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<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Dealing with the visibility maps (the seams)</title><meta name="generator" content="DocBook XSL Stylesheets V1.79.1"><link rel="home" href="index.html" title="The Liquid Rescale library Manual"><link rel="up" href="api-manual.html" title="Chapter 2. LqR library API user manual"><link rel="prev" href="tuning.html" title="Tuning"><link rel="next" href="attach-images.html" title="Attaching extra images"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Dealing with the visibility maps (the seams)</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="tuning.html">Prev</a> </td><th width="60%" align="center">Chapter 2. LqR library API user manual</th><td width="20%" align="right"> <a accesskey="n" href="attach-images.html">Next</a></td></tr></table><hr></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="vmaps"></a>Dealing with the visibility maps (the seams)</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="vmaps.html#vmap-dump">Dumping the visibility map</a></span></dt><dt><span class="sect2"><a href="vmaps.html#activate-dump">Storing the visibility maps</a></span></dt><dt><span class="sect2"><a href="vmaps.html#access-vmap">Accessing the internally attached visibility maps</a></span></dt><dt><span class="sect2"><a href="vmaps.html#vmaps-objs">The visibility map objects</a></span></dt><dt><span class="sect2"><a href="vmaps.html#import-vmap">Importing a visibility map in a carver</a></span></dt><dt><span class="sect2"><a href="vmaps.html#save-load-vmaps">Saving and loading visibility maps to/from files</a></span></dt></dl></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="vmap-dump"></a>Dumping the visibility map</h3></div></div></div><p> The visibility map can be saved at any moment by calling the function: </p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">LqrVMap* <b class="fsfunc">lqr_vmap_dump</b>(</code></td><td>LqrCarver* <var class="pdparam">carver</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><p> </p><p> This function will return a pointer to a newly allocated <code class="classname">LqrVMap</code> object, or <code class="literal"><span class="returnvalue">NULL</span></code> in case of failure. See also the section "<a class="link" href="vmaps.html#vmaps-objs" title="The visibility map objects">The visibility map objects</a>". </p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="activate-dump"></a>Storing the visibility maps</h3></div></div></div><p> By default, the computed visibility maps are wasted. Instead of saving them individually, it is possible to automatically dump them at the end of the carving process, attaching them to their associated <code class="classname">LqrCarver</code>. In order to activate this feature, the following function has to be called: </p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">lqr_carver_set_dump_vmaps</b>(</code></td><td>LqrCarver* <var class="pdparam">carver</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><p> </p><p> This will have the effect of dumping the visibility map each time <code class="function">lqr_carver_resize</code> is invoked, and storing it internally. When resizing along both directions, two maps will be dumped, one for each direction. </p><p> In order to revert the effect of <code class="function">lqr_carver_set_dump_vmaps</code>, thus stopping the automatic dumping, use the function </p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">lqr_carver_set_no_dump_vmaps</b>(</code></td><td>LqrCarver* <var class="pdparam">carver</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><p> </p><p> Alternatively, the internal storage mechanism can be called over the current visibility map at any given moment by calling this function: </p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">LqrRetVal <b class="fsfunc">lqr_vmap_internal_dump</b>(</code></td><td>LqrCarver* <var class="pdparam">carver</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><p> </p><p> The dumped maps are stored inside <code class="classname">LqrVMap</code> objects, and these are attached to their corresponing <code class="classname">LqrCarver</code> object through a linked list, whose type is <code class="classname">LqrVMapList</code> </p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="access-vmap"></a>Accessing the internally attached visibility maps</h3></div></div></div><p> To access the maps attached to a carver one has first to obtain the pointer to the list, with the function: </p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">LqrVMapList* <b class="fsfunc">lqr_vmap_list_start</b>(</code></td><td>LqrCarver* <var class="pdparam">carver</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><p> </p><p> Then, one can iterate through the attached maps by using these two functions: </p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">LqrVMap* <b class="fsfunc">lqr_vmap_list_current</b>(</code></td><td>LqrVMapList* <var class="pdparam">list</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><p> </p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">LqrVMapList* <b class="fsfunc">lqr_vmap_list_next</b>(</code></td><td>LqrVMapList* <var class="pdparam">list</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><p> </p><p> Here is a sample code usage: </p><div class="example"><a name="ex-vmaplist1"></a><p class="title"><b>Example 2.7. Accessing visibility maps #1</b></p><div class="example-contents"><pre class="programlisting"> LqrVMap *vmap; LqrVMapList *list; list = lqr_vmap_list_start (carver); while (list) { vmap = lqr_vmap_list_current (list); /* ... do something on vmap ... */ list = lqr_vmap_list_next (list); } </pre></div></div><p><br class="example-break"> </p><p> The maps will always be accessed in the order in which they were dumped. </p><p> Alternatively, one can apply a function to all the elements of the list, through this function: </p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">LqrRetVal <b class="fsfunc">lqr_vmap_list_foreach</b>(</code></td><td>LqrVMapList* <var class="pdparam">list</var>, </td></tr><tr><td> </td><td>LqrVMapFunc <var class="pdparam">func</var>, </td></tr><tr><td> </td><td>gpointer <var class="pdparam">data</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><p> </p><p> To use this second method, you'll