He later pleaded guilty to the charges in June after being apprehended.
Millar - a patched Killer Beez gang member, according to court documents - was in an on-off relationship with the victim.
On July 25 last year, she called it off.
Two days later, when she picked Millar up to take him to a meeting with Probation, he lashed out.
The man told his partner there was a gang ''hit'' out on her and laughed at her.
Millar then punched the woman in the face as she drove along Cumberland St.
When she pulled over, he punched her again, before she bolted from the vehicle.
Judge Ingram said the description of the victim's injuries did not do justice to photos he had been shown, ''which show unequivocally a pretty serious assault on this young woman by you''.
Defence counsel Brian Kilkelly said his client was going through the trauma of losing his father at the time and had unresolved anger issues.
Millar unleashed his wrath online two days later.
He accessed the victim's Facebook account and posted seven photos of her naked.
They were accompanied by comments in the ''modern vernacular'' inviting men to have sex with her, the court heard.
''Those were photos she didn't know anything about. He put them on her Facebook page where all her friends and family are going to see it,'' the judge said.
''It's revenge porn, effectively.''
Judge Ingram said it was hard to imagine a worse case under the relatively new Harmful Digital Communications Act.
Despite that, he noted it was clear the victim still loved Millar and wanted to support him.
Kilkelly invited the court to break the cycle his client had perpetuated for many years - ''prison, out, offending, prison''.
But the judge said it was too serious for anything less than a jail term.
He underlined Millar's criminal credentials, which included more than 100 convictions, 24 of which were for breaching court orders.
''You're a young man who's made a mess of your life. You can do much better than this,'' he said.
Millar was sentenced to two years and five months' imprisonment.
