Urgent Task - Need function to convert 24 bit image to 8 bit image for Node Js application

Hi, I am looking for backend Node js Developer to create function which will take 24 bit / 32 bit, bitmap or png image and reduce its bits per pixel to 8 bit. Image will contain colors black, white and red only. This should be done with Node Js only. Function should work on Node js version 8.11.1 or higher. Attached are the files which should get converted into 8 bit. The clean and well commented code will be appreciated.