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<title>The CImg Library - C++ Template Image Processing Toolkit</title>
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<h1>CImg Library Overview</h1><table border="0" cellpadding="0" cellspacing="0">
<tr><td></td></tr>
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The <b>CImg Library</b> is an image processing library, designed for C++ programmers. It provides useful classes and functions to load/save, display and process various types of images.<h2><a class="anchor" name="s1">
Library structure</a></h2>
The CImg Library consists in a <b>single header file</b> CImg.h providing a set of C++ template classes that can be used in your own sources, to load/save, process and display images or list of images. Very portable (Unix/X11,Windows, MacOS X, FreeBSD,..), efficient, simple to use, it's a pleasant toolkit for coding image processing stuffs in C++.<p>
The header file CImg.h contains all the classes and functions that compose the library itself. This is one originality of the CImg Library. This particularly means that :<ul>
<li>No pre-compilation of the library is needed, since the compilation of the CImg functions is done at the same time as the compilation of your own C++ code.</li><li>No complex dependencies have to be handled : Just include the CImg.h file, and you get a working C++ image processing toolkit.</li><li>The compilation is done on the fly : only CImg functionalities really used by your program are compiled and appear in the compiled executable program. This leads to very compact code, without any unused stuffs.</li><li>Class members and functions are inlined, leading to better performance during the program execution.</li></ul>
<p>
The CImg Library is structured as follows :<p>
<ul>
<li>All library classes and functions are defined in the namespace <a class="el" href="namespacecimg__library.html">cimg_library</a>. This namespace encapsulates the library functionalities and avoid any class name collision that could happen with other includes. Generally, one uses this namespace as a default namespace : <div class="fragment"><pre class="fragment"><span class="preprocessor">  #include "CImg.h"</span>
  <span class="keyword">using namespace </span>cimg_library;
  ...
</pre></div></li></ul>
<p>
<ul>
<li>The namespace <a class="el" href="namespacecimg__library_1_1cimg.html">cimg_library::cimg</a> defines a set of <em>low-level</em> functions and variables used by the library. Documented functions in this namespace can be safely used in your own program. But, <b>never</b> use the <a class="el" href="namespacecimg__library_1_1cimg.html">cimg_library::cimg</a> namespace as a default namespace, since it contains functions whose names are already defined in the standard C/C++ library.</li></ul>
<p>
<ul>
<li>The class <a class="el" href="structcimg__library_1_1CImg.html">cimg_library::CImg</a>&lt;T&gt; represents images up to 4-dimensions wide, containing pixels of type <code>T</code> (template parameter). This is actually the main class of the library.</li></ul>
<p>
<ul>
<li>The class <a class="el" href="structcimg__library_1_1CImgList.html">cimg_library::CImgList</a>&lt;T&gt; represents lists of cimg_library::CImg&lt;T&gt; images. It can be used for instance to store different frames of an image sequence.</li></ul>
<p>
<ul>
<li>The class <a class="el" href="structcimg__library_1_1CImgDisplay.html">cimg_library::CImgDisplay</a> is able to display images or image lists into graphical display windows. As you may guess, the code of this class is highly system-dependent but this is transparent for the programmer, as environment variables are automatically set by the CImg library (see also <a class="el" href="group__cimg__environment.html">Setting Environment Variables</a>).</li></ul>
<p>
<ul>
<li>The class <a class="el" href="structcimg__library_1_1CImgException.html">cimg_library::CImgException</a> (and its subclasses) are used by the library to throw exceptions when errors occur. Those exceptions can be catched with a bloc <code>try { ..} catch (CImgException) { .. }</code>. Subclasses define precisely the type of encountered errors.</li></ul>
<p>
Knowing these four classes is <b>enough</b> to get benefit of the CImg Library functionalities.<h2><a class="anchor" name="s2">
CImg version of "Hello world".</a></h2>
