Merge lp:~johbjo/qpdfview/invertlight into lp:qpdfview

[Johan]

Changed named to "Invert lightness" and fixed tab indentations. There seems to exist various definition of "lightness" related to various colour spaces, but this transformation probably inverts it either way.

Here is the comment I wrote about how this works:

"This is a transformation in RGB space that mirrors the color coordinates about the plane that intersects the mid point of the cube (0.5, 0.5, 0.5) and is perpendicular to the diagonal vector (1,1,1).

"Each color-coordinate is moved along the (1,1,1)-vector twice its distance from this mid plane.

"Moving a color-coordinate along (1,1,1) preserves the "hue" but changes the "lightness" of the color."

The absolute differences between the components are preserved, which means the "hue" is preserved.

Here are the calculations:

The mid plane is: r + g + b = 1.5

To find the distance t for a given point (r,g,b), we can plug in: r+t + g+t + b+t = 1.5 => t = (1.5 - r - g - b) / 3

The mirrored point is then (r+2*t, g+2*t, b+2*t). When the range is 0-255, we have 1.5*255 = 382.5.

I simplified to: d = (382.5 - r - g - b) / 1.5

[Adam Reichold (adamreichold)]

Hello Johan,

thank you very much for your contribution!

I have to admit that I do not yet fully understand how this works. I am therefore also slightly uncomfortable with the name.

Is the idea to transform RGB into HSL and there invert the lightness component but keep hue and saturation intact? If so, wouldn't maybe "Invert lightness" be a more precise name?

Best regards,
Adam

[Adam Reichold (adamreichold)]

Hello again,

this looks good to me now. Thank you for taking the time to explain things.

One more thing I wonder is whether this should be locked against "Invert colors" so that one can either invert colors or lightness, but not both? Technically, chaining the transformations is not a problem, but I am not sure if the result is useful.

Best regards,
Adam

review: Approve

[Adam Reichold (adamreichold)]

Note that I had to change the keyboard shortcut as Ctrl+L is already used to focus the scale factor. I chose Ctrl+Shift+I instead which somewhat meshes with the other render flags modifiers...

=== modified file 'sources/documentview.cpp'
--- sources/documentview.cpp	2020-12-15 20:53:35 +0000
+++ sources/documentview.cpp	2020-12-26 16:15:31 +0000
@@ -814,6 +814,11 @@
         m_renderFlags |= InvertColors;
     }
 
+    if(s_settings->documentView().invertLightness())
+    {
+        m_renderFlags |= InvertLightness;
+    }
+    
     if(s_settings->documentView().convertToGrayscale())
     {
         m_renderFlags |= ConvertToGrayscale;
@@ -1137,6 +1142,15 @@
             s_settings->documentView().setInvertColors(invertColors());
         }
 
+        if(changedFlags.testFlag(InvertLightness))
+        {
+            prepareBackground();
+
+            emit invertLightnessChanged(invertLightness());
+
+            s_settings->documentView().setInvertLightness(invertLightness());
+        }
+
         if(changedFlags.testFlag(ConvertToGrayscale))
         {
             emit convertToGrayscaleChanged(convertToGrayscale());
@@ -2827,7 +2841,7 @@
     {
         backgroundColor = s_settings->pageItem().paperColor();
 
-        if(invertColors())
+        if(invertColors() || invertLightness())
         {
             backgroundColor.setRgb(~backgroundColor.rgb());
         }

=== modified file 'sources/documentview.h'
--- sources/documentview.h	2018-03-28 19:19:40 +0000
+++ sources/documentview.h	2020-12-26 16:15:31 +0000
@@ -112,6 +112,9 @@
     bool invertColors() const { return m_renderFlags.testFlag(InvertColors); }
     void setInvertColors(bool invertColors) { setRenderFlag(InvertColors, invertColors); }
 
+    bool invertLightness() const { return m_renderFlags.testFlag(InvertLightness); }
+    void setInvertLightness(bool invertLightness) { setRenderFlag(InvertLightness, invertLightness); }
+
     bool convertToGrayscale() const { return m_renderFlags.testFlag(ConvertToGrayscale); }
     void setConvertToGrayscale(bool convertToGrayscale) { setRenderFlag(ConvertToGrayscale, convertToGrayscale); }
 
@@ -193,6 +196,7 @@
     void renderFlagsChanged(qpdfview::RenderFlags renderFlags);
 
     void invertColorsChanged(bool invertColors);
+    void invertLightnessChanged(bool invertLightness);
     void convertToGrayscaleChanged(bool convertToGrayscale);
     void trimMarginsChanged(bool trimMargins);
 

