On my Android it was easy to set up all my photos to back up on Google. To do the same on the iPhone you need to install Google+.
Once you install the Google+ app for iPhone you can them have all your pictures (in camera roll) get saved to Google Drive. To set your iPhone up, start Google+ (and log in) and choose Photo, as shown below.
Next go into 'Camera and Photos'.
Then choose 'Auto Backup' to turn it on.
Lastly, turn Auto Backup on, and I turned on 'Full Sized Backups' so my images would have the best resolution. To save on my data plan I choose to backup photos over Wi-Fi to save some of my data plan bandwidth.
I think that is it....my iPhone now backs up my photos automatically to Google to ensure I have a backup, and so I can access those images on Google and it's apps, like Blogger.
I also created this post in the iPhone Blogger app.