Script for downloading LFPW

Today I needed to download (thus parse) the Labeled Face Parts in the Wild (LFPW). Although it seems an straight forward task, as the datasets have the urls, many of them are dead/broken or pointing to something else.

I thought it will take me a couple of minutes to put an script an have everything running smoothly. However, I found that the urls sometimes download html files, or garbage gifs. So I need to analyze the output and then choose some files and discard the others. And because I don’t want to do it manually, I put a script to achieve it.

My solution is in awk, probably it may be easier in pearl or python but I started with awk and stick with it.

To run it, you should be in the directory in which you want the images to end up.

awk '/average/ {
  result = ""
  download = ""
  name = ""
  cmd = "wget -t 1 -nv " $1 " 2>&1"
  while ( (cmd | getline line) > 0 )
    result = result " " line
  close(cmd)
  print "res: " result > "/dev/stderr"
  if (result != "" && match(result,/ERROR/) == 0) {
    match(result,/".+"/);
    downloaded = substr(result,RSTART+1,RLENGTH-2)
    print "file: " downloaded > "/dev/stderr"
    if (match(downloaded,/\.(htm|php|gif)/) != 0) {
      print "deleting: " downloaded > "/dev/stderr"
      system("rm \"" downloaded "\"")
    } else {
      if( match(tolower(downloaded),/\.(jpg|jpeg|bmp|png)$/) == 0 ) {
        if( match(tolower(downloaded),/\.(jpg|jpeg|bmp|png)/) != 0 )
          downloaded_fix = substr(downloaded,1,RSTART) substr(downloaded,RSTART+RLENGTH+1,length(downloaded))
        else
          downloaded_fix = downloaded
        name = downloaded_fix ".jpg"
        print "adding ext: " downloaded_fix > "/dev/stderr"
        system("mv \"" downloaded "\" \"" name "\"")
      } else
        name=downloaded
      print "writting: " name > "/dev/stderr"
      print name, $0
    }
  } else
    print "skipping: " name > "/dev/stderr"
  print "\n" > "/dev/stderr"
}' ../kbvt_lfpw_v1_train.csv > ../fixed_train.txt 2> ../train.log

Some comments about the code:

• I’m processing only the “average” worker, and ignoring all the other (3) entries.
• I choose to change the extension of the files that download without one to jpg (you may change it to something else if needed—line 23).
• Also I’m deleting all the htm(l), php, and gifs that may be downloaded (line 14).
• I’m checking the extensions directly, as the files that download have really random names (and I’m mean it: 86f6ec6e-9de5-11de-805f-588d52b6bd80, how is that an image name?… moving on), but you may add another ones if needed (I didn’t check thoroughly)—line 18.
• When a downloaded file name already exist wget adds a suffix .# to the file. Thus, I’m stripping the possible extensions from each file, if it doesn’t end with a valid extension but contains such extension (line 20).
• All the log messages (print ... > "/dev/stderr") are redirected to the standard error. That’s why at the end you get them with “2> ../<yourfile>” (line 28).
• And to get the new list of files that were downloaded you redirect the standard output to your file by “> ../<fixed-file>” (line 34).

I haven’t checked all the files, but that is the first version. Any improvements are welcomed.

Using TikZ Chains Library with labeled edges extension

The other day I need to create a diagram, and went in the TikZ way. I was using the chains library to produce the diagram. But I face some problems, I needed to add labels to the edges created by the chain. However, this is not supported natively by the library.

