How to export image metadata? I'd like to factory reset my Lollipop smartphone. But I have many pictures, downloaded from the web, shared by friends or taken with the stock camera, which I have tagged with my contact names, added google map geolocation, categories. I've done all of that within the native Android gallery app.

If I copy such images to another folder, the copy does not show the infos I previously added. It is the same if I make a copy on my laptop. So, is there any app to export those metadata, which are not supposedly included in the image file?

thanks.
Take a look at Titanium Backup, it will backup all the data saved in the Contacts app and Gallery app and you can either transfer it to a new phone, or extract the sql-lite db's contained in the backup and (hopefully) get your data into a spreadsheet or something. (as mentioned here)

An alternative method (without root) is to use the adb backup command. Since you're restoring your phone you might want to just adb backup -all -apk -system -shared and that will get everything. For just the data you want you can instead use -all -noapk -system -shared and it will be faster, but no apks. You can easily unzip the backup and locate your /data/Gallery.apk or Contacts.apk and unzip those to find a sql-lite database (or many). You can either extract the database or transfer the whole /data/Gallery.apk to your restored device.

Hope this helps