Making an uncompressed JPEG 2000 file

Challenge: Construct a JPEG 2000 image file that isn't compressed. Also, try to do it without spending any money. Overview The flagship feature of the JPEG 2000 suite of graphics formats is the wavelet-based "JPEG 2000 codestream" compression format. This challenge is not to figure out how to make a degenerate form of that format …

Yes, pi is wrong. Sorry about that.

Which is the more fundamental constant: π or 2π? As pi day approaches, I think it's important for everyone to state their thoughts on this contentious matter. Here are the main options: π is more fundamental. (the establishment position)2π is more fundamental. (the progressive position)They're about equally fundamental. (the "both sides" position)Any rational multiple of …

When a world needs a hero

The other day, I was browsing some scans of 30-year-old issues of InfoWorld magazine. As one does. And I happened upon one of the very first advertisements for Norton AntiVirus: What a different world it was back then! The ad is from the inside front cover of the March 11, 1991 issue: Internet Archive linkGoogle …

Formulas for “drop”

This post was inspired by me having watched too many flat Earth debunking videos on YouTube. It's my second such post, though I didn't advertise that fact in my first one: How fast does the Sun move? While I'm pretty sure the Earth isn't flat, I sometimes wish the debunkers -- the round Earthers -- …

Encoding Huffman codebooks

This post will assume you have a basic knowledge of the data compression technique known as Huffman coding. Though maybe, since I'm only concerned about decompression, I should call it something like "bit-oriented prefix codes". Huffman coding is really just one of the algorithms that can produce such a code, but it's the term everybody …

Notes on LHARK compression format

LHARK (with a K) is an old compression/archiver utility for DOS. It is related to the popular utility named LHA (formerly LHarc), but should not be confused with it. You should be able to find a copy of LHARK by searching the web for "LHARK04D". LHARK was developed by Kerwin F. Medina around 1995/1996. It …

The Cleveland baseball team

I see that the Cleveland Indians baseball team is finally going to change their nickname. I think that's probably a good thing. For one thing, the word "Indians" is ambiguous, and you wouldn't want to accidentally demean people from South Asia, when you're trying to demean people from North America. They say they haven't chosen …

The blocksize field in LHA compression format

This post is about the data compression format I'll call "lh5". It is actually a family of formats that includes the compression methods often named lh{4, 5, 6, 7, 8}. It was most notably used by version 2.x of the old LHA/LZH/LHArc compressed archive format. It was used, often in modified form, in a number …

Overview of some simple map projections

Some lists of map projections cover them in a way that I think is more haphazard than it needs to be. This is my attempt at a simple introduction to some map projections. I'll only look at the usual situation, in which we are mapping the surface of a sphere onto a planar map. The …

LZ77 compression prehistory

LZ77 is a widely-used class of data compression algorithms. I'll start with a quick overview of it. Assuming you're compressing a stream of bytes (a "file"), your LZ77 compressed data, at a high level, would contain two possible kinds of instructions for the decompressor: Emit literal: {byte value=A}Copy from history: {match-offset=B, match-length=C} The match-offset may …