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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 | <html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Overview of the library</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2"><link rel="home" href="index.html" title="The Liquid Rescale library Manual"><link rel="up" href="Introduction.html" title="Chapter 1. Introduction"><link rel="prev" href="seam-carve.html" title="Seam carving in brief"><link rel="next" href="basic.html" title="Basic methods"></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">Overview of the library</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="seam-carve.html">Prev</a> </td><th width="60%" align="center">Chapter 1. Introduction</th><td width="20%" align="right"> <a accesskey="n" href="basic.html">Next</a></td></tr></table><hr></div><div class="sect1" title="Overview of the library"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="overview"></a>Overview of the library</h2></div></div></div><p>
The Liquid Rescale library is written in C, but can be used into C++ programs without any modification. It has an
object-oriented design, so that the terminology in this manual is borrowed from C++. The central class
of the library is called <code class="classname">LqrCarver</code>. Carver objects can generate and store multi-size images, or load
them, and read them out at the desired size.
</p><p>
Internally, multi-size images are stored simply as plain images with the addition of a visibility map.
Each pixel in the image has its own visibility level. Whether to display a pixel or not simply depends
on the comparison of each pixel's visibility with a given global visibility level. In this way, images
of different sizes can be read out, simply by setting a global visibility level.
</p><p>
Therefore, once the visibility map has been computed, it allows effortless, real-time scaling. However,
visibility maps also necessarily have an orientation, either horizontal or vertical. If we want to
resize on the other direction, the visibility map has to be computed afresh, and the previous visibility
map becomes useless, because the two maps are not consistent one with the other.
</p><p>
This also implies that the resizing order affects the final result: rescaling horizontally first, then
vertically, does not yield the same result as following the reverse order. Moreover, one could choose an
intermediate way, e.g. by rescaling by one pixel in one direction, one in the other, then iterating as
needed to reach the final size.
</p><p>
The default behaviour of the library is to rescale horizontally first, then vertically, but this order
can be reversed.
</p><p>
Visibility maps can be stored in objects of type <code class="classname">LqrVMap</code>. When an <code class="classname">LqrCarver</code> object is created from
an input image, the visibility of each pixel is uninitialised. At this point, one could either import a
previously computed <code class="classname">LqrVMap</code>, or activate the <code class="classname">LqrCarver</code> so that it creates one afresh when asked to.
</p><p>
In either case, there's a single method to call, specifiying the new desired size; all the rest will
automatically be computed as necessary. By default, the visibility maps are only computed up to the
extent to which they are needed for resizing.
</p></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="seam-carve.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="Introduction.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="basic.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Seam carving in brief </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Basic methods</td></tr></table></div></body></html>
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