I found a cool code that exemplifies how to add the edges to the chain, but it removes the old notation

\chainin (node) [join=with srcNode by style]

and make you use a new definition. However, I still need to use the styles and the source node notation. So, I start digging in the chains library code and modify it to allow the use of the label notation from other examples. The fix is

\makeatletter
\def\tikz@lib@parse@join#1{%
  \def\tikz@temp{#1}%
  \ifx\tikz@temp\pgfutil@empty%
    \tikz@lib@parse@join@by by \pgf@stop%
  \else%
    \pgfutil@in@{with }{#1}%
    \ifpgfutil@in@% 'with [by] [label]'
      \pgfutil@in@{by }{#1}%
      \ifpgfutil@in@% 'with by [label]'
        \pgfutil@in@{label }{#1}%
        \ifpgfutil@in@% 'with by label'
          \tikz@lib@parse@join@with@by@label#1\pgf@stop%
        \else% 'with by'
          \tikz@lib@parse@join@with@by#1\pgf@stop%
        \fi%
      \else% 'with [label]'
        \pgfutil@in@{label }{#1}%
        \ifpgfutil@in@% 'with label'
          \tikz@lib@parse@join@with@label#1\pgf@stop%
        \else% with
          \tikz@lib@parse@join@with@by#1 by \pgf@stop%
        \fi%
      \fi%
    \else% '[by] [label]'
      \pgfutil@in@{by }{#1}%
      \ifpgfutil@in@% 'by [label]'
        \pgfutil@in@{label }{#1}%
        \ifpgfutil@in@% 'by label'
          \tikz@lib@parse@join@by@label#1\pgf@stop%
        \else% 'by'
          \tikz@lib@parse@join@by#1\pgf@stop%
        \fi%
      \else% '[label]'
        \pgfutil@in@{label }{#1}%
        \ifpgfutil@in@% 'label'
          \tikz@lib@parse@join@label#1\pgf@stop%
        \else%
          \tikz@lib@parse@join@by#1 by \pgf@stop%
        \fi%
      \fi%
    \fi%
  \fi%
}
\def\tikz@lib@parse@join@with@by@label with #1 by #2 label #3\pgf@stop{%
  \tikzset{after node path={(#1)edge[every join,#2]#3(\tikzchaincurrent)}}%
}
\def\tikz@lib@parse@join@with@label with #1 label #2\pgf@stop{%
  \tikzset{after node path={(#1)edge[every join]#2(\tikzchaincurrent)}}%
}
\def\tikz@lib@parse@join@by@label by #1 label #2\pgf@stop{%
  \tikzset{after node path={\ifx\tikzchainprevious\pgfutil@empty\else(\tikzchainprevious)edge[every join,#1]#2(\tikzchaincurrent)\fi}}%
}
\def\tikz@lib@parse@join@label label #1\pgf@stop{%
  \tikzset{after node path={\ifx\tikzchainprevious\pgfutil@empty\else(\tikzchainprevious)edge[every join]#1(\tikzchaincurrent)\fi}}%
}
\makeatother

This allows one to use the chains like:

\chainin (node) [join=with anotherNode by myStyle label {node[above] {some Tag}}];
\chainin (node) [join=by myStyle label {node[above] {some Tag}}];

Note that the order needs to be maintained, so you can use [with] [label] [tag] and omit any of those, while the order is maintained. A minimal working example is below:

\documentclass{standalone}

\usepackage{tikz}
\usetikzlibrary{shapes,% for the rectangle
                chains,% provides the chains
                scopes}% allows to replace \begin{scope} \end{scope} with {}

