I have been waiting for this day for 17 years! Today, United States Patent 5,404,140 titled “Coding system” owned by Mitsubishi expires, 22 years after it was filed in Japan.
Why the excitement? Well, 17 years ago, I wrote JBIG-KIT, a free and open-source implementation of JBIG1, the image compression algorithm used in all modern fax machines. My software is about 4000 lines of code long (in C), and only one single “if” statement in it is covered by the above patent:
if (s->a < lsz) { s->c += s->a; s->a = lsz; }
And sadly, there was no way to implement a JBIG1 encoder or decoder without using this patented line of code (in some form) while remaining compatible with all other JBIG1 implementations out there. (more…)