=== modified file 'sources/mainwindow.cpp'
--- sources/mainwindow.cpp	2020-01-03 18:40:18 +0000
+++ sources/mainwindow.cpp	2020-12-26 16:15:31 +0000
@@ -626,6 +626,7 @@
     m_rotateRightAction->setEnabled(hasCurrent);
 
     m_invertColorsAction->setEnabled(hasCurrent);
+    m_invertLightnessAction->setEnabled(hasCurrent);
     m_convertToGrayscaleAction->setEnabled(hasCurrent);
     m_trimMarginsAction->setEnabled(hasCurrent);
 
@@ -706,6 +707,7 @@
         on_currentTab_scaleFactorChanged(tab->scaleFactor());
 
         on_currentTab_invertColorsChanged(tab->invertColors());
+        on_currentTab_invertLightnessChanged(tab->invertLightness());
         on_currentTab_convertToGrayscaleChanged(tab->convertToGrayscale());
         on_currentTab_trimMarginsChanged(tab->trimMargins());
 
@@ -755,6 +757,7 @@
         m_fitToPageWidthModeAction->setChecked(false);
 
         m_invertColorsAction->setChecked(false);
+        m_invertLightnessAction->setChecked(false);
         m_convertToGrayscaleAction->setChecked(false);
         m_trimMarginsAction->setChecked(false);
 
@@ -1086,6 +1089,13 @@
     m_invertColorsAction->setChecked(invertColors);
 }
 
+void MainWindow::on_currentTab_invertLightnessChanged(bool invertLightness)
+{
+    ONLY_IF_SENDER_IS_CURRENT_TAB
+
+    m_invertLightnessAction->setChecked(invertLightness);
+}
+
 void MainWindow::on_currentTab_convertToGrayscaleChanged(bool convertToGrayscale)
 {
     ONLY_IF_SENDER_IS_CURRENT_TAB
@@ -1770,6 +1780,11 @@
     currentTab()->setInvertColors(checked);
 }
 
+void MainWindow::on_invertLightness_triggered(bool checked)
+{
+    currentTab()->setInvertLightness(checked);
+}
+
 void MainWindow::on_convertToGrayscale_triggered(bool checked)
 {
     currentTab()->setConvertToGrayscale(checked);
@@ -2783,6 +2798,7 @@
     connect(tab, SIGNAL(renderFlagsChanged(qpdfview::RenderFlags)), SLOT(on_currentTab_renderFlagsChanged(qpdfview::RenderFlags)));
 
     connect(tab, SIGNAL(invertColorsChanged(bool)), SLOT(on_currentTab_invertColorsChanged(bool)));
+    connect(tab, SIGNAL(invertLightnessChanged(bool)), SLOT(on_currentTab_invertLightnessChanged(bool)));
     connect(tab, SIGNAL(convertToGrayscaleChanged(bool)), SLOT(on_currentTab_convertToGrayscaleChanged(bool)));
     connect(tab, SIGNAL(trimMarginsChanged(bool)), SLOT(on_currentTab_trimMarginsChanged(bool)));
 
@@ -3213,6 +3229,7 @@
     m_rotateRightAction = createAction(tr("Rotate &right"), QLatin1String("rotateRight"), QLatin1String("object-rotate-right"), ShortcutHandler::defaultRotateRight(), SLOT(on_rotateRight_triggered()));
 
     m_invertColorsAction = createAction(tr("Invert colors"), QLatin1String("invertColors"), QIcon(), QKeySequence(Qt::CTRL + Qt::Key_I), SLOT(on_invertColors_triggered(bool)), true);
+    m_invertLightnessAction = createAction(tr("Invert lightness"), QLatin1String("invertLightness"), QIcon(), QKeySequence(Qt::CTRL + Qt::Key_L), SLOT(on_invertLightness_triggered(bool)), true);
     m_convertToGrayscaleAction = createAction(tr("Convert to grayscale"), QLatin1String("convertToGrayscale"), QIcon(), QKeySequence(Qt::CTRL + Qt::Key_U), SLOT(on_convertToGrayscale_triggered(bool)), true);
     m_trimMarginsAction = createAction(tr("Trim margins"), QLatin1String("trimMargins"), QIcon(), QKeySequence(Qt::CTRL + Qt::SHIFT + Qt::Key_U), SLOT(on_trimMargins_triggered(bool)), true);
 
