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<title>Lua Binding</title>
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<h2>Lua Binding</h2>
<h3><a name="Overview">Overview</a></h3>
<p><strong>I</strong><span lang="en-us"><strong>m</strong></span><strong>Lua</strong> was developed to make all functionalities of the
<strong>IM</strong> library available to Lua programmers. To use the <strong>I</strong><span lang="en-us"><strong>m</strong></span><strong>Lua</strong>
bindings, your executable must be linked with the "imlua" library, and you must call the initialization function
<strong><font face="Courier New">imlua_open</font></strong> declared in the header file <strong>
<font face="Courier New">imlua</font><font size="2" face="Courier New">.</font><font face="Courier New">h</font></strong>,
as seen in the example below:</p>
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<p align="center">in Lua<span lang="en-us"> </span>5</th>
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<pre>#include <lua.h>
#include <lualib.h>
#include <lauxlib.h>
<b><font color="#FF0000">#include <imlua.h></font></b></pre>
<pre>void main(void)
{
lua_State *L = lua_open();
luaopen_string(L);
luaopen_math(L);
luaopen_io(L);
<b> <font color="#FF0000">imlua_open(L);</font>
</b>
lua_dofile("myprog.lua");
lua_close(L);
}</pre>
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<p>The <strong>imlua_open</strong> function registers all <strong>IM</strong> functions and constants
your Lua program will need. The use of the <strong>I</strong><span lang="en-us"><strong>m</strong></span><strong>Lua</strong> functions in Lua is generally identical to their equivalents in C.
Nevertheless, there are several exceptions due to differences between the two languages. Notice that, as opposed to C,
in which the flags are<i> </i>combined with the bitwise operator OR, in Lua the flags are added arithmetically. </p>
<p>The other secondary libraries also have their initialization functions declared in
<strong>imlua.h</strong>
and each one have a separate library to be linked with the application. See <a href="doxygen/group__imlua.html">IM Lua
5 Binding</a> reference.</p>
<p>The I<span lang="en-us">m</span>Lua dynamic libraries are also compatible with the Lua 5 "loadlib" function.<span lang="en-us">
</span>Here is an example on how to dynamically load I<span lang="en-us">M</span>
in Lua 5<span lang="en-us">.1</span>:</p>
<pre>local i<span lang="en-us">m</span>lua_open = package.loadlib("i<span lang="en-us">m</span>lua51.dll", "i<span lang="en-us">m</span>lua_open")
i<span lang="en-us">m</span>lua_open()</pre>
<p><strong>Lua</strong> 5.1 "require" can be used for all the <strong>
ImLua</strong>
libraries. You can use <b>require</b>"<strong>im</strong><b>lua</b>" and so on, but the LUA_CPATH
must also contains the following: </p>
<pre>"./lib?51.so;" [in UNIX]
".\\?51.dll;" [in Windows]</pre>
<p>The <a href="http://luabinaries.luaforge.net/">LuaBinaries</a> distribution already includes these modifications on the
default search path.</p>
<p>The simplest form <b>require</b>"<b>i<span lang="en-us">m</span></b>"
and so on, can not be used because there are IM dynamic libraries with names
that will conflict with the names used by <b>require</b> during search.</p>
<h3><a name="New Functions">Function Names and Definitions</a></h3>
<p>In Lua, because of the name space "im" all the functions and definitions have their names prefix changed. The
general rule is quite simple:</p>
<pre>imXxx -> im.Xxx
IM_XXX -> im.XXX
imFileXXX(ifile,... -> ifile:XXX(...
imImageXXX(image,... -> image:XXX(...</pre>
<h3>Modifications to the API</h3>
<p>New functions (without equivalents in C) were implemented to create and
destroy objects that do not exist in C. For instance functions were developed
to create and destroy images, files, viceo capture and palette. All the
metatables have the "tostring" method implemented to help debuging.</p>
<p>Some functions were modified to receive those objects as parameters.</p>
<p>Also the functions which receive values by reference in C were modified. Generally, the values of
parameters that would have their values modified are now returned by the function in the same order.</p>
<p>In C there is no parameter checking in the processing functions, but in Lua
all parameters are checked and a Lua error is emitted when check fails.</p>
<h3>Garbage Collection</h3>
<p>All the objects are garbage collected by the Lua garbage collector.</p>
<h3><a name="Integration with IMLua">Integration with CDLua</a></h3>
<p>In <b>CDLua</b> there is an additional library providing simple functions to map the
<strong>imImage</strong>
structure to the <strong>cdBitmap</strong> structure. And some facilities to
draw an image in a CD canvas. See also the <a target="_blank" href="http://www.tecgraf.puc-rio.br/cd">CD documentation</a> and
the <a href="doxygen/group__imlua.html">IM Lua 5 Binding</a> reference.</p>
<p>Color values and palettes can be created and used transparently in both libraries. Palettes and color values are
100% compatible between CD and IM.</p>
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