need to define a function first, as in this sample code: </p><div class="example"><a name="ex-vmaplist2"></a><p class="title"><b>Example 2.8. Accessing visibility maps #2</b></p><div class="example-contents"><pre class="programlisting"> LqrRetVal my_func (LqrVMap vmap, gpointer data) { /* ... do something on vmap ... */ return LQR_OK; } LqrVMapList *list; list = lqr_vmap_list_start (carver); lqr_vmap_list_foreach (list, my_func, NULL); </pre></div></div><p><br class="example-break"> </p><p> In the above example, no data is actually passed on to the function. </p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p> In actual code the call to <code class="function">lqr_vmap_list_foreach</code> should be protected to test its return value, which is <code class="literal"><span class="errorcode">LQR_OK</span></code> if all <code class="function">my_func</code> calls have been successful, or it will hold the first non-successful return value from <code class="function">my_func</code>. </p></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="vmaps-objs"></a>The visibility map objects</h3></div></div></div><p> The <code class="classname">LqrVMap</code> objects contain an int buffer with the actual map data (plain array, ordered by row), plus all the information needed to be able to recover it from scratch. </p><p> The information can be extracted with these functions: </p><pre class="programlisting"> gint* <code class="function">lqr_vmap_get_data</code> (<code class="classname">LqrVMap</code>* <em class="parameter"><code>vmap</code></em>); gint <code class="function">lqr_vmap_get_width</code> (<code class="classname">LqrVMap</code>* <em class="parameter"><code>vmap</code></em>); gint <code class="function">lqr_vmap_get_height</code> (<code class="classname">LqrVMap</code>* <em class="parameter"><code>vmap</code></em>); gint <code class="function">lqr_vmap_get_orientation</code> (<code class="classname">LqrVMap</code>* <em class="parameter"><code>vmap</code></em>); gint <code class="function">lqr_vmap_get_depth</code> (<code class="classname">LqrVMap</code>* <em class="parameter"><code>vmap</code></em>); </pre><p> </p><p> The first one returns a pointer to the data buffer. </p><p> The orientation of the map is 0 if the map is to be used for horizontal rescaling, 1 otherwise. </p><p> The depth of the map is the maximum amount of rescaling possible with that map, either shrinking or enlarging. </p><p> </p><div class="example"><a name="vmap-data"></a><p class="title"><b>Example 2.9. Reading visibility maps data</b></p><div class="example-contents"><p> If we have a <code class="classname">LqrVMap</code> pointer called <em class="parameter"><code>vmap</code></em>, we could access the value at <code class="literal">(<span class="symbol">x</span>,<span class="symbol">y</span>)</code> by: </p><pre class="programlisting"> gint *buffer; gint width; gint vis; buffer = lqr_vmap_get_data (vmap); width = lqr_vmap_get_width (vmap); vis = buffer[y * width + x]; </pre><p> Uninitialised points will yield <code class="literal"><span class="symbol">vis</span> = 0</code>. For initialised points, <code class="literal"><span class="symbol">vis</span></code> will store a positive value between <code class="literal">1</code> (least visible points, the first to be carved away or to be duplicated) and <code class="literal">(<em class="parameter"><code>depth</code></em> + 1)</code> (most visible points, the last to be carved away or to be duplicated). </p><p> If the orientation is 0, the map allows resizing in the whole range form <code class="literal">(<em class="parameter"><code>width</code></em> - <em class="parameter"><code>depth</code></em>)</code> to <code class="literal">(<em class="parameter"><code>width</code></em> + <em class="parameter"><code>depth</code></em>)</code>. If the orientation is 1, the analogue formula holds with <em class="parameter"><code>height</code></em> in place of <em class="parameter"><code>width</code></em>. </p></div></div><p><br class="example-break"> </p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="import-vmap"></a>Importing a visibility map in a carver</h3></div></div></div><p> Having an <code class="classname">LqrVMap</code> object, one can load it in an <code class="classname">LqrCarver</code> simply by calling this function: </p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">LqrRetVal <b class="fsfunc">lqr_vmap_load</b>(</code></td><td>LqrCarver* <var class="pdparam">carver</var>, </td></tr><tr><td> </td><td>LqrVMap* <var class="pdparam">vmap</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><p> </p><p> The carver must not to be initialised, neither before nor after invoking this function. </p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p> This implies that the map cannot be updated, and that it will only be possible to resize the carver by an amount <em class="parameter"><code>depth</code></em> along the orientation given by <code class="function">lqr_vmap_orientation</code>. The enlargment step is also set to its maximum, 2.0. Invoking <code class="function">lqr_carver_resize</code> with an out-of-bounds argument results in a <span class="errortype">fatal</span> error (i.e. it returns <code class="literal"><span class="errorcode">LQR_ERROR</span></code>). </p></div><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p> Do not attach other carvers after you have loaded a visibility map (see also the <a class="link" href="attach-images.html" title="Attaching extra images">Attaching extra images</a> section). </p></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="save-load-vmaps"></a>Saving and loading visibility maps to/from files</h3></div></div></div><p> The library does not include methods to load/save visibility maps to/from files. However, a way to do so is shown in the demo program `<span class="application">liquidrescale</span>' in the `<code class="filename">examples</code>' directory. </p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="tuning.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="api-manual.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="attach-images.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Tuning </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Attaching extra images</td></tr></table></div></body></html>
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