diff -Naur kdiff3-1.8.2/src/directorymergewindow.cpp kdiff3/src/directorymergewindow.cpp
--- kdiff3-1.8.2/src/directorymergewindow.cpp	2020-03-28 00:08:41.000000000 +0300
+++ kdiff3/src/directorymergewindow.cpp	2020-05-16 23:51:28.628819480 +0300
@@ -584,7 +584,10 @@
             //QPixmap icon = value.value<QPixmap>(); //pixmap(column);
             if(!icon.isNull())
             {
-                int yOffset = (sizeHint(option, index).height() - icon.height()) / 2;
+                const auto dpr = thePainter->device()->devicePixelRatioF();
+                const int w = qRound(icon.width() / dpr);
+                const int h = qRound(icon.height() / dpr);
+                int yOffset = (sizeHint(option, index).height() - h) / 2;
                 thePainter->drawPixmap(x + 2, y + yOffset, icon);
 
                 int i = index == d->m_selection1Index ? 1 : index == d->m_selection2Index ? 2 : index == d->m_selection3Index ? 3 : 0;
@@ -593,20 +596,20 @@
                     Options* pOpts = d->m_pOptions;
                     QColor c(i == 1 ? pOpts->m_colorA : i == 2 ? pOpts->m_colorB : pOpts->m_colorC);
                     thePainter->setPen(c); // highlight() );
-                    thePainter->drawRect(x + 2, y + yOffset, icon.width(), icon.height());
+                    thePainter->drawRect(x + 2, y + yOffset, w, h);
                     thePainter->setPen(QPen(c, 0, Qt::DotLine));
-                    thePainter->drawRect(x + 1, y + yOffset - 1, icon.width() + 2, icon.height() + 2);
+                    thePainter->drawRect(x + 1, y + yOffset - 1, w + 2, h + 2);
                     thePainter->setPen(Qt::white);
                     QString s(QChar('A' + i - 1));
 
-                    thePainter->drawText(x + 2 + (icon.width() - Utils::getHorizontalAdvance(thePainter->fontMetrics(), s)) / 2,
-                                y + yOffset + (icon.height() + thePainter->fontMetrics().ascent()) / 2 - 1,
+                    thePainter->drawText(x + 2 + (w - Utils::getHorizontalAdvance(thePainter->fontMetrics(), s)) / 2,
+                                y + yOffset + (h + thePainter->fontMetrics().ascent()) / 2 - 1,
                                 s);
                 }
                 else
                 {
                     thePainter->setPen(m_pDMW->palette().window().color());
-                    thePainter->drawRect(x + 1, y + yOffset - 1, icon.width() + 2, icon.height() + 2);
+                    thePainter->drawRect(x + 1, y + yOffset - 1, w + 2, h + 2);
                 }
                 return;
             }
diff -Naur kdiff3-1.8.2/src/main.cpp kdiff3/src/main.cpp
--- kdiff3-1.8.2/src/main.cpp	2020-03-28 00:08:41.000000000 +0300
+++ kdiff3/src/main.cpp	2020-05-16 23:54:52.115359858 +0300
@@ -80,6 +80,7 @@
 {
     const QLatin1String appName("kdiff3");
 
+    QCoreApplication::setAttribute(Qt::AA_UseHighDpiPixmaps);
     QApplication app(argc, argv); // KAboutData and QCommandLineParser depend on this being setup.
     KLocalizedString::setApplicationDomain(appName.data());
 
diff -Naur kdiff3-1.8.2/src/mergeresultwindow.cpp kdiff3/src/mergeresultwindow.cpp
--- kdiff3-1.8.2/src/mergeresultwindow.cpp	2020-03-28 00:08:41.000000000 +0300
+++ kdiff3/src/mergeresultwindow.cpp	2020-05-16 23:58:03.903812330 +0300
@@ -1970,8 +1970,11 @@
     if(!m_bCursorUpdate) // Don't redraw everything for blinking cursor?
     {
         m_selection.bSelectionContainsData = false;
-        if(size() != m_pixmap.size())
-            m_pixmap = QPixmap(size());
+        const auto dpr = devicePixelRatioF();
+        if(size() * dpr != m_pixmap.size()){
+            m_pixmap = QPixmap(size() * dpr);
+            m_pixmap.setDevicePixelRatio(devicePixelRatioF());
+        }
 
         RLPainter p(&m_pixmap, m_pOptions->m_bRightToLeftLanguage, width(), fontWidth);
         p.setFont(font());
diff -Naur kdiff3-1.8.2/src/Overview.cpp kdiff3/src/Overview.cpp
--- kdiff3-1.8.2/src/Overview.cpp	2020-03-28 00:08:41.000000000 +0300
+++ kdiff3/src/Overview.cpp	2020-05-16 23:39:48.102500085 +0300
@@ -271,7 +271,8 @@
     int h = height() - 1;
     int w = width();
 
-    if(m_pixmap.size() != size())
+    const auto dpr = devicePixelRatioF();
+    if(m_pixmap.size() != size() * dpr)
     {
         if(m_pOptions->m_bWordWrap)
         {
@@ -287,7 +288,8 @@
             m_nofLines = m_pDiff3LineList->size();
         }
 
-        m_pixmap = QPixmap(size());
+        m_pixmap = QPixmap(size() * dpr);
+        m_pixmap.setDevicePixelRatio(dpr);
 
         QPainter p(&m_pixmap);
         p.fillRect(rect(), m_pOptions->m_bgColor);