Drawing a Frame Pattern on Image using C++ [closed]

I'm writing several functions for my CourseWork and I have the following requirement:

Make a frame in the form of a pattern. The frame is defined:

• Pattern (there should be several to choose from. A beautiful pattern can be obtained using fractals)
• Color
• Width

Briefly, the idea is to learn working with images on the Pixel level, this is my structure of the image (worthy mentioning that I have a lot of helper functions):

struct Image {
    uint8_t* data = NULL;
    size_t size = 0;
    int w;
    int h;
    int channels;
}

I searched a lot on the internet using keywords such as (frame, pattern, algorithm, drawing, image processing), but unfortunately didn't find a satisfying results.

Could you help me please with RESOURCES, IDEAS or ALGORITHM to solve the exercise?