\makeatletter
\def\tikz@lib@parse@join#1{%
  \def\tikz@temp{#1}%
  \ifx\tikz@temp\pgfutil@empty%
    \tikz@lib@parse@join@by by \pgf@stop%
  \else%
    \pgfutil@in@{with }{#1}%
    \ifpgfutil@in@% 'with [by] [label]'
      \pgfutil@in@{by }{#1}%
      \ifpgfutil@in@% 'with by [label]'
        \pgfutil@in@{label }{#1}%
        \ifpgfutil@in@% 'with by label'
          \tikz@lib@parse@join@with@by@label#1\pgf@stop%
        \else% 'with by'
          \tikz@lib@parse@join@with@by#1\pgf@stop%
        \fi%
      \else% 'with [label]'
        \pgfutil@in@{label }{#1}%
        \ifpgfutil@in@% 'with label'
          \tikz@lib@parse@join@with@label#1\pgf@stop%
        \else% with
          \tikz@lib@parse@join@with@by#1 by \pgf@stop%
        \fi%
      \fi%
    \else% '[by] [label]'
      \pgfutil@in@{by }{#1}%
      \ifpgfutil@in@% 'by [label]'
        \pgfutil@in@{label }{#1}%
        \ifpgfutil@in@% 'by label'
          \tikz@lib@parse@join@by@label#1\pgf@stop%
        \else% 'by'
          \tikz@lib@parse@join@by#1\pgf@stop%
        \fi%
      \else% '[label]'
        \pgfutil@in@{label }{#1}%
        \ifpgfutil@in@% 'label'
          \tikz@lib@parse@join@label#1\pgf@stop%
        \else%
          \tikz@lib@parse@join@by#1 by \pgf@stop%
        \fi%
      \fi%
    \fi%
  \fi%
}
\def\tikz@lib@parse@join@with@by@label with #1 by #2 label #3\pgf@stop{%
  \tikzset{after node path={(#1)edge[every join,#2]#3(\tikzchaincurrent)}}%
}
\def\tikz@lib@parse@join@with@label with #1 label #2\pgf@stop{%
  \tikzset{after node path={(#1)edge[every join]#2(\tikzchaincurrent)}}%
}
\def\tikz@lib@parse@join@by@label by #1 label #2\pgf@stop{%
  \tikzset{after node path={\ifx\tikzchainprevious\pgfutil@empty\else(\tikzchainprevious)edge[every join,#1]#2(\tikzchaincurrent)\fi}}%
}
\def\tikz@lib@parse@join@label label #1\pgf@stop{%
  \tikzset{after node path={\ifx\tikzchainprevious\pgfutil@empty\else(\tikzchainprevious)edge[every join]#1(\tikzchaincurrent)\fi}}%
}
\makeatother

\begin{document}
\begin{tikzpicture}[
  nonterminal/.style={
    rectangle,
    minimum size=6mm,
    very thick,
    draw=red!50!black!50,
    top color=white, % a shading that is white at the top...
    bottom color=red!50!black!20, % and something else at the bottom
    font=\itshape
  },
  terminal/.style={
    rectangle,minimum size=6mm,rounded corners=3mm,
    very thick,draw=black!50,
    top color=white,bottom color=black!20,
    font=\ttfamily
  },
  every on chain/.style={join}, every join/.style={->}
]

\matrix[column sep=4mm] {
  % First row:
  & & & & \node (plus) [terminal] {+};&\\
  % Second row:
  \node (ui1)   [nonterminal] {unsigned integer};&
  \node (dot)   [terminal]    {.};               &
  \node (digit) [terminal]    {digit};           &
  \node (e)     [terminal]    {E};               &
  & % space in between
  \node (ui2) [nonterminal] {unsigned integer};\\
  % Third row:
  & & & & \node (minus)[terminal] {-};&\\
  };

{ [start chain]
  \chainin (ui1);
  \chainin (dot);
  \chainin (digit);
  \chainin (e);
  { [start branch=plus]
    \chainin (plus) [join=label {node[above left]{a label}}];
  }
  { [start branch=minus]
    \chainin (minus);
  }
  \chainin (ui2) [join=with chain/plus-end label {node[above right] {plus label}}, join=with chain/minus-end by dashed label {node [below right]{minus label}}];
}
\end{tikzpicture}
\end{document}

HTH…

PS. This post was inspired by this TeX.SX question, and I put this answer also there. You can found more about (La)TeX there.

MATLAB to PSTricks

So, I’ve been trying to include more good looking figures into . I came across an script to convert from MATLAB to pstricks. However, it looks like it is not maintained anymore.

However, I made some little changes and fix a bug that I found. So, I want to put it here for anyone who is interested in use it.

