PyQt: power of Python, beauty of Qt

Qt is very powerful tool for GUI programming. But programming using Qt C++ is not always easy because of unavailability of libraries and difficulty in coding. But Python is powerful and has abundant list of libraries related to virtually anything. Some operations in Python is very easy to use. But the problem of Python is that, it has no GUI its own as handy. PyGTK (Python and GTK) and PyQt (Python and Qt) are the remedy. Here I am explaining how to start with PyQt.
PyQt has no support from QtCreator yet, but the features of QtDesigner can also be used for the PyQt coding. This tutorial explains how to start PyQt programming if you are already aware of Qt C++ programming. This is not just a 'hello world' program, but the code will do something and make you capable of coding your own programs.
In this example, we are building a simple GUI with three LineEdit bars and a single button. When the button is clicked, the numbers entered in the LineEdit a and b are added and the sum is shown in the third LineEdit.

First of all, make GUI widget in Qt Designer and rename the objects a, b, sum and pushButton as shown in screen-shot below. Also make a custom slot named calc_sum(). Save and quit the Designer program.

Now you can see the user interface file named 'widget.ui' (the filename may vary if you changed the widget name while creating your project. Anyway, the filename with .ui as extension is the file we need). We need to create the curresponding python file for user interface. In C++, it is done using uic(User Interface Compiler). In our case, in python, we use a utility named 'pyuic4'. If 'pyuic4' will be automatically installed while you install PyQt. If not, especially in Linux, install it from the repository. Then make the user interface file 'calc_ui.py' (or any name you wish. But for the first time use this name to avoid ambiguity) file using the command:

pyuic4 widget.ui > calc_ui.py

This command will generate a new file named 'cal_ui.py'. This is the user interface file only. We are going to make another file 'calc.py' which will handle the core program. Use a text editor and copy the code below:

import sys
from PyQt4 import QtCore, QtGui

from calc_ui import Ui_Widget


class MyForm(QtGui.QMainWindow):
    def __init__(self, parent=None):
        QtGui.QWidget.__init__(self, parent)
        self.ui = Ui_Widget()
        self.ui.setupUi(self)
    def calc_sum(Widget):
    value1=Widget.ui.a.text();
    value2=Widget.ui.b.text();
    result=float(value1)+float(value2);
    str_result=str(result)
    Widget.ui.sum.setText(str_result);


if __name__ == "__main__":
    app = QtGui.QApplication(sys.argv)
    myapp = MyForm()
    myapp.show()
    sys.exit(app.exec_())

Save the file. Then run the file:

pyhon calc.py

I am not so good in explaining the code. I think you got the idea of how to make a custom slot and to make a standalone program. If any reader need clarification or more explanation, I will try to explain further.

Qt Programming in Malayalam Part-2

Before reading this tutorial, read my previous post "Qt programming in Malayalam" if you have not read it yet.
    Have you ever wonder about easy switching from English to other languages such as French, Spanish etc. in software applications? Even though Malayalam switching is rare, translation is possible in Malayalam as well like any other language. Qt provides an easy way of language switching by means of Qt linguist. This tutorial describe how to build a Malayalam switchable application in Qt. An easy to start tutorial is packaged with Qt Help itself. Here is a quick tutorial of how to build a Malayalam application if you have the source code of the English version. Before we start, I assume:
1) You have Qt installed in your PC.
2) You have a very basic knowledge of Qt programming. How to compile, build and all.
    If the above is not qualified, sorry, it is better to pause here and read this and resume. Suppose you have a Qt application in English (If you have not your own, a lot of examples  are there in qtdir/qt/examples. (qtdir is the directory where you installed Qt). For better understanding, I prefer an application named 'QMusicPlayer' from examples(qtdir/qt/examples/phonon/qmusicplayer). You can take other examples as well. Open qmusicplayer.pro using Qt, then build and run it. You will get a minimal musicplayer in English. Now our aim is to make the malayalam version of the same application.

