146:1: instantiated from here
/usr/include/qt4/QtCore/qtconcurrentmapkernel.h:180:9: error: ‘QtConcurrent::MappedEachKernel<QList<QImage>::const_iterator<QImage>, QtConcurrent::FunctionWrapper1<void, const QImage&> >::T*’ is not a pointer-to-object type
/usr/include/qt4/QtCore/qtconcurrentmapkernel.h: In member function ‘bool QtConcurrent::MappedEachKernel<Iterator, MapFunctor>::runIterations(Iterator, int, int, QtConcurrent::MappedEachKernel<Iterator, MapFunctor>::T*) [with Iterator = QList<QImage>::const_iterator, MapFunctor = QtConcurrent::FunctionWrapper1<void, const QImage&>, QtConcurrent::MappedEachKernel<Iterator, MapFunctor>::T = void]’:
@Can some1 tell me what i'm doing wrong i've been reading all the docs i can but can't find no solution. if some1 could help, plz... do it so.
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Ok as far as I understand the source code and the error provided by you the problem resides in this line of code:
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QFuture<void> qv=QtConcurrent::mapped(gsw->getRenderingImages(),writeRenderingImage);
@Its just a guess but I think the two parameters don't fit. As I understand from the compiler error the @gsw->getRenderingImages()@ returns an iterator of type @QList<QImage>::const_iterator<QImage>@ and writeRenderingImage() expects a const reference to an image.
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i Thank u for your answer, but i solved it using pthread instead. I start one thread per picture to work on, than use pthread_join to track the progress of the work being done. Thanks for the answer anyway.
