Sitting on his porch in Teshie near Accra, Heavy J dipped a brush into red oil paint and dabbed it carefully on to his canvas – a flour sack – adding blood to a knife being wielded by a man. Higher on the canvas, he had started on an outline of a skull.

Heavy J was creating a poster, but not as you might have expected for a horror film. Instead, it was for the animated fairytale The Little Mermaid. The man with the knife wasn’t a killer but the film’s kind-hearted prince, Eric. The skull was also unrelated to the story. “We add more to make people interested,” said Heavy J, whose real name is Jeaurs Affutu.

Hand-painted film posters by local artists were a hallmark of Ghanaian film culture from the late 1970s to the early 2000s, used to advertise screenings for neighbourhood venues known as video clubs after organisers realised that the original posters were not attracting audiences.

Plot lines were regarded as little more than jump-off points for humorous and surreal flights of fancy. Artists working for different video clubs competed to make the best “forgery”, as they described their interpretations.

The practice began to wane around the turn of the century as more Ghanaians gained access to electricity and their own TV sets and video players. Many video clubs went out of business and painters pivoted to create other work. But by then the posters had attained global interest, popularised in books and foreign exhibitions, and old and rare paintings became prized collectibles.

There was a lull in interest in newly painted posters in the early part of the 21st century, but demand has risen, driven by online marketing and a receptive customer base of film lovers in the west.

Deadly Prey Gallery has been working with artists to preserve the culture of making hand-painted film posters, while helping meet the increased demand.

Named after an action film, the business was co-founded in 2012 by Robert Kofi, a Ghanaian who, as a child, used to work as a “hype man” for video centres in his home town of Winneba. He later started collecting and selling posters, then set up the business with Brian Chankin, then a video rental store owner in Chicago, after selling him some works.

Deadly Prey Gallery works with 15 artists, including Heavy J, who has been painting posters for four decades, connecting them to online customers and shipping the artwork on completion.

Most orders come from the US, Kofi said. Old action, science fiction and horror films have the highest demand. Popular titles include The Exorcist and the Star Wars and Terminator franchises. And prices for commissioned pieces start at $600 (£450).

Kofi, who is based in Accra, is part manager and part editor. He identifies the artists most suited for each work, shares his vision of the posters with them and makes regular visits to their workspaces to review works in progress.

In a studio in Ashaiman, 11 miles from Heavy J’s house, another artist called Stoger was working on two commissions: one for the horror film Poltergeist, and another for the 1997 experimental drama Gummo, which contained multiple acts of violence against cats and a scene in which a character eats spaghetti in a bath tub.

The poster showed three cats and a man in a bath with a plate of spaghetti in front of him. In his feedback that day, Kofi, speaking in Ga, a primary language of Ghana, told Stoger two of the cats were not aggressive enough and the food was too clean. “I want uglier cat scenes,” he later explained. “The spaghetti has to be dirtier.”

Stoger, born Benjamin Amartey, was a sculptor before developing an interest in films and becoming a poster painter in 1992. “I use my imagination to make scenes that will attract people so that they’ll love the poster,” he said.

The emphasis on exaggeration comes from an African tradition of “visualising the invisible”, said Joseph Oduro-Frimpong, the director of the Centre of African Popular Culture at Ashesi University and a poster collector himself.

“The posters’ audiences have not seen the film, so it’s impossible for them to know [whether they are accurate]. Therefore, the artists tap into what they call imaginative painting,” he said. “They will highlight these things and in doing so they incorporate things that are not in there. There is a kind of sensationalism to it.”

The reinterpretations at times resulted in threats, insults and even physical attacks from viewers who felt duped. Kofi laughed when he recalled an incident in the 1990s when people beat him up after they watched the action film Double Impact and realised it did not have a scene showing Jean-Claude Van Damme carrying out a beheading, as was illustrated on the poster.

At the Centre for National Culture in Accra, dozens of colourful posters from Deadly Prey Gallery are pinned on wooden walls. They include Jennifer Lopez launching an arrow at a snake in Anaconda, and a mouse coming out of Jamie Lee Curtis’ mouth in Halloween.

“We are preserving a tradition,” Kofi said of the poster-painting craft. “We are preserving a history.”