How to Sample the Greyscale Levels of a JPEG File?

Hello all,

please notice the current app that I am developing:

It is based on the app below and is an excellent first project for the novice Three.js programmer mentioned before:

The objective is to mock (in a respectful yet critical manner) the method currently used by doctors to determine whether X-rays are genuine or have been altered. They need to write to the lawyer that represents the victim’s relatives, Paul Kirk, and ask permission to visit the National Archives II, in College Park, Maryland.

Armed with a device called Optical Densitomer, they sample about 11 points of each radiograph. The total output they get out of that room fits in half a notepad page. The most complex operation is a division with a hand-held calculator. That is the state of the art for those practitioners, celebrated book authors. My application will allow pretend MD users to sample only that number of points and chastise them if they attempt to sample more.

In any serious study this should be done with DICOM files used in radiology, but all I have is two JPEG files. The x,y coordinates are trivially easy to obtain but the density (approximated by the greyscale level) is harder.

How should this be done in 2020? Using Digital Signal Processing it is possible to sample millions of points (the resolution of film digitizers is 8K, it takes one hour to scan each piece of film) and determine parameters such as cranium thickness and density.

Hence my mocking when they hit 11.

I am considering Pacman music as audio track.


JFK Numbers

  1. Shouldn’t this be in #jobs category? If you’d like someone to solve the entire issue for you.
  2. If I understood correctly, and all you want to do is to compare 2 grayscale jpgs, you can use pixelmatch. If you’d like to do some manual manipulation or sampling on the jpgs, you can also try jimp. As for the resolution - node should easily handle an 8K image, even pixel-by-pixel sampling won’t take hours unless you output a lot of logs on the go.
1 Like

The question is very clear, in the subject line.

I do not need to hire anybody, as mentioned already. This is a case that has remained unsolved for 6 decades due to information hiding. I prefer to err in the opposite side.

Your answer is great and most appreciated.


JFK Numbers

I do not want to compare anything. I need to retrieve the greyscale level of pixel at location x,y.

Thanks again!

JFK Numbers

We are talking about different “scans”. From film to hard disk takes about one hour and the output is a DICOM file. You can find the device and its specs here: [ZIP file]

That is the most advanced portable film digitizer in the market, Vidar Edge. They are about $21K

This is one of the companies that I approached:

The manufacturer is also assisting me. The interesting question is whether they will put the name JFK Numbers in their client list. Too many people and institutions run scared when I mention the ominous words: “Dealey Plaza”.

My objective is to lobby (read: grab by the collar, shout, humiliate) the so called “leaders” of the community so they put aside their differences and rescue those X-rays from oblivion.

Oh, an anecdote. When I was first tasked to get high tech material, I approached a company specialized in X-ray film digitizing:

[Company Rep:] “Of course we can do it. We have the best equipment”

[Ramon:] “Yes, I saw your web page, but I need an specialist to bring a portable equipment to the locations where the X-rays are located, in Boston and College Park, Maryland”

[Company Rep:] “No, we do not make home visits. What’s the big deal? Just Fedex it. We have years of experience, have processed millions of X-rays. BTW: We provide disposal service, if you need it”

[Ramon:] “The only time those X-rays have left that room was in 1977, under military guard, to a Kodak Laboratory, per orders of the US Congress. I cannot get that”

Those copies are analog, very poor quality.

Thanks again…

JFK Numbers



Pls don’t use my advice to humiliate anyone, thanks… :’)


Humiliate, lobby, entice, woo, lead, cajole, persuade, manipulate : -) same thing.

JFK Numbers

“If the people lead, the leaders will follow”