@@ -3530,7 +3547,7 @@
     m_viewMenu->addSeparator();
     m_viewMenu->addActions(QList< QAction* >() << m_rotateLeftAction << m_rotateRightAction);
     m_viewMenu->addSeparator();
-    m_viewMenu->addActions(QList< QAction* >() << m_invertColorsAction << m_convertToGrayscaleAction << m_trimMarginsAction);
+    m_viewMenu->addActions(QList< QAction* >() << m_invertColorsAction << m_invertLightnessAction << m_convertToGrayscaleAction << m_trimMarginsAction);
 
     m_compositionModeMenu = m_viewMenu->addMenu(tr("Composition"));
     m_compositionModeMenu->addAction(m_darkenWithPaperColorAction);
@@ -3789,6 +3806,13 @@
     mainWindow()->on_invertColors_triggered(checked);
 }
 
+void MainWindowAdaptor::invertLightness(bool checked)
+{
+    ONLY_IF_CURRENT_TAB
+
+    mainWindow()->on_invertLightness_triggered(checked);
+}
+
 void MainWindowAdaptor::convertToGrayscale(bool checked)
 {
     ONLY_IF_CURRENT_TAB

=== modified file 'sources/mainwindow.h'
--- sources/mainwindow.h	2018-03-29 18:56:40 +0000
+++ sources/mainwindow.h	2020-12-26 16:15:31 +0000
@@ -121,6 +121,7 @@
     void on_currentTab_renderFlagsChanged(qpdfview::RenderFlags renderFlags);
 
     void on_currentTab_invertColorsChanged(bool invertColors);
+    void on_currentTab_invertLightnessChanged(bool invertLightness);
     void on_currentTab_convertToGrayscaleChanged(bool convertToGrayscale);
     void on_currentTab_trimMarginsChanged(bool trimMargins);
 
@@ -206,6 +207,7 @@
     void on_rotateRight_triggered();
 
     void on_invertColors_triggered(bool checked);
+    void on_invertLightness_triggered(bool checked);
     void on_convertToGrayscale_triggered(bool checked);
     void on_trimMargins_triggered(bool checked);
     void on_darkenWithPaperColor_triggered(bool checked);
@@ -405,6 +407,7 @@
     QAction* m_rotateRightAction;
 
     QAction* m_invertColorsAction;
+    QAction* m_invertLightnessAction;
     QAction* m_convertToGrayscaleAction;
     QAction* m_trimMarginsAction;
     QAction* m_darkenWithPaperColorAction;
@@ -560,6 +563,7 @@
     Q_NOREPLY void fitToPageSizeMode(bool checked);
 
     Q_NOREPLY void invertColors(bool checked);
+    Q_NOREPLY void invertLightness(bool checked);
     Q_NOREPLY void convertToGrayscale(bool checked);
     Q_NOREPLY void trimMargins(bool checked);
 

=== modified file 'sources/pageitem.cpp'
--- sources/pageitem.cpp	2020-01-01 08:54:36 +0000
+++ sources/pageitem.cpp	2020-12-26 16:15:31 +0000
@@ -1182,6 +1182,11 @@
 
         QColor paperColor = s_settings->pageItem().paperColor();
 
+        if(m_renderParam.invertLightness())
+        {
+            paperColor.setRgb(~paperColor.rgb());
+        }
+
         if(m_renderParam.invertColors())
         {
             paperColor.setRgb(~paperColor.rgb());

=== modified file 'sources/presentationview.cpp'
--- sources/presentationview.cpp	2019-05-12 09:55:28 +0000
+++ sources/presentationview.cpp	2020-12-26 16:15:31 +0000
@@ -172,7 +172,7 @@
         prepareScene();
         prepareView();
 
-        if(changedFlags.testFlag(InvertColors))
+        if(changedFlags.testFlag(InvertColors) || changedFlags.testFlag(InvertLightness))
         {
             prepareBackground();
         }
@@ -568,6 +568,11 @@
         backgroundColor.setRgb(~backgroundColor.rgb());
     }
 
+    if(m_renderFlags.testFlag(InvertLightness))
+    {
+        backgroundColor.setRgb(~backgroundColor.rgb());
+    }
+    
     scene()->setBackgroundBrush(QBrush(backgroundColor));
 }
 

=== modified file 'sources/renderparam.h'
--- sources/renderparam.h	2015-05-25 09:30:55 +0000
+++ sources/renderparam.h	2020-12-26 16:15:31 +0000
@@ -35,7 +35,8 @@
     ConvertToGrayscale = 1 << 1,
     TrimMargins = 1 << 2,
     DarkenWithPaperColor = 1 << 3,
-    LightenWithPaperColor = 1 << 4
+    LightenWithPaperColor = 1 << 4,
+    InvertLightness = 1 << 5
 };
 
