Qt: HiDPI (retina) support for splash screen

- remove splash screen images (reduce binary size)
- dynamicly draw splash screen with available icon.
- remove testnet icon
- dynamicly colorize testnet icon

src/qt/networkstyle.cpp

@@ -11,22 +11,22 @@
 static const struct {
     const char *networkId;
     const char *appName;
-    const char *appIcon;
+    const int iconColorHueShift;
+    const int iconColorSaturationReduction;
     const char *titleAddText;
-    const char *splashImage;
 } network_styles[] = {
-    {"main", QAPP_APP_NAME_DEFAULT, ":/icons/bitcoin", "", ":/images/splash"},
-    {"test", QAPP_APP_NAME_TESTNET, ":/icons/bitcoin_testnet", QT_TRANSLATE_NOOP("SplashScreen", "[testnet]"), ":/images/splash_testnet"},
-    {"regtest", QAPP_APP_NAME_TESTNET, ":/icons/bitcoin_testnet", "[regtest]", ":/images/splash_testnet"}
+    {"main", QAPP_APP_NAME_DEFAULT, 0, 0, ""},
+    {"test", QAPP_APP_NAME_TESTNET, 70, 30, QT_TRANSLATE_NOOP("SplashScreen", "[testnet]")},
+    {"regtest", QAPP_APP_NAME_TESTNET, 70, 30, "[regtest]"}
 };
 static const unsigned network_styles_count = sizeof(network_styles)/sizeof(*network_styles);
 
 // titleAddText needs to be const char* for tr()
-NetworkStyle::NetworkStyle(const QString &appName, const QString &appIcon, const char *titleAddText, const QString &splashImage):
+NetworkStyle::NetworkStyle(const QString &appName, const int iconColorHueShift, const int iconColorSaturationReduction, const char *titleAddText):
     appName(appName),
-    appIcon(appIcon),
-    titleAddText(qApp->translate("SplashScreen", titleAddText)),
-    splashImage(splashImage)
+    iconColorHueShift(iconColorHueShift),
+    iconColorSaturationReduction(iconColorSaturationReduction),
+    titleAddText(qApp->translate("SplashScreen", titleAddText))
 {
 }
 
@@ -38,10 +38,78 @@ const NetworkStyle *NetworkStyle::instantiate(const QString &networkId)
         {
             return new NetworkStyle(
                     network_styles[x].appName,
-                    network_styles[x].appIcon,
-                    network_styles[x].titleAddText,
-                    network_styles[x].splashImage);
+                    network_styles[x].iconColorHueShift,
+                    network_styles[x].iconColorSaturationReduction,
+                    network_styles[x].titleAddText);
         }
     }
     return 0;
 }
+
+QIcon NetworkStyle::getAppIcon() const
+{
+    return getAppIcon(QSize(256,256));
+}
+
+QIcon NetworkStyle::getAppIcon(const QSize size) const
+{
+    // load pixmap
+    QPixmap pixmap(":/icons/bitcoin");
+
+    if(pixmap.size().width() != size.width() && pixmap.size().height() != size.height())
+    {
+        QPixmap scaledPixmap = pixmap.scaled(size, Qt::KeepAspectRatio);
+        if(!scaledPixmap.isNull())
+        {
+            pixmap = scaledPixmap;
+        }
+    }
+
+    if(iconColorHueShift != 0 && iconColorSaturationReduction != 0)
+    {
+        // copy the pixmap because on linux the original pixmap will be affected
+        pixmap = pixmap.copy();
+
+        // generate QImage from QPixmap
+        QImage img = pixmap.toImage();
+
+        int h,s,l,a;
+
+        // traverse though lines
+        for(int y=0;y<img.height();y++)
+        {
+            QRgb *scL = reinterpret_cast< QRgb *>( img.scanLine( y ) );
+
+            // loop through pixels
+            for(int x=0;x<img.width();x++)
+            {
+                // preserve alpha because QColor::getHsl doesen't return the alpha value
+                a = qAlpha(scL[x]);
+                QColor col(scL[x]);
+
+                // get hue value
+                col.getHsl(&h,&s,&l);
+
+                // rotate color on RGB color circle
+                // 70° should end up with the typical "testnet" green
+                h+=iconColorHueShift;
+
+                // change saturation value
+                if(s>iconColorSaturationReduction)
+                {
+                    s -= iconColorSaturationReduction;
+                }
+                col.setHsl(h,s,l,a);
+
+                // set the pixel
+                scL[x] = col.rgba();
+            }
+        }
+
+        //convert back to QPixmap
+        pixmap.convertFromImage(img);
+    }
+
+    QIcon icon(pixmap);
+    return icon;
+}