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
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.
Edit and process text files with sed
The sed utility is very useful for manipulating and processing text files from the command line or in a shell script. Linux and Unix systems should have it installed already, while it can be downloaded for Windows. I use the version that comes with Cygwin. sed stands for “stream editor” and can perform complex operations on text data. This page consists of my own notes on how to use sed but keep in mind that the types of things sed can do go far beyond the examples here.
Convert Excel tables for use with LaTeX
There are many ways to create tables in LaTeX. You can create them by hand or use some program that can save tables in LaTeX format. There are likely converters available for OpenOffice or some of the open source spreadsheet programs. I generally make my LaTeX tables by hand or with Microsoft Excel. On this page I will document methods for converting a table in Excel to a table that can be included in a LaTeX document.