Rework stretch to use just MTF

image.frag

@@ -2,43 +2,22 @@
 
 uniform sampler2D qt_Texture0;
 varying vec2 qt_TexCoord0;
-uniform vec2 scale;
+uniform vec3 mtf_param;
-uniform float a;
-uniform int stretch;
 uniform bool bw;
 
+vec4 MTF(vec4 x, vec3 m)
+{
+    x = (x - m.x) / (m.z - m.x);
+    x = clamp(x, vec4(0.0), vec4(1.0));
+    return ((m.y - 1) * x) / ((2 * m.y - 1) * x - m.y);
+}
+
 void main(void)
 {
     vec4 color = texture2D(qt_Texture0, qt_TexCoord0);
     if(bw)color = color.rrra;
-    color = color*scale.x + scale.y;
+    color = MTF(color, mtf_param);
-    color = max(color, vec4(0.0f));
 
-    switch(stretch)
-    {
-    case 0:
-        break;
-    case 1:
-       color = sqrt(color);
-       break;
-    case 2:
-        color = pow(color, vec4(a));
-        break;
-    case 3:
-        color = log(a*color + 1.0) / log(vec4(a+1));
-        break;
-    case 4:
-    {
-        //float l = color.r*0.2126f + color.g*0.7152f + color.b*0.0722f;
-        float l = (color.r+color.g+color.b)*0.33333;
-        float k = asinh(l*a)/(l*asinh(a));
-        color *= k;
-    }
-        break;
-    }
-
-    //color = color*scale.x + scale.y;
-    //float color = pow(c, 0.4545);
     if(any(lessThan(qt_TexCoord0, vec2(0.0))) || any(greaterThan(qt_TexCoord0, vec2(1.0))))
         color = vec4(0.0);
     gl_FragColor = color;

imagescrollareagl.cpp

@@ -41,13 +41,13 @@ ImageWidget::ImageWidget(QWidget *parent) : QOpenGLWidget(parent)
     setFocusPolicy(Qt::ClickFocus);
     m_range = UINT16_MAX;
     m_low = 0;
+    m_mid = 0.5;
     m_high = 1;
     m_dx = m_dy = 0;
     m_scale = 1.0f;
     m_blockRepaint = false;
     m_range = UINT16_MAX;
     m_imgWidth = m_imgHeight = -1;
-    m_stretch = 0;
 }
 
 ImageWidget::~ImageWidget()
@@ -67,6 +67,7 @@ void ImageWidget::setImage(RawImage *image)
     m_image->destroy();
     m_image->setFormat(rawImageType.textureFormat);
     m_image->setSize(image->width(), image->height());
+    m_image->setMipLevels([&](){ int c = 0; int s = std::min(m_imgWidth, m_imgHeight); while(s>>=1)c++; return c; }());
     m_image->allocateStorage();
     m_image->setMinMagFilters(QOpenGLTexture::LinearMipMapLinear, QOpenGLTexture::Linear);
     m_image->setWrapMode(QOpenGLTexture::ClampToEdge);
@@ -105,28 +106,11 @@ void ImageWidget::blockRepaint(bool block)
     if(!block)update();
 }
 
-void ImageWidget::setLow(int low)
+void ImageWidget::setMTFParams(float low, float mid, float high)
 {
-    m_low = low/m_range;
+    m_low = low;
-    update();
+    m_mid = mid;
-}
+    m_high = high;
-
-void ImageWidget::setHigh(int high)
-{
-    m_high = high/m_range;
-    update();
-}
-
-void ImageWidget::setStrech(int stretch)
-{
-    m_stretch = stretch;
-    update();
-}
-
-void ImageWidget::setStretchParam(float param)
-{
-    qDebug() << param;
-    m_param = param;
     update();
 }
 
@@ -169,13 +153,10 @@ void ImageWidget::paintGL()
     if(height() > m_image->height()*m_scale)
         dy = -height()*0.5f + m_image->height()*m_scale*0.5f;
 
