My note on GIMP to edit digital photos

January 30, 2007

Before struggling with Canon EOS 400D or 30D, or … making money first…, I figured out that before I have money to buy a DSLR, I’d play around with digital photo editing softwares in Linux first. I then searched for a good photo editing software for sometime. But a voice told me in my head: “Hey, dude, don’t you know GIMP was in your Ubuntu from the very beginning.” Yeah, I am stupid, how can I ignore such a powerful tool that comes with Ubuntu (in fact, I think most distributions would have it). Then I started to learn it. Here are some notes in case I forget them:


  • Remove red eye. Comes from here. Quick steps:
  1. In the picture window, zoom to the pupils, press “Z”.
  2. Play around the threshold to select red areas.
  3. Filters/Colors/Channel Mixer. Choose around “Red 10%, Green 60% and Blue 30%” , done.
  • Blur background, focus object. Comes from here. Doing this can make my picture more like taken from DSLR. The link shows a wee complicated way, my lazy way is:
  1. Always select object area first. Either use quick mask (Shift+Q, then use white brush to brush areas to select, and black brush to brush unwanted areas, then Shift+Q again to see the selection area), or use keyboard “I” to select.
  2. Use Filters/Enhance/Unsharp Mask to sharp the object a bit.
  3. Ctrl+I. Use Filters/Blur/Gaussan Blur to blur background. (radius around 20 would be OK)
  • Make colors better. This comes from a lot of links.
  1. First of all. Tools/Color Tools/Levels/Auto would be a good automatic way to better color.
  2. If I feel some colors are too thick in the picture (say blue), change chanel in the Levels dialogue from value to that chanel, say blue. and drag the righ triangle to left. Need to play around.
  3. Also /Tools/Color Tools/Curves is worthy playing around. I haven’t figured out the principles of these tools, but they are good…
  4. /Tools/Color Tools/Brightness-Contrast is self-explained.
  5. Tools in /Layer/Color/Auto can also do some automatic jobs to make colors better.
  • Heal picture. This is so amazing. With this Clone tool, I can remove dust in the picture. It can achieve some amazing effect far more than dust removing. Just play around it once, you’ll get the idea.
  1. In the picture window, zoom to the dust I don’t want. keep some good area around it, because clone tool needs place to clone. Press “C” key.
  2. Ctrl+Click the spot you think that is very similar to the dust area that you want to heal. This is the original area to clone.
  3. Click on the dust to heal it with the clone area. Choose proper brush size. Sometimes I find a big fuzzy brush can do better job than small ones.
  4. Notice that if you click hold and drag the brush around the dust area, the original clone area are moving too. This can avoid making picture too fake (all copy from the same spot). There is an option of Alighnment to select, try it, you’ll get the idea.

These are the notes I learned so far. Anyway, GIMP is an amazing free software, I’ll keep learning it:). The picture below is my practice, with my normal Kodak digital camera without flashlight (along with the original picture). First I used Levels and Curves to deal with the color. Then I used unsharp mask to sharpen nemo, then Gaussian blur to blur the background.

Nemo Nemo origin

HOWTO: quick search terminal history commands

January 20, 2007

I like the MATLAB way of input command — it has the same tab-complete feature; in addition, it has a up-arrow-auto-complete-history-command feature. For example, if I have typed a command “x=39;y=23;” before, now I can just type “x” and then type the up arrow button, then this command would auto-complete. It can also switch between all the history commands that has the same starting letters.

Vert unfortunately, I haven’t found any similar feature in the Linux terminal, or say bash. There is a command called “history” that can list all the history commands. I can type “history | grep xxx” to search the command I want to find. The same example, I can type “history | grep x=” try to find that command. There would come up something like “201 x=39;y=23;“. The number in the beginning is the index of in the history. Then I can type “!201” to repeat this command. But I find this quite time-consuming.

Then I came across a shortcut of bash “Ctrl + R“, it can “search through previously used commands”. Say in the terminal I type “Ctrl + R”, then “(reverse-i-search):” came up, then I can type keyword of my previous command, say “x=” then the most related command would come up. After the right command comes up, then type enter, finish. Although not as convinient as the MATLAB mode, this is way better than using “history” command, in my view.

HOWTO: make vim latex-suite always recognise tex file

January 9, 2007

Although the KDE latex tool Kile looks very nice to me, I like use the famous vim editor with its latex-suite to edit my latex files. I got a problem with this editor recently. The problem is that vim can’t invoke my tex file automatically. For instance, there is an empty file called “empty.tex”. If I open it with vim, the latex-suite won’t load automatically. As long as I added some latex keywords like “/usepackage”, vim would recognise this file as latex tex and load the latex-suite.