 Q_DECLARE_FLAGS(RenderFlags, RenderFlag)
@@ -89,6 +90,9 @@
     bool invertColors() const { return d->flags.testFlag(InvertColors); }
     void setInvertColors(bool invertColors) { setFlag(InvertColors, invertColors); }
 
+    bool invertLightness() const { return d->flags.testFlag(InvertLightness); }
+    void setInvertLightness(bool invertLightness) { setFlag(InvertLightness, invertLightness); }
+
     bool convertToGrayscale() const { return d->flags.testFlag(ConvertToGrayscale); }
     void setConvertToGrayscale(bool convertToGrayscale) { setFlag(ConvertToGrayscale, convertToGrayscale); }
 

=== modified file 'sources/rendertask.cpp'
--- sources/rendertask.cpp	2016-11-26 20:18:57 +0000
+++ sources/rendertask.cpp	2020-12-26 16:15:31 +0000
@@ -21,6 +21,7 @@
 
 #include "rendertask.h"
 
+#include <cmath>
 #include <QApplication>
 #include <qmath.h>
 #include <QPainter>
@@ -155,6 +156,38 @@
                   static_cast< qreal >(bottom - top) / height);
 }
 
+void invertLightness(QImage& image)
+{
+    QRgb* const begin = reinterpret_cast< QRgb* >(image.bits());
+    QRgb* const end = reinterpret_cast< QRgb* >(image.bits() + image.byteCount());
+
+    // This is a transformation in RGB space that mirrors the color coordinates
+    // about the plane that intersects the mid point of the cube (0.5, 0.5, 0.5)
+    // and is perpendicular to the diagonal vector (1,1,1).
+    //
+    // Each color-coordinate is moved along the (1,1,1)-vector twice its
+    // distance from this mid plane.
+    //
+    // Moving a color-coordinate along (1,1,1) preserves the "hue" 
+    // but changes the "lightness" of the color.
+    
+    for(QRgb* pointer = begin; pointer != end; ++pointer)
+    {
+        const int alpha = qAlpha(*pointer);
+        int r = qRed(*pointer);
+        int g = qGreen(*pointer);
+        int b = qBlue(*pointer);
+        int d = (int) round((382.5 - r - g - b) / 1.5);
+        r = r + d;
+        g = g + d;
+        b = b + d;
+        r = qBound(0, r, 255);
+        g = qBound(0, g, 255);
+        b = qBound(0, b, 255);
+        *pointer = qRgba(r, g, b, alpha);
+    }
+}
+
 void convertToGrayscale(QImage& image)
 {
     QRgb* const begin = reinterpret_cast< QRgb* >(image.bits());
@@ -482,6 +515,13 @@
         convertToGrayscale(image);
     }
 
+    if(m_renderParam.invertLightness())
+    {
+        CANCELLATION_POINT
+
+        invertLightness(image);
+    }
+
     if(m_renderParam.invertColors())
     {
         CANCELLATION_POINT

=== modified file 'sources/settings.cpp'
--- sources/settings.cpp	2020-12-15 20:53:35 +0000
+++ sources/settings.cpp	2020-12-26 16:15:31 +0000
@@ -627,6 +627,16 @@
     m_settings->setValue("documentView/invertColors", invertColors);
 }
 
+bool Settings::DocumentView::invertLightness() const
+{
+    return m_settings->value("documentView/invertLightness", Defaults::DocumentView::invertLightness()).toBool();
+}
+
+void Settings::DocumentView::setInvertLightness(bool invertLightness)
+{
+    m_settings->setValue("documentView/invertLightness", invertLightness);
+}
+
 bool Settings::DocumentView::convertToGrayscale() const
 {
     return m_settings->value("documentView/convertToGrayscale", Defaults::DocumentView::convertToGrayscale()).toBool();

=== modified file 'sources/settings.h'
--- sources/settings.h	2020-12-15 20:53:35 +0000
+++ sources/settings.h	2020-12-26 16:15:31 +0000
@@ -262,6 +262,9 @@
         bool invertColors() const;
         void setInvertColors(bool invertColors);
 
+        bool invertLightness() const;
+        void setInvertLightness(bool invertLightness);
+
         bool convertToGrayscale() const;
         void setConvertToGrayscale(bool convertToGrayscale);
 
@@ -606,6 +609,7 @@
         static Rotation rotation() { return RotateBy0; }
 
         static bool invertColors() { return false; }
+        static bool invertLightness() { return false; }
         static bool convertToGrayscale() { return false; }
         static bool trimMargins() { return false; }