diff --git a/src/ScanFormWidget.cpp b/src/ScanFormWidget.cpp
index 8950727..75e29c3 100644
--- a/src/ScanFormWidget.cpp
+++ b/src/ScanFormWidget.cpp
@@ -132,6 +132,31 @@ ScanFormWidget::ScanFormWidget(QWidget *parent) : TabFormWidget(parent) {
     });
     connect(EventCenter::Default(),&EventCenter::ResponsePreview,[=](QObject* sender,QObject* data){
         setPreviewing(true);
+        static const size_t Row = 140;
+        static const size_t Col = 140;
+        static const float pixelSpacing = 1.5f;
+        static const float halfROIWidth = 100.0f;
+        uchar c_data[Row][Col];
+        uchar* data_ptr = c_data[0];
+        for(int i=0;i<Row;i++){
+            data_ptr = c_data[i];
+            memset(data_ptr,0,Col);
+        }
+        QImage img(c_data[0] , Col, Row, QImage::Format_Grayscale8);
+        viewer->setFixedSize(800,800);
+        QPixmap pic = QPixmap::fromImage(img).scaledToHeight(800,Qt::SmoothTransformation);
+        QPainter painter(&pic);
+        QPen pen;
+        pen.setStyle(Qt::DashLine);
+        pen.setWidth(3);
+        QFont font("Futura");
+        font.setPixelSize(26);
+        font.setBold(true);
+        painter.setFont(font);
+        pen.setColor(QColor(255,255,0));
+        painter.setPen(pen);
+        painter.drawText(400-13*5,400+13,"Loading...");
+        viewer->setPixmap(pic);
     });
 
     connect(EventCenter::Default(),&EventCenter::ResponsePreviewData,[=](QObject* sender,QObject* data){
@@ -202,6 +227,7 @@ ScanFormWidget::ScanFormWidget(QWidget *parent) : TabFormWidget(parent) {
     connect(group, SIGNAL(buttonClicked(int)),this,SLOT(protocolChanged(int)));
 
     previewfunc = [=](bool val)->void{
+        viewer->setVisible(val);
         btnPreview->setCheckable(val);
         btnPreview->setChecked(val);
         btnPreview->setEnabled(!val);