The changes from the original:

• The standalone file generation uses the standalone package, so (in theory) can compile faster. Because, for some strange reason, when I include these files into any document it takes forever to compile.
• Now, the script can set any option from the options data structure (see the file to understand what I’m saying) individually, instead of passing the whole thing.
• I fix a bug for data points outside of the axes not appearing.

The script is really good, although it has some limitations. Still, I will try to keep this entry up to date if I made some changes to the file.

So the script is here: fig2texps. To use the script easily call

h = figure; % a handle for the figure
plot(...);  % your figure here
fig2texps(h,'file.tex'); % basic invocation

To check all the options you can set see the globals struct in line 187.

Hope that helps…

Updates:

(07.11.11) I found one bug, if the legend is outside of the figure the labels were place improperly. I hope it is fixed now.

(16.11.11) Fix bug when lines are out of the axis box. If two points were above or below the axis a line was drawn. Now, it is not.

Decimal alignment in LaTex tables

So, I always look for this when I need it. However, I always keep forgetting it. So I decide to put it here for a little reminder.

Have you tried to align decimal in LaTex before? Did you do like this:

\begin{tabular}{r@{.}l}
  Heading\\
  3&14159\\
  16&2\\
  123&456\\
\end{tabular}

Have you try to type a lot of numbers using this notation? Painful, isn’t it? Is there an easier way?, you may ask. Yes there is, dcolumn to the rescue! The package dcolumn can save you a lot of typing time. The way to use it is really simple.

\usepackage{dcolumn}
\begin{tabular}{D{.}{.}{3.5}}
  \multicolumn{1}{c}{Heading}\\
  3&14159\\
  16&2\\
  123&456\\
\end{tabular}

Notice that in this example you need to use \multicolumn in the heading of that column. Nevertheless, dcolumn has a big notation, but you can replace it by a new definition using the \newcolumntype command. Then you would have something like this:

\usepackage{dcolumn}
\newcolumntype{d}[1]{D{.}{.}{#1}}
\begin{tabular}{d{3.5}}
  \multicolumn{1}{c}{Heading}\\
  3&14159\\
  16&2\\
  123&456\\
\end{tabular}

Hope this helps!

Remove white space from figures in MATLAB

Today I was struggling again with those annoying white spaces around the figures in MATLAB when you convert the figure to EPS, TIFF, PNG, JPEG or any other format. After some time, I discover the LooseInset property. This command will remove the white spaces and tight  the image borders.

set(gca,'LooseInset',get(gca,'TightInset'))

So, this will make the process of creating EPS figures in MATLAB easier. Sadly, it only work for square figures.

Hope that helps.

Compiling Poppler on Windows

I’ve been struggling trying to install Poppler under Windows, and there is no much information out there. And the few people who claim that works on Windows don’t say how they did it.

Thus, today I will try to guide you on how to make Poppler works on Windows with QT. The goal of this tutorial is to compile the poppler_qt4viewer demo.

The things you will need

Ok, let’s begin the journey. Before starting you need to download some libraries

• QT (4.7.4 source: zip, tar.gz)
• freetype
• cairo
• zlib
• Openjpeg

You will need QT, at the time I’m writing the latest version is 4.7.4 (source zip, tar.gz). I will recommend you to download the source because it gave me some problems when I downloaded the binaries. Then you need the freetype, cairo, and zlib. However, those are not that easy to find in Windows. So, you can download them from any site that maintains a build like GTK+ or Inkscape. I got mine from the GTK+ site and used the developer version of them. You can use, however, the version of your choice. And finally the other library we need is openjpeg, and you can download the source code and build it from there.

Now that you have the libraries, you will need the tools to build them. So go and set Visual Studio or a compiler for Windows, and you will also need CMake.

Building QT

Before getting into Poppler or other libraries, you will need to build QT. I prefer to build it instead of downloading the binaries, because the compiled version didn’t work for me 😦 . There is a detail instruction set in here. So I will give you the short story.

