fixed memory leak in thresholding

app/Operations/ThresholdDialog.cpp

@@ -71,8 +71,10 @@ void ThresholdDialog::updatePreview(){
         else {
             algo = new Binarization_t<GrayscaleImage::depth_t>(_spinbox1->value());
         }
-
-        _preview->setImage(algo->operator()(_image));
+        _previewImage = algo->operator()(_image);
+        _preview->setImage(_previewImage);
+        delete algo;
+        delete _previewImage;
         _preview->repaint();
     }
 

app/Operations/ThresholdDialog.h

@@ -64,6 +64,7 @@ class ThresholdDialog : public QDialog {
     QRadioButton* _blackButton;
     QCheckBox *_doubleBox, *_previewBox;
     ImageWidget* _preview;
+    imagein::GrayscaleImage* _previewImage;
 };
 
 #endif //!THRESHOLDDIALOG_H

app/Operations/ThresholdOp.cpp

@@ -40,5 +40,6 @@ void ThresholdOp::operator()(const imagein::Image* image, const std::map<const i
     }
 
     GrayscaleImage* resImg = algo->operator()(img);
+    delete algo;
     this->outImage(resImg);
 }