diff --git a/src/data/pointcalculate.cpp b/src/data/pointcalculate.cpp
index 5a1437b..d13af3b 100644
--- a/src/data/pointcalculate.cpp
+++ b/src/data/pointcalculate.cpp
@@ -184,6 +184,7 @@ void PointCalculate::setRegionPointX(const float left, const float right)
     _rightSelectedPoint = getClosestPointByX(right);
 
     _peakPoint = getPeakPoint();
+
     logde<<"peak point:"<<_peakPoint.x()<<","<<_peakPoint.y();
 
     //根据峰谷重置选择点。
@@ -197,7 +198,8 @@ QVector<QPointF> PointCalculate::getPeakPointGroup()
 {
     QVector<QPointF> pointVtr;
     for(FileManager::ExperimentData& ed:_dataVtr)   {
-        if(ed.sampleTemp >= _leftSelectedPoint.x() && ed.sampleTemp <= _rightSelectedPoint.x()){
+        if(ed.sampleTemp >= _leftSelectedPoint.x() &&
+                ed.sampleTemp <= _rightSelectedPoint.x()){
             pointVtr.push_back(QPointF(ed.sampleTemp,ed.dsc));
         }
     }
@@ -205,7 +207,7 @@ QVector<QPointF> PointCalculate::getPeakPointGroup()
     return pointVtr;
 }
 
-double PointCalculate::calculateArea() {
+float PointCalculate::calculateArea() {
     //getPoint group
     QVector<QPointF> points = getPeakPointGroup();
 
@@ -218,27 +220,27 @@ double PointCalculate::calculateArea() {
     }
 
     //find a line.
-    double k = (_leftSelectedPoint.y() - _rightSelectedPoint.y()) /
+    float k = (_leftSelectedPoint.y() - _rightSelectedPoint.y()) /
             (_leftSelectedPoint.x() - _rightSelectedPoint.x());
-    double b = _leftSelectedPoint.y() - k * _leftSelectedPoint.x();
+    float b = _leftSelectedPoint.y() - k * _leftSelectedPoint.x();
 
     for (size_t i = 0; i < n - 1; ++i) {
 #if 1
-        double x1 = points[i].x();
-        double y1 = points[i].y();
+        float x1 = points[i].x();
+        float y1 = points[i].y();
 
-        double x2 = points[i + 1].x();
-        double y2 = points[i + 1].y();
+        float x2 = points[i + 1].x();
+        float y2 = points[i + 1].y();
 #endif
-        double yLine1 = k * x1 + b;
-        double yLine2  = k * x2 + b;
+        float yLine1 = k * x1 + b;
+        float yLine2  = k * x2 + b;
 
-        double diff1 = y1 - yLine1;
-        double diff2 = y2 - yLine2;
+        float diff1 = y1 - yLine1;
+        float diff2 = y2 - yLine2;
 
-        double dx = x2 - x1;
+        float dx = x2 - x1;
 
-        double cellArea = (diff1 + diff2) * dx /2.0;
+        float cellArea = (diff1 + diff2) * dx /2.0;
 
         integral += std::abs(cellArea);
     }
@@ -289,9 +291,9 @@ void PointCalculate::updateStartEndPoint()
     }
 }
 QString PointCalculate::textFormatPeakPoint(const float enthalpyValue,
-                                       const float peakValue,
-                                       const float startPoint,
-                                       const float endPoint)
+                                            const float peakValue,
+                                            const float startPoint,
+                                            const float endPoint)
 {
     return QString("峰的综合信息：\n"
                    "焓值：%1 J/g \n"
@@ -306,7 +308,7 @@ QString PointCalculate::textFormatPeakPoint(const float enthalpyValue,
 
 // 计算两条直线的交点
 QPointF PointCalculate::calculateIntersection(const QPointF p1,const QPointF p2,
-                                         const QPointF p3, const QPointF p4){
+                                              const QPointF p3, const QPointF p4){
     // 直线的一般式: A1x + B1y + C1 = 0 和 A2x + B2y + C2 = 0
     float A1 = p2.y() - p1.y();
     float B1 = p1.x() - p2.x();
@@ -328,6 +330,44 @@ QPointF PointCalculate::calculateIntersection(const QPointF p1,const QPointF p2,
     }
 }
 
