Add ability to set param of stretch

image.frag

@@ -24,7 +24,10 @@ void main(void)
         color = log(a*color + 1.0) / log(vec4(a+1));
         break;
     case 4:
-        color = asinh(color / a) / asinh(1 / a);
+    {
+        float l = color.r*0.2126f + color.g*0.7152f + color.b*0.7152f;
+        color *= asinh(l / a) / asinh(1 / a);
+    }
         break;
     }
 

imagescrollareagl.cpp

@@ -111,6 +111,12 @@ void ImageWidget::setStrech(int stretch)
     update();
 }
 
+void ImageWidget::setStretchParam(float param)
+{
+    m_param = param;
+    update();
+}
+
 void ImageWidget::setOffset(int dx, int dy)
 {
     m_dx = dx;
@@ -137,7 +143,7 @@ void ImageWidget::paintGL()
     m_program->setUniformValue("viewport", (float)width(), (float)height());
     m_program->setUniformValue("offset", dx, dy);
     m_program->setUniformValue("stretch", m_stretch);
-    m_program->setUniformValue("a", 0.1f);
+    m_program->setUniformValue("a", m_param);
     m_program->setUniformValue("zoom", 1.0f/m_scale);
 
     m_image->bind(0);

imagescrollareagl.h

@@ -37,6 +37,7 @@ class ImageWidget : public QOpenGLWidget
     float m_range;
     float m_dx, m_dy;
     float m_scale;
+    float m_param;
     bool m_blockRepaint;
 public:
     explicit ImageWidget(QWidget *parent = nullptr);
@@ -49,6 +50,7 @@ public slots:
     void setLow(int low);
     void setHigh(int high);
     void setStrech(int stretch);
+    void setStretchParam(float param);
     void setOffset(int dx, int dy);
 protected:
     void paintGL();

mainwindow.cpp

@@ -52,6 +52,7 @@ MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
     connect(stretchPanel, SIGNAL(lowChanged(int)), m_imageGL->imageWidget(), SLOT(setLow(int)));
     connect(stretchPanel, SIGNAL(highChanged(int)), m_imageGL->imageWidget(), SLOT(setHigh(int)));
     connect(stretchPanel, SIGNAL(stretchChanged(int)), m_imageGL->imageWidget(), SLOT(setStrech(int)));
+    connect(stretchPanel, SIGNAL(paramChanged(float)), m_imageGL->imageWidget(), SLOT(setStretchParam(float)));
 
     QDockWidget *stretchDock = new QDockWidget(tr("Stretch"), this);
     stretchDock->setWidget(stretchPanel);

stretchpanel.cpp

@@ -1,6 +1,5 @@
 #include "stretchpanel.h"
 #include <QVBoxLayout>
-#include <QComboBox>
 
 StretchPanel::StretchPanel(QWidget *parent) : QWidget(parent)
 {
@@ -9,19 +8,45 @@ StretchPanel::StretchPanel(QWidget *parent) : QWidget(parent)
 
     m_lowSlider = new QSlider(Qt::Horizontal, this);
     m_highSlider = new QSlider(Qt::Horizontal, this);
+    m_paramSlider = new QSlider(Qt::Horizontal, this);
 
     m_lowSlider->setRange(0, UINT16_MAX);
     m_highSlider->setRange(0, UINT16_MAX);
     m_highSlider->setValue(UINT16_MAX);
+    m_paramSlider->setRange(0, UINT16_MAX);
 
-    QComboBox *stretchSelect = new QComboBox(this);
-    stretchSelect->addItems({tr("Linear"), tr("Square root"), tr("Power"), tr("Logarithm"), tr("Asinh")});
+    m_stretchSelect = new QComboBox(this);
+    m_stretchSelect->addItems({tr("Linear"), tr("Square root"), tr("Power"), tr("Logarithm"), tr("Asinh")});
 
     layout->addWidget(m_lowSlider);
     layout->addWidget(m_highSlider);
-    layout->addWidget(stretchSelect);
+    layout->addWidget(m_paramSlider);
+    layout->addWidget(m_stretchSelect);
 
     connect(m_lowSlider, SIGNAL(valueChanged(int)), this, SIGNAL(lowChanged(int)));
     connect(m_highSlider, SIGNAL(valueChanged(int)), this, SIGNAL(highChanged(int)));
-    connect(stretchSelect, SIGNAL(activated(int)), this, SIGNAL(stretchChanged(int)));
+    connect(m_paramSlider, SIGNAL(valueChanged(int)), this, SLOT(calculateParam()));
+    connect(m_stretchSelect, SIGNAL(activated(int)), this, SIGNAL(stretchChanged(int)));
+    connect(m_stretchSelect, SIGNAL(activated(int)), this, SLOT(calculateParam()));
+}
+
+void StretchPanel::calculateParam()
+{
+    float val = m_paramSlider->value();
+    float param;
+    switch(m_stretchSelect->currentIndex())
+    {
+    case 2:
+        param = val*10/UINT16_MAX;
+        break;
+    case 3:
+        param = val;
+        break;
+    case 4:
+        param = 1.001-val/UINT16_MAX;
+        break;
+    default:
+        return;
+    }
+    emit paramChanged(param);
 }

stretchpanel.h

@@ -3,18 +3,24 @@
 
 #include <QWidget>
 #include <QSlider>
+#include <QComboBox>
 
 class StretchPanel : public QWidget
 {
     Q_OBJECT
     QSlider *m_lowSlider;
     QSlider *m_highSlider;
+    QSlider *m_paramSlider;
+    QComboBox *m_stretchSelect;
 public:
     explicit StretchPanel(QWidget *parent = nullptr);
 signals:
     void lowChanged(int low);
     void highChanged(int high);
     void stretchChanged(int stretch);
+    void paramChanged(float param);
+private slots:
+    void calculateParam();
 };
 
 #endif // STRETCHPANEL_H