Is there any functionality to easily replace images in pdfs?

I'm thinking extract images -> run through jpg size optimizer (eg. mozjpeg) -> replace source image in PDF in order to further optimize PDF size.

The extraction is straightfoward obviously, unsure about replacing. I'm beginning to dig through the golang code but I'm not very familiar with the language. Do you have a simple way in mind? If not, I guess I found the excuse I've been looking for to learn Go...