Now we need to edit two files 'main.cpp' and 'qmusicplayer.pro' as follows:

main.cpp

#include

#include "mainwindow.h"
#include

//![1]
int main(int argv, char **args)
{
    QApplication app(argv, args);
    QTranslator translator;
    translator.load("malayalam");
    app.installTranslator(&translator);
    app.setApplicationName("Music Player");
    app.setQuitOnLastWindowClosed(true);

    MainWindow window;
    window.show();

    return app.exec();
}

qmusicplayer.pro

QT        += phonon

HEADERS   += mainwindow.h
SOURCES   += main.cpp \
             mainwindow.cpp
TRANSLATIONS = malayalam.ts

# install
target.path = $$[QT_INSTALL_EXAMPLES]/phonon/qmusicplayer
sources.files = $$SOURCES $$HEADERS $$FORMS $$RESOURCES *.pro *.png images
sources.path = $$[QT_INSTALL_EXAMPLES]/phonon/qmusicplayer
INSTALLS += target sources

wince*{
DEPLOYMENT_PLUGIN += phonon_ds9 phonon_waveout
}

symbian:TARGET.UID3 = 0xA000CF6A

Changes made in the code are highlighted. The changes in code simply add a Translator feature to your application. While running, your application will seek a file named 'malayalam.qm' which contains one to one translation of all English words used in program to Malayalam. 'malayalam.qm' is a binary file and is to be generated from a file named 'malayalam.ts'. This file is automatically generated using the command in terminal:

lupdate -verbose qmusicplayer.pro

Then the newly generated file - 'malayalam.ts' can be seen in the project directory. But it is an empty file and we need to update that file with all one to one translations. To do so, open the file with Qt linguist:

linguist malayalam.ts

If you couldn't find any command like 'lupdate' or 'linguist', most probably, you have not added the qt directory to the PATH. To do this use the following command Linux,

PATH=$PATH:qtdir/qt/bin/

directory may be different and must change it as your needs. Then use 'lupdate' and 'linguist'. If you are still stucked, check whether you completely installed Qt SDK. In Windows, if you are using Qt enabled prompt, I hope there will be no any problem.

    Now I assume you opened 'malayalam.ts' successfully in Qt Linguist. It shows all english words which translation is enabled. (Refer fig). Click on each english word in 'Source Text' list and add curresponding Malayalam translation in the 'English Translation' edit box at the bottom (highlighted on figure). Repeat the process for all words and save. Then File->Release. It will generate the binary file 'malayalam.qm' in the same directory.
    Now run the qmusicplayer application with file 'malayalam.qm' is placed in the same directory of the executable. Now you can see the malayalam version of 'qmusicplayer'.

In the absense of the file 'malayalam.qm', there will be no run time error in the program, it simply shows the english version. Similarly you can build a multi-lingual swithable version.

How to heal? Some keyboard keys are not working

It is a common problem that failing some keys in PC keyboard. But it become cumbersome while you type anything seriously. Replacing or repairing keyboard is not always easy, especially you are using a laptop. The seriousness of the problem depend on the failed key operation. If ENTER, DELETE, SPACE, SHIFT, CTRL, ALT etc are failed, your keyboard is almost at the worst state. Here I am trying share how to dilute this key failure effect.

Method 1 - On screen keyboard(Quickest way)
If you are doing something seriously, and don't have enough time to dismantle keyboard and clean, best method is to use virtual keyboard. On MS Windows, it is built in. You can access it by,
Start - All Programs - Accessories - Accessibility - On-Screen Keyboard
The fundamental advantage is that it is independent on how much keys in your keyboard are failed. Also you can access and use this utility completely using your mouse. In Linux, there is a similar utility named 'onboard' (use command 'onboard' to open it) and most probably it is built in. But it considerably lowers the typing speed.


Method 2 - Key mapper (Quicker enough)
SharpKeys from RandyRants is a good utility (for windows) to assign function of one key to another key. It can be done using a registry hack, but using Sharpkeys is a handy method. A good number of keys are there in your keyboard which are rarely or not used at all. Function keys F1, F2 ..., Win Key, Home, End, Print Screen, Pause/Break. If you use only left or right CTRL key is using other can be contributed for other function, because right and left CTRL keys are considered different. The same is applicable to SHIFT and ALT. Although this method slightly lowers your typing speed, you can still do everything.


Method 3 - Cleaning
Open it, clean well. If you are lucky, it will give life to your keyboard (I am unlucky).


Method 4 - Repair or Purchase
This is the last way. Of course, result will be positive.

LED Matrix pattern designer

LEDmatrix pattern designer is a tool used to generate matrix(2D) patterns in hex numbers for displaying LED matrix using a micro controller.

