Size of an Icon

[LordQt]

Hello Friends.
How can I modify the size of my icon in my QListWidgetItem. I have an png with 128*128

QStringList myStringList2;
	myStringList2 <<"test";
	QIcon testItemIcon(":/images/undo.png");
	foreach(QString str2, myStringList2){
		QListWidgetItem *testItem = new QListWidgetItem(testItemIcon, str2, customerList);
		customerList->addItem(testItem);
		QRadialGradient gradient(100, 100, 100, 100, 100);
   		gradient.setColorAt(0, QColor::fromRgbF(210, 239, 109,0));
   		gradient.setColorAt(1, QColor::fromRgbF(0, 1, 0, 0)); 
   		QBrush brush(gradient);
		testItem->setBackground(brush);
	}

QStringList myStringList2;
	myStringList2 <<"test";
	QIcon testItemIcon(":/images/undo.png");
	foreach(QString str2, myStringList2){
		QListWidgetItem *testItem = new QListWidgetItem(testItemIcon, str2, customerList);
		customerList->addItem(testItem);
		QRadialGradient gradient(100, 100, 100, 100, 100);
   		gradient.setColorAt(0, QColor::fromRgbF(210, 239, 109,0));
   		gradient.setColorAt(1, QColor::fromRgbF(0, 1, 0, 0)); 
   		QBrush brush(gradient);
		testItem->setBackground(brush);
	}

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but my icon is quit little and i don´t know why??

Have you some ideas