Peter Yu
Peter Yu is a research and development professional with expertise in image processing, remote sensing and computer vision. With an educational background in systems design engineering and considerable research and development experience in industries ranging from district energy systems to medical imaging to cinematic visual effects, he is always looking for interesting problems to solve with significant real-world applications. This is his personal website where you can learn about his research, see some of the 3D and CG artwork that he works on in his spare time and read some helpful tutorials he has written. → More about Peter
Email: [user]@[host] where [user]=web and [host]=peteryu.ca
New and Updated Pages
LaTeX script styles for math
When I was writing a paper, I needed a lot of mathematical variables. I had already used up so many letters in both plain text and bold face that I needed more styles for English letters. So I looked for ways of using different types of script styles in LaTeX equations. I already knew about \mathcal, which is used for math calligraphy but it only supports upper case letters when I really needed lower case variables. It turns out that a lot of the script styles in math mode are upper case only. I eventually found several ways of using lower case script letters in LaTeX equations, as well as a few other math mode styles that seem useful. I have listed them in this short tutorial.
Using Grep
This page is where I consolidate all my notes on the grep tool, which is available on Linux and Unix, and also on Windows as part of Cygwin. I usually use it on Cygwin, so these notes apply to that version of grep.
LightWave surfaces with the node editor
The nodal surfaces in LightWave are pretty neat and allow for some complex surfaces to be made. Surfacing like this is still quite new to me so I am going to start documenting the node set up for some surfaces here on this page. There probably will not be too many surfaces here (not enough time for 3D!) but I will add to it from time to time.
Track changes and highlight revisions in LaTeX documents with latexdiff
When several authors are editing a paper, it is sometimes necessary to quickly highlight what changes have been made in a particular version of the paper compared to previous versions. Word processors have long had revision tracking features for this but some LaTeX authors are unaware that there is a handy utility called latexdiff that can also highlight changes between two revisions by comparing two LaTeX documents:
Interleaving multi-channel images & 3 dimensional matrices in MATLAB
In image processing, images can have multiple-channels. RGB images have three channels and remote sensing data can have many bands. These images can be stored as a three dimensional array in MATLAB, with the first two dimensions representing raster coordinates and the third dimension representing the channel. These 3D arrays might look like this:
| Channel 1 | Channel 2 | Channel 3 | |||
|---|---|---|---|---|---|
| A1 | A3 | B1 | B3 | C1 | C3 |
| A2 | A4 | B2 | B4 | C2 | C4 |
Each channel is a two dimensional array but these are stacked together in a 3D array in MATLAB. The channels in these 3D arrays can be interleaved so that the entire 3D array is stored as a 2D array with the use of the permute function (kind of but not exactly like band interleaving for remote sensing images). I came up with this when I was thinking of ways to make coding an image feature extraction algorithm easier by putting all the bands into the same 2D matrix.