As much as I like putting out posts — and I really do — there will be no post over this — Christmas — weekend. You better believe I’ve been doing other things!

I am pretty sure there will not be a post ready in time for next — New Years — weekend.

I hope to resume posting by Monday January 11, but we’ll see. I know what I plan to write up, but there is a lot going on this time of year.

Frankly, I would not have had a post for Dec 20th, except that I deliberately accumulated a backlog. I felt a little bad that the wavelet bibliography was delayed so long, but I was holding it in reserve.

In any case, I certainly expect to resume posting before the end of January.

Happy holidays.

Books Added: Wavelets


I used Hubbard, Frazier, and Nievergelt as introductions. When I last touched wavelets, I was searching through all three of Burrus et al., Strang & Ngygen, and Daubechies to learn more about wavelets. I can’t say I was working through any one of them, but I was certainly trying to find things in all three of them.


Read the rest of this entry »

Color: Cohen’s intriguing F matrix again

Minor edits, 4 Jan 2010.

Let me run thru the derivation of Figure 20 again, still with the CIE 1964 tables, but at 20 nm intervals. Then I show two alternative calculations. And one of them will show us why Cohen switched the sign on f2.

There is interesting linear algebra and vector algebra in this post, even if you’re not interested in where these problems came from.


Read the rest of this entry »


If you just got an RSS feed for a new post, I apologize. I meant to click “Preview”, not “Publish”, and I have taken it back.

It should be ready next weekend. Still, if you want to read what you’ve got, feel free.

Color: Cohen Figure 20, “an intriguing F matrix”

Typographic edits, 4 Jan 2010.

I struggled to make sense of pages 94-101 of Cohen’s “Visual Color and Color Mixture”.

I understand them now. Mostly.

The challenge was to derive a drawing of three basis vectors (Figure 20, p. 95), shown here :

He calls these three vectors both “an intriguing F matrix” and “This canonical orthonormal configuration….” But as far as I can tell, he never said where he got this particular one. He made it sound important, so I had to derive it. Figuring it out, as usual, was very educational.

What follows is a detective story.
Read the rest of this entry »