This is a program in the Processing language that creates image height maps from JPG and other supported file formats. It has decimation with averaging and a dots per inch adjustment, plus you can change the input filename to match your photo.
Note that it does not make a 3D version of the image, it just makes a box for each pixel and sets the height to each group of pixel's average intensity. The result, for the image shown does look a bit like a 3D image of my friend because her face is light and her hair and eyes are dark.
The purpose of this program is to create a sort of 3D printed image braille especially for blind and visually impaired people. You can make art, street signs, business nameplates, etc. that are readable with fingers. In fact, why are we printing street signs within reach any other way?

You need to be familiar with the Processing programming language, know someone who is, or get that way yourself to run this code. Go to www.processing.org to learn everything Processing.
Your image goes in the sketch's data folder, you set your parameters at the top of the file, and the result is written out as output.obj in the sketch's folder. Some tweaking may be required to get the dots per inch and the decimation correct for your intended purpose. Enjoy!