QQuickCanvasItem: optimize mimeToType

Provide early out, if mime is not image.
If mime is image, we can drop reduntant 'image/' prefix
from all strings.
Also we can pass type in lower register to QImage::save(),
so use only lower register in this function to de-duplicate
.rodata strings.

Change-Id: I6365edbe3c24ae096c5b1c23e8707299a8a5d5f3
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 16 insertions, 12 deletions

diff --git a/src/quick/items/context2d/qquickcanvasitem.cpp b/src/quick/items/context2d/qquickcanvasitem.cpp
index 368a2b78d1..dcad719ef0 100644
--- a/src/quick/items/context2d/qquickcanvasitem.cpp
+++ b/src/quick/items/context2d/qquickcanvasitem.cpp
@@ -1097,18 +1097,22 @@ QImage QQuickCanvasItem::toImage(const QRectF& rect) const
 
 static const char* mimeToType(const QString &mime)
 {
-    if (mime == QLatin1String("image/png"))
-        return "PNG";
-    else if (mime == QLatin1String("image/bmp"))
-        return "BMP";
-    else if (mime == QLatin1String("image/jpeg"))
-        return "JPEG";
-    else if (mime == QLatin1String("image/x-portable-pixmap"))
-        return "PPM";
-    else if (mime == QLatin1String("image/tiff"))
-        return "TIFF";
-    else if (mime == QLatin1String("image/xpm"))
-        return "XPM";
+    const QLatin1String imagePrefix("image/");
+    if (!mime.startsWith(imagePrefix))
+        return nullptr;
+    const QStringRef mimeExt = mime.midRef(imagePrefix.size());
+    if (mimeExt == QLatin1String("png"))
+        return "png";
+    else if (mimeExt == QLatin1String("bmp"))
+        return "bmp";
+    else if (mimeExt == QLatin1String("jpeg"))
+        return "jpeg";
+    else if (mimeExt == QLatin1String("x-portable-pixmap"))
+        return "ppm";
+    else if (mimeExt == QLatin1String("tiff"))
+        return "tiff";
+    else if (mimeExt == QLatin1String("xpm"))
+        return "xpm";
     return nullptr;
 }