-    float s = 1.0f/(m_high-m_low);
     m_program->bind();
-    m_program->setUniformValue("scale", s, -m_low*s);
     m_program->setUniformValue("viewport", (float)width(), (float)height());
     m_program->setUniformValue("offset", dx, dy);
-    m_program->setUniformValue("stretch", m_stretch);
+    m_program->setUniformValue("mtf_param", m_low, m_mid, m_high);
-    m_program->setUniformValue("a", m_param);
     m_program->setUniformValue("zoom", 1.0f/m_scale);
     m_program->setUniformValue("bw", m_bwImg);
 

imagescrollareagl.h

@@ -33,12 +33,11 @@ class ImageWidget : public QOpenGLWidget
     int m_width, m_height;
     int m_imgWidth, m_imgHeight;
     float m_low;
+    float m_mid;
     float m_high;
-    int m_stretch;
     float m_range;
     float m_dx, m_dy;
     float m_scale;
-    float m_param;
     bool m_blockRepaint;
     bool m_bwImg;
 public:
@@ -49,10 +48,7 @@ public:
     void setScale(float scale);
     void blockRepaint(bool block);
 public slots:
-    void setLow(int low);
+    void setMTFParams(float low, float mid, float high);
-    void setHigh(int high);
-    void setStrech(int stretch);
-    void setStretchParam(float param);
     void setOffset(int dx, int dy);
     QImage renderToImage();
 protected:

mainwindow.cpp

@@ -43,10 +43,7 @@ MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
     setCentralWidget(m_imageGL);
 
     StretchPanel *stretchPanel = new  StretchPanel(this);
-    connect(stretchPanel, SIGNAL(lowChanged(int)), m_imageGL->imageWidget(), SLOT(setLow(int)));
+    connect(stretchPanel, SIGNAL(paramChanged(float,float,float)), m_imageGL->imageWidget(), SLOT(setMTFParams(float,float,float)));
-    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)));
 
     m_ringList = new ImageRingList(this);
     m_filesystem = new FilesystemWidget(m_ringList, this);

stfslider.cpp

@@ -3,9 +3,15 @@
 #include <QPainter>
 #include <QPaintEvent>
 
+static float clamp(float x)
+{
+    return std::min(std::max(x, 0.0f), 1.0f);
+}
+
 STFSlider::STFSlider(QWidget *parent) : QWidget(parent)
 {
     setMinimumHeight(15);
+    setMaximumHeight(15);
     setMouseTracking(true);
     m_blackPoint = 0;
     m_midPoint = 0.5;
@@ -13,6 +19,29 @@ STFSlider::STFSlider(QWidget *parent) : QWidget(parent)
     m_grabbed = -1;
 }
 
+float STFSlider::blackPoint() const
+{
+    return m_blackPoint;
+}
+
+float STFSlider::midPoint() const
+{
+    return m_midPoint;
+}
+
+float STFSlider::whitePoint() const
+{
+    return m_whitePoint;
+}
+
+void STFSlider::setMTFParams(float low, float mid, float high)
+{
+    m_blackPoint = clamp(low);
+    m_midPoint = clamp(mid);
+    m_whitePoint = clamp(high);
+    update();
+}
+
 void STFSlider::paintEvent(QPaintEvent *event)
 {
     QPainter painter(this);
@@ -77,7 +106,10 @@ void STFSlider::mouseMoveEvent(QMouseEvent *event)
         break;
     }
     if(m_grabbed >= 0)
-        repaint();
+    {
+        emit paramChanged(m_blackPoint, midPoint(), m_whitePoint);
+        update();
+    }
 }
 
 void STFSlider::mousePressEvent(QMouseEvent *event)
@@ -95,4 +127,5 @@ void STFSlider::mousePressEvent(QMouseEvent *event)
 void STFSlider::mouseReleaseEvent(QMouseEvent *)
 {
     m_grabbed = -1;
+    emit paramChanged(m_blackPoint, midPoint(), m_whitePoint);
 }

stfslider.h

@@ -13,6 +13,12 @@ class STFSlider : public QWidget
     int m_grabbed;
 public:
     explicit STFSlider(QWidget *parent = nullptr);
+    float blackPoint() const;
+    float midPoint() const;
+    float whitePoint() const;
+    void setMTFParams(float low, float mid, float high);
+signals:
+    void paramChanged(float blackPoint, float midPoint, float whitePoint);
 protected:
     void paintEvent(QPaintEvent *event) override;
     void mouseMoveEvent(QMouseEvent *event) override;

stretchpanel.cpp

@@ -1,42 +1,33 @@
 #include "stretchpanel.h"
 #include <QVBoxLayout>
 #include <QDebug>
+#include <QPushButton>
 #include "imageringlist.h"
-#include "stfslider.h"
+
+const float BLACK_POINT_SIGMA = -2.8f;
+const float MAD_TO_SIGMA = 1.4826f;
+const float TARGET_BACKGROUND = 0.25f;
+
+float MTF(float x, float m)
+{
+    if(x < 0)return 0;
+    if(x > 1)return 1;
+    return ((m - 1) * x) / ((2 * m - 1) * x - m);
+}
 
