ImageMagick resize with preserve aspect ratio.

ImageMagick is used to change images.
In this case, I will show how to resize images and preserve aspect ratio:
...with height: 600 pixels

convert  -resize x600 *.png

...with width: 600 pixels

convert  -resize 600x *.png

If you know more about ImageMagick send me one email.

Linus Torvalds - kernel 3.7 is now out.

From: Linus Torvalds <torvalds <at> linux-foundation.org>

Subject: Linux 3.7

Newsgroups: gmane.linux.kernel

Date: 2012-12-11 03:59:50 GMT (9 hours and 45 minutes ago)

Whee. After an extra rc release, 3.7 is now out. After a few more trials at fixing things, in the end we ended up reverting the kswapd changes that caused problems. And with the extra rc, I had decided to risk doing the buffer.c cleanups that would otherwise have just been marked for stable during the next merge window, and had enough time to fix a few problems that people found there too. There's also a fix for a SCSI driver bug that was exposed by the last-minute workqueue fixes in rc8. Other than that, there's a few networking fixes, and some trivial fixes for sparc and MIPS. Anyway, it's been a somewhat drawn out release despite the 3.7 merge window having otherwise appeared pretty straightforward, and none of the rc's were all that big either. But we're done, and this means that the merge window will close on Christmas eve. Or rather, I'll probably close it a couple of days early. For obvious reasons. It's the main commercial holiday of the year, after all. So aim for winter solstice, and no later. Deal? And even then, I might be deep into the glögg. Linus

Read more here.

Simple convert images using ImageMagick - convert features

Can be done by using ImageMagick.This is a software suite to create, edit, compose, or convert bitmap images. It can read and write images in a variety of formats over 100. Using ImageMagick let you resize, flip, mirror, rotate, distort, shear and transform images, adjust image colors, apply various special effects, or draw text, lines, polygons, ellipses and Bézier curves.
Install the software under Fedora:

# yum install  ImageMagick 

Convert an image from one format to another. In this case jpeg.

$ convert *.png *.jpg

$ mogrify -format png *.jpg  

Read more about this software here.

News: Unusual commands in linux : pv

Today I will speak about pv command.
Pipe viewer - pv is a terminal-based tool for monitoring the progress of data through a pipeline written by Andrew Wood
To install pv on Fedora or CentOS do this:

$ sudo yum install pv

You can read the man file to get more help:

man pv

The result is:

NAME
       pv - monitor the progress of data through a pipe

SYNOPSIS
       pv [OPTION] [FILE]...
       pv [-h|-V]

DESCRIPTION
       pv  allows  a  user  to see the progress of data through a pipeline, by
       giving information such as time  elapsed,  percentage  completed  (with
       progress  bar),  current  throughput  rate, total data transferred, and
       ETA.

       To use it, insert it in a pipeline  between  two  processes,  with  the
       appropriate  options.  Its standard input will be passed through to its
       standard output and progress will be shown on standard error.

Let's see some examples.
You can get precise time how long it will take.

$ pv voronoi.py | python 
 737B 0:00:00 [86.9kB/s] [==================================>] 100%

You can see how fast the computer reads from /dev/zero.

$ pv /dev/zero > /dev/null
1.1GB 0:00:05 [   2GB/s] [    <=>                                            ]

You can use the dialog to show a progress bar.
To do this you need to use -n arg.

$ (pv -n /dev/zero > /dev/null) 2>&1 | dialog --gauge "Please wait" 10 70 0

Make one simple kernel module using C programming language.

Today I will try to explain how to make a kernel module.
Basically, a kernel module it's one piece of code that can be loaded and unloaded into the kernel.
You can read about kernel modules from here.
Now, let's try to make a simple kernel module.
Writing your own module can be done if you know some basic rules.
First, about how to use modules.
Suppose you have a new module named kernelmoduletest.
How to load the module.
Just use this command in your module kernel folder:

#insmod kernelmoduletest.ko

Next, test the kernel module messages.
This can be done with:

#dmesg | tail

Also, you need to remove the kernel module.

$ rmmod kernelmoduletest 
ERROR: Removing 'kernelmoduletest': Operation not permitted

This means you need to have superuser rights. So use the sudo or su command.
Then use the rmmod command.
Know how to make the kernel module skeleton.
This is not very simple because you need to know many things about kernel and programming.
But you can try the test with some simple example like this example:
Create the c file named kernelmoduletest and add this source code:

#include <linux module.h="">
#include <linux kernel.h="">

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("kernelmoduletest");
MODULE_AUTHOR("Catalin George Festila/mythcat/catafest");

int init_module() {

    printk(KERN_INFO "Now I will initialize my  kernel module\n");

    printk(KERN_INFO "Test: Hello World !\n");

    return 0;
}

void cleanup_module() {

    printk(KERN_INFO "Bad!... kernel module unloaded.\n");
}</linux></linux>

Make a new file named Makefile.
Add this to tell how to compile the kernel module.

obj-m += kernelmoduletest.o
all:
 make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
clean:
 make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

Compile your kernel module
Just use make command.

# make
...
  Building modules, stage 2.
  MODPOST 1 modules
...
make[1]: Leaving directory `/usr/src/linux-headers-2.6.31-14-generic'

If you test your module using the commands from the top of this tutorial, you can see that:

[14694.779227] Now I will initialize my  kernel module
[14694.779233] Test: Hello World !
[15049.825605] Bad!... kernel module unloaded.