I searched the vim “filetype plugin manual” and got —

Vim can detect the type of file that is edited. This is done by checking the
file name and sometimes by inspecting the contents of the file for specific

So it seems that vim detect the latex tex file by the content of the file, not the extension name “tex” . After some searches, I found there are three ways to make sure the latex-suite will be loaded if the file have a tex extension name.

  1. In the vim when edit the file. Use “: set filetype=tex
  2. Put this line “/* vim: set filetype=tex : */” in the file.
  3. vim ~/.vimrc. add this line: “let g:tex_flavor = “latex”“.

I think the last method is the best.

No more Fedora Core?

January 6, 2007

I ran across this RSS title from this morning. Feeling sad for FC, which is my first Linux distribution. I was attracted by the blue-style of FC before touching Linux. However, a close look into the article seems this a “joke”, here is the link.

Starting with Fedora 7, there is no more Core, and no more Extras; there is only Fedora. One single repository, built in the community on open source tools, assembled into whatever spins the Fedora community desires.

Is this a word game just like rename “Fedora Core” into “Fedora”? At least, it seems nothing differnt to me. I think there is one thing for sure, there is no more the name of “Fedora Core”, not Fedora Core.

Tomboy icon on the KDE tray, finally

January 5, 2007

Tomboy is a nice note taking application that I am using it everyday. But it is really annoying that no icon is there on the KDE tray. But it is really there, like a transparent icon. These problem seems a bug in the 0.4 release, because I saw someone else got the same question in some forums. But now with the 0.5.1 release, the tomboy icon finally can be displayed on the KDE tray. Of course there are other new features, please check here.

Tomboy icon on the KDE tray

Superswitcher — A nice Alt+Tab alternative

January 5, 2007

Today I came across a nice small application called “Superswitcher” from LinuxTOY. It is quite handy to use Win+direction keys to switch from desktops and applications in one desktop.

“SuperSwitcher is a (more feature-ful) replacement for the Alt-Tab window
switching behavior and Ctrl-Alt-Left/Right/Up/Down workspace switching behavior
that is currently provided by Metacity.”

Don’t worry about the homepage of Superswitcher is inside the Gnomefile, because I found it works perfectly in my KDE desktop environment. It also has some other features like move windows, find particular windows by key combinations. The only problem I found so far (after trying 2 min only…) is that it conflicts with my KDE shortcut. I have Win+ KEY to open applications, and Win+Ctrl+KEY to switch to that window. Now I can’t use them if I have Superswitcher on. I’ll try to find a way to overcome this…

A screenshot here:

HOWTO: backup my Ubuntu

January 1, 2007

This is a short guide to my backup scheme. I use this nice guide from the ubuntu forum. First of all, I found it will take ages to extract some certain file from the huge tar file of the whole system backup. So I backup separately. The idea is to backup the home folder into 3 files, and other system files into one. Here they are:

  • tar cvpzf /media/SEA_DISK/Backup/Linux/Wei/personal_111206.tgz /home/wei/personal This backup all the personal files include my pictures and application files (say KmyMoney file).
  • tar cvpzf /media/SEA_DISK/Backup/Linux/Wei/samba_111206.tgz /home/wei/samba
    This backup the samba folder, which is used to share with my Windows XP via VMWARE. Yeah, I am still usingWindows XP, unber VMWARE. I have to use windows to do some study. This folder is shared between Ubuntu and Windows XP so that I can save the data file in Windows and edit my paper in Ubuntu with just “Ctrl+Alt” to switch out VMWARE.
  • tar cvpzf /media/SEA_DISK/Backup/Linux/Wei/wei_others_111206.tgz –exclude=/home/wei/personal –exclude=/home/wei/samba –exclude=/home/wei/songs –exclude=/home/wei/vmware /home/wei
    This backup all the other files in my home folder except the”song” folder, which stores temporary mp3 files I copy from my external hard disk occasionally.
  • tar cvpzf /media/SEA_DISK/Backup/Linux/system/system_edgy_kde_111206.tgz –exclude=/proc –exclude=/lost+found –exclude=/mnt –exclude=/media –exclude=/home / This backup all other system files.
  • One very IMPORTANT hint: don’t add the last “/” symbol in the exclude parameter. For example, write “–exclude=/home”, but NOT “–exclude=/home/”. Maybe this is a tar bug. /media/SEA_DISK/ is the mount folder of my external hard disk. 

Just these simple steps to backup my Ubuntu, with no need to boot by a CD using Ghost. This is done in running Ubuntu. Amazing, isn’t it? I haven’t restored my Ubuntu yet, but it is just unpack this tar files, again, in the running Ubuntu. In fact, I doubt there wouldn’t be a chance that I have to restore it, Ubuntu seems so stable and easy-repair.