The 20-year-old man, who pleaded guilty to the charge in November, was 16 when the offence took place in 2011, which means his identity is protected by a publication ban under the Youth Criminal Justice Act.
The man told youth court he had apologized to Parsons after he learned the photo, which he had sent via text message to two other girls, had been distributed to many students who attended their high school.
"I realized that I made a huge mistake," he said in a monotone. "Once the picture was sent, I had no control over who sent it and who received it."
He said he had no idea Parsons would endure constant harassment once the photo started bouncing from one student to another.
"I never played a part in the bullying, nor would I," he said. "If I knew what one picture could do, there would not have been that one picture ... This has had a huge negative impact on my life and the lives of those around me. They understand that I was young and I made a mistake."
Parsons' case attracted national attention in 2013 after she attempted to take her own life at 17 and was later taken off life-support. At the time, her family came forward to say cyberbullying had made her life miserable and pushed her to suicide.
Initially, police said they had looked into accusations of sexual assault but after consulting with the province's Public Prosecution Service, they concluded there weren't grounds to lay charges.
However, a week after the girl died, police reopened their investigation after receiving what they said was new information.
Another 20-year-old man charged in the case, whose identity is also protected, was given a conditional discharge in November after he pleaded guilty to making child pornography by taking the photo of the accused.
On Thursday, Judge Gregory Lenehan said Parsons was drinking at a house party with the two other teens in November 2011 when one of the boys took a photo of the other having sex with the girl from behind as she vomited out a window.
In the photo, the boy is smiling for the camera and giving the thumbs-up sign.
Lenehan said Parsons did not know the photo was being taken and did not give consent for it to be shared.
The motivation for sharing the "sexually degrading" photo could have been to brag about a sex act, to embarrass Parsons or both, the judge said.
"While you might have thought it was a trophy moment for you, it was anything but for Ms. Parsons," he said.
"Depicted in that image was a gross violation of the personal integrity and humility of Rehtaeh Parsons."
Before the photo was shared online, Parsons was a "bright, vibrant, enthusiastic teenager," the judge said. Afterwards, "the world for Ms. Parsons became, dark, hopeless and painful."
Lenehan said the accused stole her dignity, privacy and self-respect.
"You knocked that domino over and started cascading events that led to her death," Lenehan said. "Make no bones about it, this was a vile crime. ... You lit the wildfire, so to speak, and it got completely out of control."
Lenehan also ordered the man to attend counselling, submit a DNA sample to the court, refrain from contacting the Parsons' family and not drink or possess alcohol, among other conditions.
Earlier, Parsons' parents read victim impact statements into the court record.
Her father Glen Canning said he wanted to speak on his daughter's behalf, imagining what she would tell the court if she were still alive.
"The week this happened, I lost everything," he said. "I lost my dreams, my hopes and my dignity."
Canning said that before his daughter died, she turned to self-harm to deal with her anguish.
"I continually cut myself to let the pain out," he said, again imagining her voice. "In the end, I wrongfully felt that I became a burden to those who cared for me."
Parsons' mother Leah said she had promised to protect her daughter, but her efforts fell short amid so much pain.
"I did not foresee that I would have to shield her from such cruelty," she said. "I tried to console her, but she crumbled emotionally. ... The cruelty she received would have been too much for an adult, let alone a child."
The girl's identity was protected by a statutory publication ban but her parents pushed to have her name released, saying they wanted her story and her name to be shared widely.
Last month, Nova Scotia's attorney general issued a directive saying breaches of the ban would not be prosecuted unless her name was used in a derogatory way.
A review will soon start to examine how police and prosecutors handled the girl's original allegations.
— Follow @NovaMac on Twitter.
Note to readers: This is a corrected story. A previous version had the incorrect day in the first paragraph
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