The perfect bikini body once required months of disciplined dieting and regimented workouts. Now all it takes to achieve one is a few seconds and a smartphone.

An app called Facetune has made photo retouching a cinch for even the most novice of editors. With a simple tap, drag or pinch of the fingers, users can instantly score an hourglass figure — prompting droves of fame-hungry Instagram entrepreneurs to go under the digital knife.

“Everyone’s editing their photos. If they tell you they’re not editing their photos — if they tell you they’re not using Facetune — I’d laugh at them,” says Thania Peck, who boasts 122,000 followers on her fashion- and beauty-focused Instagram, @catcherinthestyle.

“I saw some [influencers] at Coachella in person, and it’s night and day [compared to their social-media feeds],” says Peck, who declined to give her age and admits to sometimes brightening her eyes and darkening her lashes with virtual assistance. “I saw one that I thought was a mom until she turned around and I recognized her!”

The Facetune app has been downloaded more than 50 million times since launching in 2013, according to a rep from the company. Its easy-to-use tools can whiten the teeth, reshape the body and smooth the skin. And while apps such as AirBrush and VSCO also give users the power of professional-level photo retouching, Facetune is winning the popularity contest: The $3.99 version was the most-downloaded paid app of 2017.

‘If they tell you they’re not using Facetune — I’d laugh at them.’

Some users insist that their waist-slimming and ab-flattening touch-ups aren’t about vanity — they’re just part of the job.

“I feel like [photo editing is] almost a necessary step to continue your Instagram business,” says Las Vegas-based Catherine Lynn, a beauty queen who posts ads on behalf of brands including Fashion Nova and Flat Tummy Co. She figures that editing her photos saves time and money for her and the companies whose products she shills.

Lynn, who is prone to cinch her waist, add volume to her derriere and digitally apply makeup, tells The Post, “People can call it fake all they want, but in traditional marketing, the ads, commercials and billboards are all Facetuned.”

Part of the reason why photo editing has become so prevalent is because many Instagram users embrace the idea that social media is basically an alternate reality.

“This isn’t real life; this is Instagram,” a France-based influencer who goes by Shaya tells The Post. “I have had success in it because it turns out people don’t really care if it’s real life … People appreciate my transparency when it comes to editing.”

After adding “highlighter” to her face, she’ll elongate her legs and enhance her booty.

“It is surprisingly OK and trendy to have a flat chest, but not the butt,” says Shaya, whose Instagram account, @nxshaya, has 233,000 followers.

Some argue that digital perfection is damaging to the body-positivity movement more recently embraced by the magazine and fashion industries. About 70 percent of Facetune users are women, its rep tells The Post.

“When I was a teenager, it was perfect images in magazines that would leave me feeling negatively about myself,” says Sia Cooper, known to her 1.1 million Instagram followers as @diaryofafitmommyofficial.

“Now we’re all glued to Snapchat, Twitter, Instagram and Facebook 24/7 with a constant stream of what appear to be perfect images from friends, models, celebrities and other influencers.”

Cooper says she once privately used the app to slim her hips and thighs — but after giving birth to her daughter three years ago, she began publicly copping to the practice to set a better example.

She now creates posts on her feed that show her body pre- and post-editing as a warning to her followers that things aren’t always what they seem on Instagram.

“It is so easy to make your butt bigger,” she says. “I just don’t want people to compare [themselves to others]. You just don’t know what’s edited or not.”

Others have devoted their feeds to spreading the word that editing is rampant — and bad for your body image.

“I started to notice that these Instagram models and influencers were editing their pictures, and saw all these comments from girls saying they want that person’s body and would do anything to have it,” the 20-year-old Canadian behind the anonymous handle @exposing__ig_modelss tells The Post. More than 14,000 people follow the account, which calls out celebrities’ virtual body enhancements and looks for telltale signs such as warped backgrounds and shadows.

“It made me so sad because nothing they were seeing is real,” the Instagram vigilante tells The Post. “When [Instagrammers] have a big influence on young girls and aren’t honest about their use of Facetune is where I take issue. I hope [my account] will show people the truth behind Instagram models and how they aren’t perfect and have insecurities.”

‘When [Instagrammers] have a big influence on young girls and aren’t honest about their use of Facetune is where I take issue.’

New York-based model Lacey Nelson, who has more than 40,000 followers, says influencers who rely on apps like Facetune to maintain the appearance of a to-die-for physique are not playing fair.

“It’s a little frustrating,” she says. “Models work very hard staying fit and taking care of their skin [in order to book jobs],” but there are no casting agents examining you in real life if you just post photos online.

Still, she doesn’t completely shun the practice of editing. “I’ll be totally up front: I will do maybe a blemish here and there,” she says.

Some influencers say that going the natural route isn’t always financially rewarding.

Despite not using Facetune, 24-year-old Nanite Jean-Aimee can make up to $1,000 a post and has partnered with brands including Lancôme on her account, @melaninmakeup.

But the NYC-based freelance social media manager says she could earn more followers — and thus more money — if she used the app: “I’ve never really been reposted by a brand, because I don’t Facetune my face and I don’t have the flawless skin,” she says.

But she’s steadfast in her stance, and hopes others will be empowered to put their real faces — and bodies — forward.

“Until brands and influencers start valuing authenticity, and stop using apps like Facetune to edit their bodies and faces past the point of recognition, then the body-positivity movement won’t last,” says Jean-Aimee. “We all need to start being comfortable in our own skin and letting impressionable generations know it’s OK to be you.”