› Edit pictures » The image viewer can only be used to view pictures; it can't edit them. For that, you must use a picture editing application, like the GIMP image editor. To open a picture for editing in a different application:
Click Image ▸ Open with, or right-click on the image.
Select the application you want to use to edit the picture.
When you are finished editing, save it and close the other application.
The image viewer will detect that the picture has been changed and will ask you if you want to reload it. Clicking Reload will ensure that you are viewing the most recent version of the file.
To delete a picture that you don't want any more, click Edit ▸ Move to Trash, or right-click the picture and select Move to Trash.