diff -r 804fa18e8bc1 qtgui/mainwindow.cpp
--- a/qtgui/mainwindow.cpp	Thu Jan 19 09:44:35 2012 +0100
+++ b/qtgui/mainwindow.cpp	Thu Jan 19 20:20:31 2012 -0700
@@ -49,6 +49,8 @@
 
 #include <QStringListModel>
 
+#include <QFile>
+
 #include "error.h"
 
 #include "mainwindow.hxx"
@@ -887,30 +889,18 @@
 void MainWindow::outputBufferGroupsTonemapped()
 {
 	// Where should these be output
-	QString fileName = QFileDialog::getSaveFileName(this, tr("Select a destination for the images"), m_lastOpendir, tr("PNG Image (*.png);;JPEG Image (*.jpg);;Windows Bitmap (*.bmp);;TIFF Image (*.tif)"));
+	QString fileName = QFileDialog::getSaveFileName(this, tr("Select a destination for the images"), m_lastOpendir, tr("PNG Image (*.png);;JPEG Image (*.jpg);;Windows Bitmap (*.bmp);;TIFF Image (*.tif)"), NULL, QFileDialog::DontConfirmOverwrite);
 	if (fileName.isEmpty())
 		return;
 
-	// Show busy cursor
-	QApplication::setOverrideCursor(QCursor(Qt::WaitCursor));
-
 	// Output the light groups
-	if (saveAllLightGroups(fileName, false)) {
-		statusMessage->setText(tr("Light group tonemapped images saved"));
-		LOG(LUX_INFO, LUX_NOERROR) << "Light group tonemapped images saved to '" << qPrintable(fileName) << "'";
-	} else {
-		statusMessage->setText(tr("ERROR: Light group tonemapped images NOT saved"));
-		LOG(LUX_WARNING, LUX_SYSTEM) << "Error while saving light group tonemapped images to '" << qPrintable(fileName) << "'";
-	}
-
-	// Stop showing busy cursor
-	QApplication::restoreOverrideCursor();
+	saveAllLightGroups(fileName, false);
 }
 
 void MainWindow::outputBufferGroupsHDR()
 {
 	// Where should these be output
-	QString fileName = QFileDialog::getSaveFileName(this, tr("Select a destination for the images"), m_lastOpendir, tr("OpenEXR Image (*.exr)"));
+	QString fileName = QFileDialog::getSaveFileName(this, tr("Select a destination for the images"), m_lastOpendir, tr("OpenEXR Image (*.exr)"), NULL, QFileDialog::DontConfirmOverwrite);
 	if (fileName.isEmpty())
 		return;
 
@@ -923,27 +913,42 @@
 	openExrCompressionType = options->getCompressionType();
 	delete options;
 
-	// Show busy cursor
-	QApplication::setOverrideCursor(QCursor(Qt::WaitCursor));
-
 	// Output the light groups
-	if (saveAllLightGroups(fileName, true)) {
-		statusMessage->setText(tr("Light group HDR images saved"));
-		LOG(LUX_INFO, LUX_NOERROR) << "Light group HDR images saved to '" << qPrintable(fileName) << "'";
-	} else {
-		statusMessage->setText(tr("ERROR: Light group HDR images NOT saved"));
-		LOG(LUX_WARNING, LUX_SYSTEM) << "Error while saving light group HDR images to '" << qPrintable(fileName) << "'";
-	}
-
-	// Stop showing busy cursor
-	QApplication::restoreOverrideCursor();
+	saveAllLightGroups(fileName, true);
 }
 
 bool MainWindow::saveAllLightGroups(const QString &outFilename, const bool &asHDR)
 {
+	// Prepare filename (will hack up when outputting each light group)
+	boost::filesystem::path filenamePath(qPrintable(outFilename));
+
 	// Get number of light groups
 	int lgCount = (int)luxGetParameterValue(LUX_FILM, LUX_FILM_LG_COUNT);
 
+	// Check if output files already exist
+	for(int i=0; i<lgCount; i++)
+	{
+		// Get light group name
+		char lgName[256];
+		luxGetStringParameterValue(LUX_FILM, LUX_FILM_LG_NAME, lgName, 256, i);
+
+		// Generate output file name
+		QString outputName = QString("%1/%2-%3%4").arg(filenamePath.parent_path().string().c_str())
+			.arg(filenamePath.stem().c_str()).arg(lgName).arg(filenamePath.extension().c_str());
+
+		// Check if file exists
+		if (QFile::exists(outputName))
+		{
+			// File exists - ask user if existing files should be overwritten
+			if (QMessageBox::warning(this, tr("Confirm Save As"),tr("Light group files already exist.\nDo you want to replace them?"), QMessageBox::Yes|QMessageBox::No, QMessageBox::No) == QMessageBox::No)
+				return false;
+			break;
+		}
+	}
+
+	// Show busy cursor
+	QApplication::setOverrideCursor(QCursor(Qt::WaitCursor));
+
 	// Start by save current light group state and turning off ALL light groups
 	vector<bool> prevLGState(lgCount);
 	for(int i=0; i<lgCount; i++)
@@ -952,9 +957,6 @@
 		luxSetParameterValue(LUX_FILM, LUX_FILM_LG_ENABLE, 0.f, i);
 	}
 
-	// Prepare filename (will hack up when outputting each light group)
-	boost::filesystem::path filenamePath(qPrintable(outFilename));
-
 	// Get film resolution (only needed for tonemapped case but better off being outside loop)
 	int w = luxGetIntAttribute("film", "xResolution");
 	int h = luxGetIntAttribute("film", "yResolution");
@@ -1001,6 +1003,21 @@
 	if (!asHDR)
 		luxUpdateFramebuffer();
 
+	// Report on success or failure
+	QString outputName = QString("%1/%2-*%4").arg(filenamePath.parent_path().string().c_str())
+		.arg(filenamePath.stem().c_str()).arg(filenamePath.extension().c_str());
+
+	if (result) {
+		statusMessage->setText(tr("Light group images saved"));
+		LOG(LUX_INFO, LUX_NOERROR) << "Light group images saved to '" << qPrintable(outputName) << "'";
+	} else {
+		statusMessage->setText(tr("ERROR: Light group images NOT saved"));
+		LOG(LUX_WARNING, LUX_SYSTEM) << "Error while saving light group images to '" << qPrintable(outputName) << "'";
+	}
+
+	// Stop showing busy cursor
+	QApplication::restoreOverrideCursor();
+
 	// Report success or failure (always success when outputting HDR)
 	return result;
 }