var preLoad = {
'imgHomeOff' : "/App_Themes/HyperVizeTheme/img/HomeOff.gif",
'imgHomeOffRoll' : "/App_Themes/HyperVizeTheme/img/HomeOffRoll.gif",
'imgHomeSelected' : "/App_Themes/HyperVizeTheme/img/HomeSelected.gif",
'imgHomeSelectedRoll' : "/App_Themes/HyperVizeTheme/img/HomeSelectedRoll.gif",

'imgServiceOff' : "/App_Themes/HyperVizeTheme/img/ServicesOff.gif",
'imgServiceOffRoll' : "/App_Themes/HyperVizeTheme/img/ServicesOffRoll.gif",
'imgServiceSelected' : "/App_Themes/HyperVizeTheme/img/ServicesSelected.gif",
'imgServiceSelectedRoll' : "/App_Themes/HyperVizeTheme/img/ServicesSelectedRoll.gif",

'imgTechOff' : "/App_Themes/HyperVizeTheme/img/TechOff.gif",
'imgTechOffRoll' : "/App_Themes/HyperVizeTheme/img/TechOffRoll.gif",
'imgTechSelected' : "/App_Themes/HyperVizeTheme/img/TechSelected.gif",
'imgTechSelectedRoll' : "/App_Themes/HyperVizeTheme/img/TechSelectedRoll.gif",

'imgIndustryOff' : "/App_Themes/HyperVizeTheme/img/IndustryOff.gif",
'imgIndustryOffRoll' : "/App_Themes/HyperVizeTheme/img/IndustryOffRoll.gif",
'imgIndustrySelected' : "/App_Themes/HyperVizeTheme/img/IndustrySelected.gif",
'imgIndustrySelectedRoll' : "/App_Themes/HyperVizeTheme/img/IndustrySelectedRoll.gif"
}; 
var loadedImages = {};

for (var name in preLoad) {
    loadedImages[name] = new Image();
    loadedImages[name].src = preLoad[name];
}

function swapImage(img, imgName) {
    img.src = loadedImages[imgName].src;
}
function restoreImage(img, imgName) {
    img.src = loadedImages[imgName].src;
}