1. First unzip the sources into your hard drive, for here on I will call this path $QT_PATH=c:\QT.
2. Then you need to add the path to the environment variables. Go to My Computer Properties, in the Advanced Tab search for the Environment Variables. Then add to the PATH variable the path to the bin folder of your extracted QT files ($QT_PATH\bin).
3. Now open a console from Visual Studio, and then go to the $QT_PATH and execute configure and then nmake.

   cd $QT_PATH
   configure
   nmake
   

   If you have any problem in this part check the installation page.

Preparing the environment

After you get all the libraries (cairo, freetype, zlib, and openjpeg) you need to unzip them into a folder, I will call it $TOOLS from here on.

Then, for example, you will have $TOOLS\cairo-dev_1.10.2-1_win32 if you choose the development version of cairo library. And all the other libraries can be in this folder too. We will use them later when compiling Poppler. In my case I used the dev versions of all the libraries, and in order to make it easier I will refer to them as follows

• $CAIRO = $TOOLS\cairo-dev_1.10.2-1_win32
• $FREETYPE = $TOOLS\freetype-dev_2.4.2-1_win32
• $ZLIB = $TOOLS\zlib-dev_1.2.5-2_win32
• $OPENJPEG = $TOOLS\openjpeg_v1_4_sources_r697

Building Openjpeg

Now we will build Openjpeg using CMake. Open CMake GUI and in the source path choose $OPENJPEG path; for the build binaries you need to create a folder, mine is $OPENJPEG\build. Then you just need to press Configure; select your version of Visual Studio and wait for it to end, and then just press it again. It should be no more red rows in the output. If there are, try to solve the problems it mention. After that press Generate and the project should be in $OPENJPEG\build or wherever you put it.

Then open ALL_BUILD project and compile it. The binaries will be in $OPENJPEG\build\bin.

Building Poppler Library

Note: Different target names for Debug and Release.
In case you need to give a postfix to the debug and release libraries, e.g., popplerd.lib for debug and poppler.lib for release, you need to add this line to the CMakeList (after the set(CMAKE_MODULE_PATH ... ) is OK)

set(CMAKE_DEBUG_POSTFIX d)

Just change the d for the postfix you want to use, maybe _d.

Now that we have all the prerequisites we are ready to build Poppler. Put the sources in a folder, I will call it $POPPLER, and create a folder for the build like in the openjpeg step, mine it is in $POPPLER\build.

Now open CMake, and point the source-path to $POPPLER and the build-path to $POPPLER\build, and press Configure. Again, select the Visual Studio of your choice and then wait for it to configure. An error message will appear regarding the freetype library, don’t worry we are expecting it. You will see a lot of red rows in the output. Look for FREETYPE_INCLUDE_DIR_freetype2, FREETYPE_INCLUDE_DIR_ft2build, FREETYPE_LIBRARY and point them to:

• FREETYPE_INCLUDE_DIR_freetype2: $FREETYPE\include\freetype2
• FREETYPE_INCLUDE_DIR_ft2build: $FREETYPE\include
• FREETYPE_LIBRARY:$FREETYPE\lib\freetype.lib

Then hit Configure again and wait. An error will occur again, and we will need to set the cairo and zlib libraries. Look for the next variables and set them accordingly

• CAIRO_INCLUDE_DIR: $CAIRO\include
• CAIRO_LIBRARY: $CAIRO\lib\cairo.lib
• LIBOPENJPEG_INCLUDE_DIR: $OPENJPEG\libopenjpeg
• LIBOPENJPEG_LIBRARIES: $OPENJPEG\bulid\bin\Release\openjpeg.lib (this can be Release or Debug depends on you)

Also, you need to change the zlib variables. If you don’t see them, mark the Advance option.

• ZLIB_INCLUDE_DIR: $ZLIB\include
• ZLIB_LIBRARY: $ZLIB\lib\zdll.lib

Take special attention to this variables if you have a LaTex related system in you computer because it will look for that binaries. However, if the include libraries are not there Poppler won’t compile.

