Further cleanup to the image_viewer sample
Further cleanup to the image_viewer sample

xinhuang327/gxui,rnubel/gxui,MeGaPk/gxui,henrikhodne/gxui,Drahoslav7/gxui,abadojack/gxui,UIKit0/gxui,mzgnr/gxui,crr0004/gxui,treejames/gxui,leelib/gxui,google/gxui,insionng/gxui,pombredanne/gxui,CodyGuo/gxui,jmptrader/gxui,Anaminus/gxui,ylong/gxui,henrylee2cn/gxui,cainiaocome/gxui