I seriously DOUBT that anyone had the ability to make fake images of the earth back when they first became public.
It is very likely that the first images of a round earth were simply high altitude pictures of the Flat Earth taken with a slight fisheye lens. This would give the desired Curvature of Field effect. No computer is needed for that. The creation of lenses is a technology that dates back to the 1600's.
On another note, I'm surprised that no one has asked how we know so much about the Conspiracy and its origins.
It is little known that for a time, years before the publication of Earth Not a Globe, Sir Samuel Birley Robotham himself had infiltrated of the Conspracy. In 1841, based on his esteemed credentials and educational background, a bright young 25 year old Robotham was invited to join the ranks of the highly exclusive Royal Astronomical Society. At that time the Conspiracy was already at full steam. With dozens of publications on the shelves, the conspirators had created a solid foundation for their Round Earth fiction.
On his first visit to the Royal Astronomical Society Robotham discovered to his amazement that the conspirators themselves seemed utterly convinced of a Round Earth. As a product of decades of self deception and self convincing, the belief of a Round Earth was set in stone among each of the society’s members. No amount of inquiry or questioning could persuade the beliefs of a Round Earther. Robotham was completely out of place, a stranger in this environment of sheeple. Even in the year 1841 the belief of a Round Earth was as dogmatic as a religion.
But deep down the conspirators knew the truth, however. They knew exactly what they were doing. Each of the conspirators knew in their hearts that the world flat and that stars were small bright motes a few thousand miles from the earth. But a dull universe doesn’t sell books. A dull universe doesn’t afford the luxury of a sprawling estate. The public at large desires a vast complex universe full of mystery and magic.
Robotham learned, after gaining the trust of a few conspirators, that the round shape of the earth stemmed from the early necessity to fabricate a mysterious force that could turn down into up and up into down. A mysterious force that could imply the absurd notion that Australians hung upside down from their feet. It was the sort of theory designed and calculated for the public to throw money at. The sort of theory that could win a royal science grant from an amused king. Warping the earth into a ball and creating the ficticous force of gravity was a theory born of pure greed.
It was at that point Sir Robotham dedicated his career to exposing the truth about the world. Through eight years of laborious study and experimentation Robotham was able to demonstrate, through various proofs and observations, that the true shape of the earth was that of a flat disk. He published his findings in a book called Earth Not a Globe in 1849. Later he published a second edition in 1865, and a third edition in 1881. Rowbotham and his followers gained notoriety by engaging in raucous public debates with leading scientists of the day. One such clash, involving the prominent naturalist and conspirator Alfred Russel Wallace, led to several lawsuits for fraud and libel.