After you change those variables, you need to disable the options WITH_Iconv, WITH_PNG, and WITH_GLIB. And then press Configure again, check for no red rows and then press Generate. Go to $POPPLER\build and execute ALL_BUILD, compile and that should be it for the Poppler library.

Executing the Demo

If you want to execute the demo, and you didn’t add everything to your path you will need some libraries in order to run it. The demo will be located at $POPPLER\build\qt4\demos\Debug or Release accordingly to your compiling settings. You will need the following libraries

• poppler-qt4.dll: $POPPLER\build\qt4\src\Debug
• openjpeg.dll: $OPENJPEG\build\bin\Debug
• QtCored4.dll, QtGuid4.dll, QtTestd4.dll, QtXmld4.dll: $QT_PATH\lib (the ‘d’ is needed if you are working with Debug version, if it is Release version loose it)

If you want to port your demo, you will need to add the msvcpX.dll and msvcrX.dll where X is the number of your compiler (also the debug version of those libraries, the ones that includes the ‘d’), you can find those libraries in your system.

Fonts problems?

I encounter some problems with the demo. The application started, it open the PDFs but no fonts appeared. After struggling a little bit I found that I need the freetype6.dll, I found that library in my installation of Inkscape. However, I’m not sure why the Debug version doesn’t ask for the library. Nevertheless, if you put that library in your Release version the fonts start appearing.

Concluding…

Up to here I was able to build the Poppler library and run the demo inside. I will explore further to see the capabilities of the library and how can I incorporate it into my projects. I hope this help you, so you won’t waste your time trying to do things that, now that I know how to do them, look easy but are not when there is not enough documentation around.

It is hard at the beginning but if you struggle long enough it becomes easier. 

Wine version mismatch error

I just update wine while running a couple of programs, and suddenly this error appeared:

wine client error:0: version mismatch <version1>/<version2>.
Your wineserver binary was not upgraded correctly,
or you have an older one somewhere in your PATH.
Or maybe the wrong wineserver is still running?

It seams that wine is complaining because the binaries that are currently running does not match with the new ones installed. So, you can have only one version of wineserver running at the same time. To solve the problem you just need to kill the old wine and that’s it. You can achieve this using this commands

pkill wine
pkill exe

You can check that the process is really dead with

pstree

Hope that helps if you get the same error

1D Histogram on OpenCV

I started working on OpenCV this week, and it had been quite a journey.

I started with some easy programs. However, there is a new (at least for me is new) version of OpenCV with wrappers for C++. Therefore, the examples in the web, most of the time, do not work as they are.

So, today I will show you some of the work I’ve done deciphering the examples that work with the C code for the new wrappers.

OK, lets see. I wanted to do a simple histogram visualization of an image. But, all the examples in the web deal with two dimensional histograms, or with the old syntax. After checking a couple of webs I came up with a solution inspired by this post.

The idea is the same, but I change the functionality to work with OpenCV v2.2.

First, you need to create the histogram options, I think is really annoying, but it gives you more control over your final histogram.

  int nbins = 256; // lets hold 256 levels
  int hsize[] = { nbins }; // just one dimension
  float range[] = { 0, 255 };
  const float *ranges[] = { range };
  int chnls[] = {0};

with this code, you create only one dimensional histogram with 256 bins in the range of 0 to 255, and you specify to work with the channel 0 (the only channel). If you need more dimensions just add them in the hsize and ranges variables. If you see further, the histogram computation is designed to work with several dimensions, that’s why we need to pass arrays to it.

Then you just need to compute the histogram using

<pre>  calcHist(&colors[0], 1, chnls, Mat(), hist,1,hsize,ranges);</pre>

Note that the histogram image hist must be a MatND or a SparceMat. Then to render the histogram just compute the rectangles for each bin using the fillConvexPoly function. The full code looks like this. You can download the files here, please change the extension to rar to use them. It contains a CMakeLists to build it using CMake.