It is based on Qt framework and hence cross platform. It supports up to 16x16 matrix size. You can increase it by making minor changes in the sourcecode, but 16x16 is enough for most cases. This is done from the same pace of my previous project - ChaserDesigner. Only you need to do is that, specify the 2D pattern either manually or using the enhancing tools provided by the software. Then you can generate it's hex equivalent by a single click. A 2D pattern can be scanned either horizontally or vertically. The scanning mode can be switched in the software while making frames.

I think most of the features of the software are self explanatory. If you have any doubts, please comment. All files associated with this project are free to download.
Project source(Linux, Windows)
Windows executable
Required dlls for Windows executable

How to make bitmaps for graphic LCD (glcd)?

Making bitmaps for graphic LCD is pretty easy. There is a lot of free tools available over Internet, but I think there is no need to download them if you have already installed an image editing software in your PC. Also it is interesting to know what's actually they do. In this quick tutorial,  an example using GIMP - a free image manipulation program is described. This is a general tutorial and can be applicable for almost all type of graphical LCDs.

Step1: Know the pixel size of your graphic LCD. For KS0108 (a general purpose glcd), it is 128x64.
Step2: Choose an image(any image) to be embedded on LCD.
Step3: Scale the image to 128x64. In GIMP, (menu)Image -> Scale Image. Change height to 64 and width to 128.
If your image is not an exact multiple of 128x64 and if you want to keep the aspect ratio, you need to do any of the following:
a) Crop the image to 128x64.From toolBox(dock in the left hand side most probably), choose Rectangle Select Tool and spcify the size to 128x64 in the bottom of toolbox and select a portion you want and crop it. (menu)Image -> Crop to Selection.
b) Resize the image to less than or equal to 128x64. Then start a new image by (menu)File -> New. Then from the dialog box choose size as 128x64. Copy the previous image to the new image.
c) If you want to just check and image is not matter, image search on Google specifying the size 128x64 ;-)
Step4: Before going to this step, I assume you have an image of the same size of your LCD. In this example, 128x64. Next is the conversion of your color image to monochrome image. For that, choose, (menu)Colors -> Threshold. Using the dialog box, you can change the threshold in realtime.
Step5: Change mode.(menu)Image -> Mode -> Indexed.From the dialog box, choose 'Use Black and White (1bit) palette'. Click 'Convert'
Step6: Save the image.(menu)File -> Save as. Choose extension .bmp (bitmap).

Now your image is ready for embedding to your LCD. For some programs like MikroC for PIC, there is a built in tool to convert the bitmap into array. If you don't have such advanced tools, don't worry, let's do it using open source tools.
Using Octave/Matlab for KS0108
Now you have a monochrome bitmap of only zeros and ones. Now it should be grouped and formatted to a format supported by glcd. I did the conversion using octave. The script shown below accepts the bitmap name as argument and convert it to the glcd compatible form. make appropriate changes to run the script in MATLAB. Also change yourself the program if your lcd size is different.

#This code input a monochrome bitmap of size 128x64 and convert it to a form compatible to ks0108 graphic lcd(glcd)
arg_list=argv();
x=imread(arg_list{1}); #accept argument
num=0;
printf("Controller 1 (left)\n\n");
page=0;
for offset = [1:8:64]
    printf("Page %d:\n",page);
    page+=1;
    for j=1:64
        for i=[offset:offset+7]
            num=num+x(i,j)*(2^(i-offset));
        endfor
        printf("%d ",255-num);
        num=0;
    endfor
    printf("\n\n");
endfor
printf("Controller 2 (right)\n\n");
page=0;
for offset = [1:8:64]
    printf("Page %d:\n",page);
    page+=1;
    for j=65:128
        for i=[offset:offset+7]
            num=num+x(i,j)*(2^(i-offset));
        endfor
        printf("%d ",255-num);
        num=0;
    endfor
    printf("\n\n");
endfor

ChaserDesigner - A professional approach for fancy light design

This project is published in July 2011 th issue of Electronics For You (EFY) magazine (Page no: 94 to 98) titled:"Microcontroller-Based Light Chaser". Thanks to EFY for publishing this. You can read full article from EFYmagonline or purchase one.