If you have already made kernel modules and the subject it's interesting for you, send me an email.
Thank you. Regards.

News: Tips and tricks: watch and cat.

Sometimes it is necessary to find solutions.
Today's example involves two Linux commands:
watch and cat
Here is a simple method by creating a script that returns an output:

while [ 1 ]; do cat /proc/meminfo; date; echo; sleep 1; done

Make this script executable and name it: meminfo.
The output is then processed by the command:

$ watch -d ./meminfo 

This simple method can be applied to other files ...

Using SL4A bash shell script to connect Linux with Android tablet .

Using Linux with Android OS is very simple.
I install the next two android application: sl4a_r6.apk and PythonForAndroid-r7b1.apk.
Use the PythonForAndroid-r7b1.apk just if you want to write some python scripts.
We can download it from here.
The first: sl4a_r6 it's used to write and run scripts like bash shell, HTML, Java, Python.
With this, the SL4A provides and make APIs available via JSON RPC calls.
The PythonForAndroid-r7b1 allow you to install python modules...
We can read more on this website.
Let's start with one simple bash shell script.
We will make a shell script to test the connection between Linux and Android tablet.
The connection will be through a wireless router that has opened the port through which the communication.
Tablet has Android 4.0.
We use the Linux command NC, see: nc command.
This is the script on the tablet and it will run first.

nc -l -p 7000

See the next image:

Button 1 - run the script
Button 2 - edit the script
Button 3 - save the script
Button 4 - remove the script
Use the next command with your IP on the Linux terminal.

nc xxx.xxx.xxx.xxx 7000

If you type something in your terminal you will see on a tablet.
The input from my linux terminal can be seen in the next image:

Ant this is the output on my tablet.

We can test multiple features of command nc.
I'm just curious if you have some new ideas on this subject.

News: New GTK3 theme make your Linux to look like an Android

The new GTK3 theme inspired by Android will make your Linux nicer.
reNIX Gnome Shell theme: [link]
reNIX (for Chrome/Chromium): [link]

News: About light laptop with your Linux distros.

ZaReason is launching a thin and light laptop called the UltraLap 430.
Linux computer builder has all the specs you’d expect from a modern ultrabook.
Prices start at $899 and it's available now from the ZaReason store.

Features:

• 14.1" HD (1366x768) Glossy LED Backlit Display
• 3rd Generation Intel Core Processor
• Intel HD 4000 Graphics
• Quick performance and power-on times with Solid State Disks
• HD Stereo Speakers
• 802.11 B/G/N WiFi included
• Bluetooth
• 3 in-1 card reader -- SD/MMC/MS supported
• 1.3 Megapixel HD webcam included
• Multi-gesture touchpad

Ports:

• HDMI port
• Gigabit Ethernet port
• Kensington lock port
• Headphone/Mic Jack
• 2 USB 3.0 ports
• 1 USB 2.0 port

Specs:

• Your choice of a variety of Open Source operating systems, like Fedora 17
• Battery Life: Up to 6 hrs
• Dimensions (WxDxH): 13.5in x 9.25in x .75in
• Weight: ~3.5 lbs

News: Google Translate Android can translate from pictures.

News about Google Translate Android.
Use camera to take a picture and brush text to translate - available on Android 2.3 and above.
Get instant translation results as you type.
Choose dialect preference for speech input.
Japanese handwriting now recognizes multiple characters at once.
Added access network state permission to check network availability when sending requests.
Try this on play.google.com

OpenGL Driver support for Linux and Windows.

NVIDIA has released a set of OpenGL 4.3 drivers for Windows and for Linux.
The driver support provides beta support for OpenGL 4.3 and GLSL 4.30 on capable hardware.
For Linux, the version number R304.15 is not the same with the drivers for Windows: R305.53.
All ARB extension specifications can be downloaded here: this page.
For OpenGL 4 capable hardware, these new extensions are provided: ARB_compute_shader ,ARB_multi_draw_indirect ,ARB_shader_image_size ,ARB_shader_storage_buffer_object
You can download all drivers from here.

Testing your disks using dd utility and time.

You can execute copies a large block of data to and from disk.

This will minimize disk caching.

Next is one example if our test system has 1GB of RAM.

It is easy ( 1GB = 250,000 blocks ).

$ time sh -c "dd if=/dev/zero of=bigfile bs=8k count=250000 && sync"
250000+0 records in
250000+0 records out
2048000000 bytes (2.0 GB) copied, 37.0113 s, 55.3 MB/s

real 0m40.910s
user 0m0.172s
sys 0m12.641s

It's very hard to argue with this dd test.

Using DIGITAL PEN CAMERA eheV1-USB-II with mplayer

It's not my camera, I take it just to try to make working on Linux OS.
This is the device.

The dmesg tell me about this camera:
uvcvideo: Found UVC 1.00 device USB2.0 Camera
If you want to see and not to take frames, then use :
mplayer tv:// driver=v4l2:width=640:height=480:device=/dev/video0 -vo null
You can try to take some frames. I use this:
mplayer tv:// -frames 10 -tv fps=20:driver=v4l2:width=640:height=480:device=/dev/video0 -vo jpeg
The result is ten frames.
On this image I draw one line to see how working default.

And using the zoom ...