HTH :mrgreen:, I hope to be posting more on this topics soon.

#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include <iostream>

using namespace cv;
using namespace std;

Mat imHist(Mat hist, float scaleX=1, float scaleY=1){
  double maxVal=0;
  minMaxLoc(hist, 0, &maxVal, 0, 0);
  int rows = 64; //default height size
  int cols = hist.rows; //get the width size from the histogram
  Mat histImg = Mat::zeros(rows*scaleX, cols*scaleY, CV_8UC3);
  //for each bin
  for(int i=0;i<cols-1;i++) {
    float histValue = hist.at<float>(i,0);
    float nextValue = hist.at<float>(i+1,0);
    Point pt1 = Point(i*scaleX, rows*scaleY);
    Point pt2 = Point(i*scaleX+scaleX, rows*scaleY);
    Point pt3 = Point(i*scaleX+scaleX, (rows-nextValue*rows/maxVal)*scaleY);
    Point pt4 = Point(i*scaleX, (rows-nextValue*rows/maxVal)*scaleY);

    int numPts = 5;
    Point pts[] = {pt1, pt2, pt3, pt4, pt1};

    fillConvexPoly(histImg, pts, numPts, Scalar(255,255,255));
  }
  return histImg;
}

int main( int argc, char** argv ) {
  // check for supplied argument
  if( argc < 2 ) {
    cout << "Usage: loadimg <filename>\n" << endl;
    return 1;
  }

  // load the image, load the image in grayscale
  Mat img = imread( argv[1], CV_LOAD_IMAGE_COLOR );

  // always check
  if( img.data == NULL ) {
    cout << "Cannot load file " << argv[1] << endl;
    return 1;
  }

  //Hold the histogram
  MatND hist;
  Mat histImg;
  int nbins = 256; // lets hold 256 levels
  int hsize[] = { nbins }; // just one dimension
  float range[] = { 0, 255 };
  const float *ranges[] = { range };
  int chnls[] = {0};

  // create colors channels
  vector<Mat> colors;
  split(img, colors);

  // compute for all colors
  calcHist(&colors[0], 1, chnls, Mat(), hist,1,hsize,ranges);
  histImg = imHist(hist,3,3);
  imshow("Blue",histImg);

  calcHist(&colors[1], 1, chnls, Mat(), hist,1,hsize,ranges);
  histImg = imHist(hist,3,3);
  imshow("Green",histImg);

  calcHist(&colors[2], 1, chnls, Mat(), hist,1,hsize,ranges);
  histImg = imHist(hist,3,3);
  imshow("Red",histImg);

  // show image
  imshow("Image", img);

  // wait until user press a key
  waitKey(0);

  // no need to release the memory, Mat do it for you
  return 0;
}

Missing Effects Menu Inkscape

I was trying to do an interpolate operation, and for my surprise there is no “Effects” menu, as the tutorial (ver. 0.48) and the Inkscape  page state.

However, after looking around for a while I found the “Interpolate” effect in other place.

Go to Extensions -> Generate from Path -> Interpolate

I didn’t use the “Effects” menu before, so I don’t know if all of them are moved to the “Extensions” menu. However, now you know where to start looking for.

Align number by decimals in tables

Before finding siunitx, to align decimals I have to use the odd format r@{.}l to align decimals. This isn’t just odd, but it requires a lot of work if you have a lot of data.

Today, I just found about siunitx and I’m in love with it. I’s so easy to align the decimals, but also provides other powerful macros to manipulate numbers and units.

A simple examle for its use

\usepackage{siunitx}
\begin{document}
\begin{tabular}{S[table-format=3.2]}
{Numbers}\\ \hline
555 \\
7.77 \\
99.9
\end{tabular}

where S is a type of column that will align the numbers by the point, the text in the columns should be between braces {}, and lastly you can specify the width of the column by using the table-format, there you say the number of integers and then the number of decimals.
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