"We were talking about this topic in class," she said during an interview with BuzzFeed News.
"I realized that half of the class, the women, knew what I was talking about and lived it on a daily basis. And the other half, the men, didn't even think that this is still happening. They were really surprised and curious. Some of them even did not believe me."
Most of the messages Jansma received have been positive. She also noticed that some men thanked her for opening their eyes to the problem.
But she has also been harassed online.
"I've been called an attention whore or a liar," she said.
Though she has stopped taking pictures, she'd like to hand over the reins to other women, in Europe and around the world, to continue this project.
"I'm not the subject. The subject is catcalling. I also want to show that this happens around the world. But I want to make sure that responsible women do it, because what I do is a bit risky."
This post was translated from French.