Question: I have a button with image.How can I localize it, in order it to have another image on different language ?

Answer: 
If your image is not in an xcassets you can localize it in the file inspector. 
If you image is in an xcassets, you can include the language identifier in its name, or as @jdapps said, localize the image name in a strings file.
Select the “image” in the project navigator. Next, bring up the file inspector, and locate the localization section, in which you’ll see a button named “*Localize…*”. Click the button and you’ll be prompted for confirmation. Choose English and click the “Localize” button to confirm.

[![enter image description here](https://i.stack.imgur.com/xaFy4.png)](https://i.stack.imgur.com/xaFy4.png)

[![enter image description here](https://i.stack.imgur.com/U8RGi.png)](https://i.stack.imgur.com/U8RGi.png)

[![enter image description here](https://i.stack.imgur.com/rsSNF.png)](https://i.stack.imgur.com/rsSNF.png)

Switch back to the finder and local the project directory. You’ll find two folders: `en.lproj` and `Base.lproj`. Both folders are automatically generated by Xcode for localization. The `en.lproj` folder stores resource files for English localization,If you localise for french language too, then `fr.lproj` folder will be added and is for French localization. If you look into both folders, each one contains the image file. Download the French version of the cover image from here (or use whatever image you like). Copy the cover image just downloaded and replace the one in `fr.lproj` folder.