//Define the current window
var myWin = Titanium.UI.currentWindow;
 
//Define the button to activate camera
var openGalleryBtn = Ti.UI.createButton({
   title   : 'Open Gallery',
   top    : 10      //Set the button position on the screen
});
 
openGalleryBtn.addEventListener('click', function(){
 
    //To open gallery
   Titanium.Media.openPhotoGallery({
success : function(event) {
              
              //Holds the captured image
          var selectedImg= event.media;
 
               // Condition to check the selected media
              if(event.mediaType == Ti.Media.MEDIA_TYPE_PHOTO) {
 
//Define an image view with selected image from gallery
                   var imgView = Titanium.UI.createImageView({
   left       : 10,
                                   width    : 250,
   height   : 250,
   image   :  selectedImg    //Set selected image from gallery
});
 
//Add the image to window for displaying
myWin.add(imgView);
}
},
cancel : function() {
//While cancellation of the process
},
error : function(error) {
               // If any error occurs during the process
 
}
});
 
THAT'S IT