+QPair<float,float> PointCalculate::getCurveInflectionPointTangent(const float x1,const float x2)
+{
+    std::vector<float> dataVtr;
+    for(FileManager::ExperimentData& ed:_dataVtr){
+        if(x1 < ed.sampleTemp && ed.sampleTemp < x2){
+            dataVtr.push_back(ed.sampleTemp);
+        }
+    }
+    //
+    std::vector<float> processedVtr = movingAverage(dataVtr,5);
+
+    // find max slope.
+    float maxSlope = 0.0;
+    float targetX = 0.0;
+    for (size_t i = 1; i < processedVtr.size(); ++i) {
+        float slope = processedVtr[i] - processedVtr[i - 1];
+        if(std::abs(slope) > maxSlope){
+            maxSlope = slope;
+            targetX = processedVtr[i];
+        }
+    }
+
+    // calculate line slope and axis Y space number b.
+    QPointF point = getClosestPointByX(targetX);
+
+    // 使用点斜式方程求y轴截距
+    // y = m * x + b
+    //      double b = y - m * x;
+    float b = point.y() - maxSlope * point.x();
+
+    return qMakePair<float,float>(maxSlope,b);
+}
+QPointF PointCalculate::getIntersectionBySlope(const LineStruct& line1, const LineStruct& line2) {
+    float x = (line2.intercept - line1.intercept) / (line1.slope - line2.slope);
+    float y = line1.slope * x + line1.intercept;
+//    return {x, y};
+    return QPointF(x,y);
+}
 QPointF PointCalculate::getClosestPointByX(const float targetX)
 {
 #if 0
@@ -362,7 +402,7 @@ QPointF PointCalculate::getClosestPointByX(const float targetX)
     if(left > 0 &&
             std::abs(resultPointF.x() - targetX) >
             std::abs(_dataVtr.at(left - 1).sampleTemp - targetX)){
-    //
+        //
         resultPointF = QPointF(_dataVtr.at(left - 1).sampleTemp,
                                _dataVtr.at(left - 1).dsc);
     }
@@ -381,10 +421,11 @@ QString PointCalculate::textFormatNumbericalLabel(const QPointF point)
 QPair<QPointF, QPointF> PointCalculate::getStartAndEndPoint()
 {
     if(_dataVtr.empty()){
-         return qMakePair(QPointF(), QPointF());
+        return qMakePair(QPointF(), QPointF());
     }
-    FileManager::ExperimentData startPoint = _dataVtr.at(0);
-    FileManager::ExperimentData endPoint = _dataVtr.at(_dataVtr.size() - 1);
+
+    FileManager::ExperimentData startPoint  = _dataVtr.at(0);
+    FileManager::ExperimentData endPoint    = _dataVtr.at(_dataVtr.size() - 1);
 
     return qMakePair<QPointF,QPointF>(
                 QPointF(startPoint.sampleTemp,startPoint.dsc),
@@ -405,12 +446,16 @@ QString PointCalculate::textFormatEndPoint(const QPointF point)
                    ).arg(QString::number(point.x(), 'f', 3));
 }
 
-QPair<float,float> PointCalculate::getCurveInflectionPointTangent()
+
+QPointF PointCalculate::getClosestPointByY(const float left,const float right,const float valueY)
 {
-
-}
-
-QVector<QPointF> PointCalculate::getRegionPoints(const float, const float)
-{
-
+    float minValue = 100.0;
+    for(FileManager::ExperimentData& ed:_dataVtr){
+        if(left < ed.sampleTemp && ed.sampleTemp < right){
+            if(std::abs(ed.dsc - valueY) < minValue){
+                return QPointF(ed.sampleTemp,ed.dsc);
+            }
+        }
+    }
+    return QPointF();
 }
diff --git a/src/data/pointcalculate.h b/src/data/pointcalculate.h
index 1a4c81d..b409991 100644
--- a/src/data/pointcalculate.h
+++ b/src/data/pointcalculate.h
@@ -12,7 +12,13 @@ QPair<QPointF,QPointF> getStartAndEndPoint();
 
 void setRegionPointX(const float,const float);
 QPointF getClosestPointByX(const float);
+QPointF getClosestPointByY(const float left,const float right,const float valueY);
 QPointF getPeakPoint();
+
+QPair<QPointF,QPointF> calculateStartAndEndPoint();
+float calculateArea();
+
+// text format
 QString textFormatPeakPoint(const float enthalpyValue,
                    const float peakValue,
                    const float startPoint,
@@ -21,12 +27,14 @@ QString textFormatNumbericalLabel(const QPointF);
 QString textFormatStartPoint(const QPointF);
 QString textFormatEndPoint(const QPointF);
 
-QPair<QPointF,QPointF> calculateStartAndEndPoint();
-double calculateArea();
+// glass transition
+QPair<float,float> getCurveInflectionPointTangent(const float,const float);
+struct LineStruct {
+    float slope; //
+    float intercept; //
+};
+QPointF getIntersectionBySlope(const LineStruct& line1, const LineStruct& line2);
 
