Android photo gallery

I need a customizeable photo gallery app for Android. The special features needed are: 1- be able to specify which folders to display on the main screen, 2- set each folder's thumbnail to the first picture in that folder. 3- Search by tags IPTC => Keywords and/or XMP-dc => Subject 4- Star or favorite photos, then be able to see all the favorites on one screen. That screen would allow unfavoriting single or all pictures. My goal is to put just the photos I want into 10-15 folder which would be put on an SD card or into a local folder, point the gallery at that location, and on the Gallery homepage would be thumbnails for each folder as well as the name of the folder. These should fit on one screen and basically fill the screen. On the main screen there should be buttons to open the settings, view the favorites and a search bar. When opening the folders, the thumbnails for the pics inside should open fairly large on a new screen and scroll side to side (up and down would work too in case it causes problems for some reason). On a 10" tablet, there should probably only be 4 thumbs across and 2 high. Making the thumbsize user adjustable would be ideal, but not necessary if it is going to add significantly to the cost. Photos should be sorted alphabetically by default. When opening a photo, it should open full screen (or as close as possible while maintaining the aspect ratio). There should be a button to add to favorites (an open star is fine). I would prefer a back button be visible at all times, but we can discuss the best way to handle this. Keeping a tool bar with a back button, home button and searchbar visible on every page might be best, but I don't want to make it too busy. On the favorites page, there should be an option to unfavorite selected picture or all. An option to email favorites would also be ideal. Please let me know if you have any questions. This would need to be a fairly quick turnaround, so the favorites feature could be left for later if that is difficult. Otherwise the look should be minimalist, black background and work smoothly and quickly.