ChaserDesigner is a useful project for fancy light designer professionals  as well as enthusiast who want to make their own LED patterns while decorating home during festivals. It's hardware part is simple one which uses 8051(or any variants of 8051) and a handy software part based on Qt. In the GUI, you need to specify how the pattern appear on LEDs(or connected higher loads) and it will automatically generate the source code for 8051(in assembly language). Only you need to do is that, burn the program in to the micro and put it on the circuit. Then the LEDs start to glow in the designed pattern. This is very handy and there are some tools provided to easily make your own patterns. The software works in Linux, Windows, or MAC and hardware components chosen are almost ubiquitous. In case, if any component found unavailable, please comment, I will try to recommend any alternative if any. I have put source code,circuit diagram and all other associated diagrams free for download.

1. contents.zip - Article before published, circuit diagram, images etc.
http://www.4shared.com/file/MolWxWP_/content.html

2. chaserdesigner_src.zip - Software source code.http://www.4shared.com/file/zY9fz6LF/chaserDesigner_src.html


3.chaserdesigner1.0.zip - Windows XP executable file
http://www.4shared.com/file/3WmVxoaF/ChaserDesiner10.html


4.videos.zip - videos describing, how to operate the software and hardware.
http://www.4shared.com/file/EagoltHS/videos.html

Note: Since it is published by EFY,  it is better to read this article in EFY to get more pretty article with PCB layout also.

One day PyBrain came to power....

Recently, I went straight away to PyBrain and found it is useful to AI researchers and enthusiasts. Python rocks once again. PyBrain is a modular library for python. As far as PyBrain developers is concerned, it is Python Based Reinforcement Learning, Artificial Intelligence and Neural Network Library. PyBrain is opensource and it is licensed under BSD software license.
PyBrain simulates neural networks inside our brain in a computer. Once you created the neural networks, you need to train it for a particular task. Sometimes training of more than thousand times is required to properly get done it's job. Sometimes, training will be frustrating especially when you didn't give proper degree of freedom to the neural network structure. However, I found pyBrain interesting.
It is good idea to start with pyBrain documentation. In the beginning of the tutorial, they provide a simple example of training for an X-OR gate. But it will take a lot of training steps to work properly. But for the same neural network structure, if you are trying to simulate an AND gate or an OR gate, you probably get everything done.

Story of a 'spinning lady'

Did you notice the figure above? To see the spinning lady, click this link and return back. Is it a spinning lady? In which direction, you feel the lady is spinning? clockwise or counter-clockwise? One can feel the spinning of the lady in either clockwise or counterclockwise. But once you feel lady spin in one direction, your brain continues in that state and insist to be in that state. If you feel that the lady is spinning in clockwise, it is too difficult to see the motion in counter-clockwise direction. But sometimes our brain switches from one state to other state automatically, but changing the state of feeling of brain is difficult to achieve manually.
This is a beautiful eye illusion. Do you know how that beautiful lady, cheated your brains?
Answer is, the lady didn't cheat you, but the cheater is her shadow. Actually, the image shows the shadow of a spinning lady. In this, a 'shadow' plays in important role in cheating you. The pure shadow of an image will not provide the entire information about an object to the brain. From a shadow, we can't predict whether the front side or backside of the object we are viewing. If you didn't understand what I just said, please go through an example.
Look at the picture below.
The middle picture is photo-shot of the spinning lady. Concentrate on the picture and tell what you are viewing- the frontside or backside? It may be both. Look at the left picture. It is the modified version of middle one by adding eyes in her face. Now you feel that you are viewing the front side of the lady. At the same time, you see the backside of the lady in the right picture, but that also a modified version of middle picture with marking of a hair bud. This is important to be noted. While you are viewing the middle picture only, your brain fall in to the mess of finding whether the shadow is of the front side or backside. Then your brain 'randomly' choose one possibility (not actually). But in other pictures, your brain has powerful proof that indicates the state of the lady's body.
Now the problem associated with the spin direction of the lady is not vague. If your brain 'assumed' a side of the lady's body you are viewing, this will determine which direction, she is spinning.

Make yourself a Qt Hacker

A presentation of Qt for beginners was held in Jyothi Engineering College for ISTE students. It was taken by me and I have just put the presentation and the associated files here and think it may be useful for those people who have attended. For any doubts, feel free to ask me.
Download files here