Method setAlpha

src/backend/common/image.hpp:39–39

        inline const std::shared_ptr<detail::image_impl>& impl() const { return mImage; }

        inline void setAlpha(const float pAlpha) { mImage->setAlpha(pAlpha); }

        inline void keepAspectRatio(const bool pKeep) { mImage->keepAspectRatio(pKeep); }