Cache the image so we don't rebuild axes on image change.
Cache the image so we don't rebuild axes on image change.

ejeschke/ginga,Cadair/ginga,Cadair/ginga,naojsoft/ginga,rupak0577/ginga,pllim/ginga,ejeschke/ginga,ejeschke/ginga,pllim/ginga,Cadair/ginga,stscieisenhamer/ginga,stscieisenhamer/ginga,stscieisenhamer/ginga,rupak0577/ginga,rupak0577/ginga,naojsoft/ginga,pllim/ginga,naojsoft/ginga