-//​获取曲线拐点处的切线
-QPair<float,float> getCurveInflectionPointTangent();
-QVector<QPointF> getRegionPoints(const float,const float);
 //private
 void updateStartEndPoint();
 QPair<QPointF,QPointF> calculateMaxDiffPointLeft();
diff --git a/src/ui/centralwidget.cpp b/src/ui/centralwidget.cpp
index 4bb780a..8859fbd 100644
--- a/src/ui/centralwidget.cpp
+++ b/src/ui/centralwidget.cpp
@@ -231,9 +231,9 @@ void CentralWidget::slotAnalysisSettingApply()
             <<startEndPointPair.second.x();
 
         drawText(peakPoint,PointCalculate::textFormatPeakPoint(enthalpyValue,
-                                                          peakPoint.x(),
-                                                          startEndPointPair.first.x(),
-                                                          startEndPointPair.second.x()));
+                                                               peakPoint.x(),
+                                                               startEndPointPair.first.x(),
+                                                               startEndPointPair.second.x()));
         //
         break;
     }
@@ -322,19 +322,72 @@ void CentralWidget::glassTransitionHandle()
     logde<<"point2:"<<point2.x()<<","<<point2.y();
 
     QCPItemStraightLine *line1 = new QCPItemStraightLine(_customPlot);
-    line1->point1->setCoords(point1.x() - 55,point1.y());
-    line1->point2->setCoords(point1.x() + 55,point1.y());
-    line1->setPen(QPen(Qt::darkGreen));
+    line1->point1->setCoords(point1.x() - 5,point1.y());
+    line1->point2->setCoords(point1.x() + 5,point1.y());
+    line1->setPen(QPen(Qt::darkRed));
     line1->setSelectable(false);
     line1->setVisible(true);
 
     QCPItemStraightLine *line2 = new QCPItemStraightLine(_customPlot);
-    line2->point1->setCoords(point2.x() - 55,point2.y());
-    line2->point2->setCoords(point2.x() + 55,point2.y());
+    line2->point1->setCoords(point2.x() - 5,point2.y());
+    line2->point2->setCoords(point2.x() + 5,point2.y());
     line2->setPen(QPen(Qt::darkGreen));
     line2->setSelectable(false);
     line2->setVisible(true);
 
+    _customPlot->replot();
+    //
+    PointCalculate::LineStruct lineStrc1,lineStrc2,tangetLineStrc;
+
+    lineStrc1.slope = 0.0;
+    lineStrc1.intercept = point1.y();
+
+    lineStrc2.slope = 0.0;
+    lineStrc2.intercept  = point2.y();
+
+    QPair<float,float> tangentLinePair = PointCalculate::getCurveInflectionPointTangent(point1.x(),point2.x());
+    tangetLineStrc.slope = tangentLinePair.first;
+    tangetLineStrc.intercept = tangentLinePair.second;
+
+    QPointF intersection1 = PointCalculate::getIntersectionBySlope(tangetLineStrc,lineStrc1);
+    QPointF intersection2 = PointCalculate::getIntersectionBySlope(tangetLineStrc,lineStrc2);
+
+    //    logde<<"intersection1 x:"<<intersection1.x();
+    //    logde<<"intersection2 x:"<<intersection2.x();
+
+    //
+    float averageY = (point1.y() + point2.y()) /2;
+    QPointF averagePoint = PointCalculate::getClosestPointByY(point1.x(),point2.x(),averageY);
+
+//    logde<<"average y:"<<averageY;
+    logde<<"averagePoint x,y:"<<averagePoint.x()<<","
+        <<averagePoint.y();
+
+    logde<<"glass T1:"<<intersection1.x()
+        <<",Tg:"<<averagePoint.x()
+       <<",T2:"<<intersection2.x();
+
+#if 0
+    // 创建一个圆形绘图项
+    QCPItemEllipse *circle = new QCPItemEllipse(_customPlot);
+//    _customPlot->addItem(circle);
+
+    // 设置圆形的位置和大小
+    circle->topLeft->setCoords(-5, 5);
+    circle->bottomRight->setCoords(5, -5);
+
+    // 设置圆形的填充和边框颜色
+    circle->setBrush(QBrush(Qt::cyan));
+    circle->setPen(QPen(Qt::blue));
+#endif
+
+    QCPItemStraightLine *line3 = new QCPItemStraightLine(_customPlot);
+    line3->point1->setCoords(averagePoint.x() + 2,averagePoint.y() + 2);
+    line3->point2->setCoords(averagePoint.x() - 2,averagePoint.y() - 2);
+    line3->setPen(QPen(Qt::black));
+    line3->setSelectable(false);
+    line3->setVisible(true);
+
     _customPlot->replot();
 }
 
diff --git a/src/ui/centralwidget.h b/src/ui/centralwidget.h
index dea6348..03bf67b 100644
--- a/src/ui/centralwidget.h
+++ b/src/ui/centralwidget.h
@@ -50,6 +50,7 @@ private:
     void setEventHandlerEnable(const bool);
     void drawText(const QPointF,const QString);
     void fillGraph(const double x1,const double x2);
+
     enum ClearDataMode{
         All,
         Undo