 StretchPanel::StretchPanel(QWidget *parent) : QWidget(parent)
 {
-    QVBoxLayout *layout = new QVBoxLayout(this);
+    QHBoxLayout *layout = new QHBoxLayout(this);
     setLayout(layout);
 
-    m_lowSlider = new QSlider(Qt::Horizontal, this);
+    m_stfSlider = new STFSlider(this);
-    m_highSlider = new QSlider(Qt::Horizontal, this);
+    layout->addWidget(m_stfSlider);
-    m_paramSlider = new QSlider(Qt::Horizontal, this);
+    connect(m_stfSlider, SIGNAL(paramChanged(float, float, float)), this, SIGNAL(paramChanged(float,float,float)));
 
-    STFSlider *stfslider = new STFSlider(this);
+    QPushButton *resetButton = new QPushButton(tr("Reset STF"), this);
-
+    resetButton->setSizePolicy(QSizePolicy::Maximum, QSizePolicy::Maximum);
-    m_lowSlider->setRange(0, UINT16_MAX);
+    layout->addWidget(resetButton);
-    m_lowSlider->setPageStep(512);
+    connect(resetButton, SIGNAL(pressed()), this, SLOT(resetMTF()));
-    m_highSlider->setRange(0, UINT16_MAX);
-    m_highSlider->setPageStep(512);
-    m_highSlider->setValue(UINT16_MAX);
-    m_paramSlider->setRange(0, UINT16_MAX);
-    m_paramSlider->setPageStep(512);
-
-    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(m_paramSlider);
-    layout->addWidget(m_stretchSelect);
-    layout->addWidget(stfslider);
-
-    connect(m_lowSlider, SIGNAL(valueChanged(int)), this, SIGNAL(lowChanged(int)));
-    connect(m_highSlider, SIGNAL(valueChanged(int)), this, SIGNAL(highChanged(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::imageLoaded(Image *img)
@@ -47,36 +38,19 @@ void StretchPanel::imageLoaded(Image *img)
         {
             double mean, stdDev, median;
             img->rawImage()->imageStats(&mean, &stdDev, &median, nullptr, nullptr);
-            double mad = img->rawImage()->MAD();
+            median /= 65536;
-            float l = median - mad;
+            double mad = img->rawImage()->MAD() / 65536;
-            m_lowSlider->setValue(l);
+            float bp = median + mad * BLACK_POINT_SIGMA * MAD_TO_SIGMA;
-            float p = std::log(0.25)/std::log(mean/UINT16_MAX);
+            float mid = MTF(median - bp, TARGET_BACKGROUND);
-            m_paramSlider->setValue(p * UINT16_MAX);
+            m_stfSlider->setMTFParams(bp, mid, 1.0f);
-            qDebug() << "Low" << l << p;
+            emit paramChanged(m_stfSlider->blackPoint(), m_stfSlider->midPoint(), 1.0f);
         }
     }
 }
 
-void StretchPanel::calculateParam()
+void StretchPanel::resetMTF()
 {
-    float val = m_paramSlider->value();
+    m_stfSlider->setMTFParams(0, 0.5, 1);
-    float param;
+    emit paramChanged(0, 0.5, 1);
-    switch(m_stretchSelect->currentIndex())
-    {
-    case 2:
-        param = val/UINT16_MAX;
-        param = 1.0f / (param * 5.0f + 1);
-        break;
-    case 3:
-        param = val;
-        break;
-    case 4:
-        param = 1.0f/std::max(0.00001f, 1.0f-(val/UINT16_MAX));
-        //val += 100;
-        //param = val/100.0f;
-        break;
-    default:
-        return;
-    }
-    emit paramChanged(param);
 }
+

stretchpanel.h

@@ -2,29 +2,21 @@
 #define STRETCHPANEL_H
 
 #include <QWidget>
-#include <QSlider>
+#include "stfslider.h"
-#include <QComboBox>
 
 class Image;
 
 class StretchPanel : public QWidget
 {
     Q_OBJECT
-    QSlider *m_lowSlider;
+    STFSlider *m_stfSlider;
-    QSlider *m_highSlider;
-    QSlider *m_paramSlider;
-    QComboBox *m_stretchSelect;
 public:
     explicit StretchPanel(QWidget *parent = nullptr);
 public slots:
     void imageLoaded(Image *img);
+    void resetMTF();
 signals:
-    void lowChanged(int low);
+    void paramChanged(float low, float mid, float high);
-    void highChanged(int high);
-    void stretchChanged(int stretch);
-    void paramChanged(float param);
-private slots:
-    void calculateParam();
 };
 
 #endif // STRETCHPANEL_H