Below is a very simple code that creates a "Hello World" image. This shows you basically how a CImg program looks like.<p>
<div class="fragment"><pre class="fragment"><span class="preprocessor">  #include "CImg.h"</span>
  <span class="keyword">using namespace </span>cimg_library;

  <span class="keywordtype">int</span> main() {
    CImg&lt;unsigned char&gt; img(640,400,1,3);        <span class="comment">// Define a 640x400 color image with 8 bits per color component.</span>
    img.fill(0);                                 <span class="comment">// Set pixel values to 0 (color : black)</span>
    <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> purple[] = { 255,0,255 };      <span class="comment">// Define a purple color</span>
    img.draw_text(<span class="stringliteral">"Hello World"</span>,100,100,purple); <span class="comment">// Draw a purple "Hello world" at coordinates (100,100).</span>
    img.display(<span class="stringliteral">"My first CImg code"</span>);           <span class="comment">// Display the image in a display window.</span>
    <span class="keywordflow">return</span> 0;
  }
</pre></div><p>
Which can be also written in a more compact way as :<p>
<div class="fragment"><pre class="fragment"><span class="preprocessor">  #include "CImg.h"</span>
  <span class="keyword">using namespace </span>cimg_library;

  <span class="keywordtype">int</span> main() {
    <span class="keyword">const</span> <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> purple[] = { 255,0,255 };
    CImg&lt;unsigned char&gt;(640,400,1,3,0).draw_text(<span class="stringliteral">"Hello World"</span>,100,100,purple).display(<span class="stringliteral">"My first CImg code"</span>);
    <span class="keywordflow">return</span> 0;
  }
</pre></div><p>
Generally, you can write very small code that performs complex image processing tasks. The CImg Library is very simple to use and provide a lot of interesting algorithms for image manipulation.<h2><a class="anchor" name="s3">
How to compile ?</a></h2>
The CImg library is a very light and user-friendly library : only standard system libraries are used. It avoid to handle complex dependancies and problems with library compatibility. The only thing you need is a (quite modern) C++ compiler :<p>
<ul>
<li><b>Microsoft Visual C++ 6.0, Visual Studio.NET and Visual Express Edition</b> : Use project files and solution files provided in the CImg Library package (directory 'compilation/') to see how it works.</li><li><b>Intel ICL compiler</b> : Use the following command to compile a CImg-based program with ICL : <div class="fragment"><pre class="fragment">  icl /Ox hello_world.cpp user32.lib gdi32.lib
</pre></div></li><li><b>g++ (MingW windows version)</b> : Use the following command to compile a CImg-based program with g++, on Windows : <div class="fragment"><pre class="fragment">  g++ -o hello_word.exe hello_word.cpp -O2 -lgdi32
</pre></div></li><li><b>g++ (Linux version)</b> : Use the following command to compile a CImg-based program with g++, on Linux : <div class="fragment"><pre class="fragment">  g++ -o hello_word.exe hello_world.cpp -O2 -L/usr/X11R6/lib -lm -lpthread -lX11
</pre></div></li><li><b>g++ (Solaris version)</b> : Use the following command to compile a CImg-based program with g++, on Solaris : <div class="fragment"><pre class="fragment">  g++ -o hello_word.exe hello_world.cpp -O2 -lm -lpthread -R/usr/X11R6/lib -lrt -lnsl -lsocket
</pre></div></li><li><b>g++ (Mac OS X version)</b> : Use the following command to compile a CImg-based program with g++, on Mac OS X : <div class="fragment"><pre class="fragment">  g++ -o hello_word.exe hello_world.cpp -O2 -lm -lpthread -L/usr/X11R6/lib -lm -lpthread -lX11
</pre></div></li><li><b>Dev-Cpp</b> : Use the project file provided in the CImg library package to see how it works.</li></ul>
<p>
If you are using another compilers and encounter problems, please <a href="http://www.greyc.ensicaen.fr/~dtschump">write me</a> since maintaining compatibility is one of the priority of the CImg Library. Nevertheless, old compilers that does not respect the C++ norm will not support the CImg Library.<h2><a class="anchor" name="s4">
What's next ?</a></h2>
If you are ready to get more, and to start writing more serious programs with CImg, you are invited to go to the <a class="el" href="group__cimg__tutorial.html">Tutorial : Getting Started.</a> section. </div>
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