Change Background Image for games (#2334)

* Added opacity change instead of blur for background image

* Fixed integer overflow when refreshing grid list

* Added slider to control background image opacity

* Added show background image button

* Added UI code for checkbox and English and Spanish translations for new UI elements

* Removed background image caching

* Background image update on apply/save

* Only recompute image if opacity or game changes

* Fixed segfault when trying to change opacity after table refresh

* Placed background image settings under GUI in settings file

src/qt_gui/translations/en.ts

@@ -757,6 +757,18 @@
 			<source>Disable Trophy Pop-ups</source>
 			<translation>Disable Trophy Pop-ups</translation>
 		</message>
+		<message>
+			<source>Background Image</source>
+			<translation>Background Image</translation>
+		</message>
+		<message>
+			<source>Show Background Image</source>
+			<translation>Show Background Image</translation>
+		</message>
+		<message>
+			<source>Opacity</source>
+			<translation>Opacity</translation>
+		</message>
 		<message>
 			<source>Play title music</source>
 			<translation>Play title music</translation>
@@ -853,6 +865,10 @@
 			<source>updaterGroupBox</source>
 			<translation>Update:\nRelease: Official versions released every month that may be very outdated, but are more reliable and tested.\nNightly: Development versions that have all the latest features and fixes, but may contain bugs and are less stable.</translation>
 		</message>
+		<message>
+			<source>GUIBackgroundImageGroupBox</source>
+			<translation>Background Image:\nControl the opacity of the game background image.</translation>
+		</message>
 		<message>
 			<source>GUIMusicGroupBox</source>
 			<translation>Play Title Music:\nIf a game supports it, enable playing special music when selecting the game in the GUI.</translation>

src/qt_gui/translations/es_ES.ts

@@ -748,6 +748,18 @@
 			<source>Disable Trophy Pop-ups</source>
 			<translation>Disable Trophy Pop-ups</translation>
 		</message>
+		<message>
+			<source>Background Image</source>
+			<translation>Imagen de fondo</translation>
+		</message>
+		<message>
+			<source>Show Background Image</source>
+			<translation>Mostrar Imagen de Fondo</translation>
+		</message>
+		<message>
+			<source>Opacity</source>
+			<translation>Opacidad</translation>
+		</message>
 		<message>
 			<source>Play title music</source>
 			<translation>Reproducir la música de apertura</translation>
@@ -844,6 +856,10 @@
 			<source>updaterGroupBox</source>
 			<translation>Actualización:\nRelease: Versiones oficiales lanzadas cada mes que pueden estar muy desactualizadas, pero son más confiables y están probadas.\nNightly: Versiones de desarrollo que tienen todas las últimas funciones y correcciones, pero pueden contener errores y son menos estables.</translation>
 		</message>
+		<message>
+			<source>GUIBackgroundImageGroupBox</source>
+			<translation>Imagen de fondo:\nControle la opacidad de la imagen de fondo del juego.</translation>
+		</message>
 		<message>
 			<source>GUIMusicGroupBox</source>
 			<translation>Reproducir Música del Título:\nSi un juego lo admite, habilita la reproducción de música especial al seleccionar el juego en la interfaz gráfica.</translation>