[qtdeclarative] Load images in an OpenGL texture friendly format. Con…

…tributes to JB#49193

Pre-emptively convert images in the pixmap cache to RGBX8888 or
RGBA8888_Premultipled to avoid potentially doing the conversion in the
render thread where it will directly impact the frame rate.

src/quick/util/qquickpixmapcache.cpp

@@ -347,26 +347,30 @@ QNetworkAccessManager *QQuickPixmapReader::networkAccessManager()
     return accessManager;
 }
 
-static void maybeRemoveAlpha(QImage *image)
-{
-    // If the image
-    if (image->hasAlphaChannel() && image->data_ptr()
-            && !image->data_ptr()->checkForAlphaPixels()) {
-        switch (image->format()) {
-        case QImage::Format_RGBA8888:
-        case QImage::Format_RGBA8888_Premultiplied:
-            *image = image->convertToFormat(QImage::Format_RGBX8888);
-            break;
-        case QImage::Format_A2BGR30_Premultiplied:
-            *image = image->convertToFormat(QImage::Format_BGR30);
-            break;
-        case QImage::Format_A2RGB30_Premultiplied:
-            *image = image->convertToFormat(QImage::Format_RGB30);
-            break;
-        default:
-            *image = image->convertToFormat(QImage::Format_RGB32);
-            break;
-        }
+namespace {
+
+class ConversionImage : public QImage
+{
+public:
+    using QImage::convertToFormat_inplace;
+};
+
+}
+
+static void convertImageToFormat(QImage *image, QImage::Format format)
+{
+    if (!static_cast<ConversionImage *>(image)->convertToFormat_inplace(format, Qt::AutoColor)) {
+        *image = image->convertToFormat(format);
+    }
+}
+
+static void optimizeImageForTexture(QImage *image)
+{
+    if (!image->hasAlphaChannel()
+            || (image->data_ptr() && !image->data_ptr()->checkForAlphaPixels())) {
+        convertImageToFormat(image, QImage::Format_RGBX8888);
+    } else {
+        convertImageToFormat(image, QImage::Format_RGBA8888_Premultiplied);
     }
 }
 
@@ -403,7 +407,7 @@ static bool readImage(const QUrl& url, QIODevice *dev, QImage *image, QString *e
         *impsize = imgio.size();
 
     if (imgio.read(image)) {
-        maybeRemoveAlpha(image);
+        optimizeImageForTexture(image);
         if (impsize && impsize->width() < 0)
             *impsize = image->size();
         return true;