Storage and View -> imageViewer

[C167]

okay, i wrote a little testapp that stores an image (or every file you give it) into a BLOB-field. the db-file grows to the size of the given image, so it should be in it, although the chars i get if i do a select to qDebug() are only 8, all unprintable. So, here's my app:

int main( int argc, char *argv[] )
{
	QCoreApplication app( argc, argv );
	QSqlDatabase db = QSqlDatabase::addDatabase( "QSQLITE" );
	db.setDatabaseName( "/home/stefan/source/qt4/cdlauncher/pictures.db" );
	if ( !db.open() )
	{
		qDebug() << "Opening failed";
		return 1;
	}
	qDebug() << "Opening successfull, using database " << db.databaseName();
	qDebug() << "filling an image into the DB...";
	QFile file( "/home/stefan/pic/space/191853main_image_feature_929_full.jpg" );
	QByteArray fileData;
	if ( file.exists() )
	{
		if ( file.open( QIODevice::ReadOnly ) )
		{
			fileData = file.readAll();
			file.close();
		}
	}
	else
	{
		qDebug() << "File " << file.fileName() << " could not be located";
	}
	QSqlQuery query("UPDATE pictures SET data=? WHERE rowid=1;");
	query.addBindValue(fileData);
	query.exec();
	qDebug() << query.lastError();
	return 0;
}

int main( int argc, char *argv[] )
{
	QCoreApplication app( argc, argv );
	QSqlDatabase db = QSqlDatabase::addDatabase( "QSQLITE" );
	db.setDatabaseName( "/home/stefan/source/qt4/cdlauncher/pictures.db" );
	if ( !db.open() )
	{
		qDebug() << "Opening failed";
		return 1;
	}
	qDebug() << "Opening successfull, using database " << db.databaseName();
	qDebug() << "filling an image into the DB...";
	QFile file( "/home/stefan/pic/space/191853main_image_feature_929_full.jpg" );
	QByteArray fileData;
	if ( file.exists() )
	{
		if ( file.open( QIODevice::ReadOnly ) )
		{
			fileData = file.readAll();
			file.close();
		}
	}
	else
	{
		qDebug() << "File " << file.fileName() << " could not be located";
	}
	QSqlQuery query("UPDATE pictures SET data=? WHERE rowid=1;");
	query.addBindValue(fileData);
	query.exec();
	qDebug() << query.lastError();
	return 0;
}

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that works everything is hardcoded, i know, but its only a test to see how it works.
So, now i want to retrieve the data. the normal way to display an image is

imgLabel->setPixmap(QPixmap::fromImage(QImage("filename")));

imgLabel->setPixmap(QPixmap::fromImage(QImage("filename")));

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After some testing, reading and coffee-ing, i found the following way:

int main( int argc, char *argv[] )
{
	Q_INIT_RESOURCE( application );
	QApplication app( argc, argv );
	QSqlDatabase db = QSqlDatabase::addDatabase( "QSQLITE" );
	db.setDatabaseName( "/home/stefan/source/qt4/cdlauncher/pictures.db" );
	if ( !db.open() )
	{
		qDebug() << "Opening failed";
		return 1;
	}
	QSqlQuery query( "SELECT data FROM pictures WHERE rowid=1;" );
	QSqlRecord record = query.record();
	query.next();
	qDebug() << query.lastError();
	QByteArray ba = query.value(0).toByteArray();
	QWidget *wid = new QWidget();
	QLabel *imgLabel = new QLabel( wid );
	QPixmap *pic = new QPixmap();
	pic->loadFromData( query.value( record.indexOf( "data" ) ).toByteArray() );
	imgLabel->setPixmap( *pic );
	wid->show();
	return app.exec();
}

int main( int argc, char *argv[] )
{
	Q_INIT_RESOURCE( application );
	QApplication app( argc, argv );
	QSqlDatabase db = QSqlDatabase::addDatabase( "QSQLITE" );
	db.setDatabaseName( "/home/stefan/source/qt4/cdlauncher/pictures.db" );
	if ( !db.open() )
	{
		qDebug() << "Opening failed";
		return 1;
	}
	QSqlQuery query( "SELECT data FROM pictures WHERE rowid=1;" );
	QSqlRecord record = query.record();
	query.next();
	qDebug() << query.lastError();
	QByteArray ba = query.value(0).toByteArray();
	QWidget *wid = new QWidget();
	QLabel *imgLabel = new QLabel( wid );
	QPixmap *pic = new QPixmap();
	pic->loadFromData( query.value( record.indexOf( "data" ) ).toByteArray() );
	imgLabel->setPixmap( *pic );
	wid->show();
	return app.exec();
}

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it successfully reads out the image and displays it...
a SELECT-query seems not to like the QSqlQuery::exec () method. So i used a single next() for that...
So far, everything is fantastic, thank you very much Thomas and jacek

[Thomas]

One last issue.

Make sure you delete stuff which you created with new.

[jacek]

a SELECT-query seems not to like the QSqlQuery::exec () method.

If you pass a string to QSqlQuery constructor, it will execute it immediately. It should be:

QSqlQuery query;
query.prepare("UPDATE pictures SET data=? WHERE rowid=1;");
query.addBindValue(fileData);
query.exec();

QSqlQuery query;
query.prepare("UPDATE pictures SET data=? WHERE rowid=1;");
query.addBindValue(fileData);
query.exec();

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And the select should be:

QSqlQuery query( "SELECT data FROM pictures WHERE rowid=1;" );
query.next(); // <- positions the query on the first row
QSqlRecord record = query.record();

QSqlQuery query( "SELECT data FROM pictures WHERE rowid=1;" );
query.next(); // <- positions the query on the first row
QSqlRecord record = query.record();

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[C167]

If you pass a string to QSqlQuery constructor, it will execute it immediately. It should be:

QSqlQuery query;
query.prepare("UPDATE pictures SET data=? WHERE rowid=1;");
query.addBindValue(fileData);
query.exec();

QSqlQuery query;
query.prepare("UPDATE pictures SET data=? WHERE rowid=1;");
query.addBindValue(fileData);
query.exec();

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And the select should be:

QSqlQuery query( "SELECT data FROM pictures WHERE rowid=1;" );
query.next(); // <- positions the query on the first row
QSqlRecord record = query.record();

QSqlQuery query( "SELECT data FROM pictures WHERE rowid=1;" );
query.next(); // <- positions the query on the first row
QSqlRecord record = query.record();

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Okay, thank you

One last issue.
Make sure you delete stuff which you created with new.

I thought Qt is handling such things for all the classes that inherit QObject, at least their own stuff? Okay, thx I'll add everything to my destructors

[jacek]

I thought Qt is handling such things for all the classes that inherit QObject, at least their own stuff?

Yes, it does, but only for objects that have a parent.

[C167]

okay, thx