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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 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 | <html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Reading the multi-size image</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><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="lqr.html" title="Liquid rescaling"><link rel="next" href="energy.html" title="Automatic feature detection"></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">Reading the multi-size image</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="lqr.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="energy.html">Next</a></td></tr></table><hr></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="read-out"></a>Reading the multi-size image</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="read-out.html#px-by-px">Pixel by pixel</a></span></dt><dt><span class="sect2"><a href="read-out.html#line-by-line">One line at a time</a></span></dt><dt><span class="sect2"><a href="read-out.html#reset">Resetting</a></span></dt></dl></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="px-by-px"></a>Pixel by pixel</h3></div></div></div><p>
Once you have rescaled the image, you can read out the result through the functions:
</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">gboolean <b class="fsfunc">lqr_carver_scan</b>(</code></td><td> LqrCarver * <var class="pdparam">carver</var>, </td></tr><tr><td> </td><td> gint* <var class="pdparam">x</var>, </td></tr><tr><td> </td><td> gint* <var class="pdparam">y</var>, </td></tr><tr><td> </td><td> guchar** <var class="pdparam">rgb</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><p>
or
</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">gboolean <b class="fsfunc">lqr_carver_scan_ext</b>(</code></td><td> LqrCarver * <var class="pdparam">carver</var>, </td></tr><tr><td> </td><td> gint* <var class="pdparam">x</var>, </td></tr><tr><td> </td><td> gint* <var class="pdparam">y</var>, </td></tr><tr><td> </td><td> void** <var class="pdparam">rgb</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><p>
</p><p>
Here, <em class="parameter"><code>x</code></em> and <em class="parameter"><code>y</code></em> are pointers to the varaibles which will
hold the pixel coordinate, while <em class="parameter"><code>rgb</code></em> is a pointer to an array which will
contain the pixel colour information. If the carver was created using the standard 8-bit constructor
<code class="function">lqr_carver_new</code>, the first form can be used, otherwise you must use the extended
form <code class="function">lqr_carver_scan_ext</code>. In this last case, the output pointer
<em class="parameter"><code>rgb</code></em> must be passed as a pointer to <span class="type">void*</span>, but the outcome should
actually be cast to a pointer to an array of the appropriate type, depending on the <code class="classname">LqrCarver</code>
colour depth.
</p><p>
The return value is <code class="literal"><span class="returnvalue">FALSE</span></code> when the end of the image is reached, or the buffer has the wrong
number of bits, <code class="literal"><span class="returnvalue">TRUE</span></code> otherwise.
</p><p>
Each time these functions are invoked, they will store the coordinates and rgb information in the
output pointers and move to the next pixel. If they reach the end, they reset the reader and return
<code class="literal"><span class="returnvalue">FALSE</span></code>.
</p><p>
Here is a sample code usage:
</p><div class="example"><a name="ex-read-out"></a><p class="title"><b>Example 2.1. A simple readout example</b></p><div class="example-contents"><pre class="programlisting">
gint x, y;
guchar *rgb;
while (lqr_carver_scan (carver, &x, &y, &rgb) {
my_plot (x, y, rgb[0], rgb[1], rgb[2]);
}
</pre></div></div><p><br class="example-break">
In this example, it is assumed that the image has three 8-bit colour channels, and that there exist
some function <code class="function">my_plot</code> which writes out the pixels somewhere.
</p><p>
The same readout example with different colour depth would read like this:
</p><div class="example"><a name="ex-read-out-ext"></a><p class="title"><b>Example 2.2. A simple readout example - extended version</b></p><div class="example-contents"><pre class="programlisting">
gint x, y;
void *rgb;
gdouble *rgb_out;
while (lqr_carver_scan (carver, &x, &y, &rgb) {
rgb_out = (gdouble*) rgb;
my_plot (x, y, rgb_out[0], rgb_out[1], rgb_out[2]);
}
</pre></div></div><p><br class="example-break">
In this example it is assumed that the carver was loaded with the <code class="literal">LQR_COLDEPTH_64F</code> as the
<em class="parameter"><code>colour_depth</code></em> argument in the constructor
<code class="function">lqr_carver_new_ext</code>, and that it has <code class="literal">3</code> colour channels (see
the <a class="link" href="generate-multi-size.html#carver-new" title="Carver object creation">constructor section</a> for details); therefore, the output is
cast to type <span class="type">gdouble</span> before using it.
</p><div class="important" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Important</h3><p>
The <em class="parameter"><code>rgb</code></em> array is owned by to the carver object, so it doesn't need
initialization, as in the example. Indeed, it must be used for read-only purposes, and the
content should always be copyed after each call to a scan function.
</p></div></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="line-by-line"></a>One line at a time</h3></div></div></div><p>
The image can also be read one line at a time, but it is not possible to freely decide if it is to
be read by row or by column. Instead, this has to be queried 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">gboolean <b class="fsfunc">lqr_carver_scan_by_row</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 function returns <code class="literal"><span class="returnvalue">TRUE</span></code> if the image is read by row, and <code class="literal"><span class="returnvalue">FALSE</span></code> if it is read by
column.
</p><p>
Then, the image can be read through these functions:
</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">gboolean <b class="fsfunc">lqr_carver_scan_line</b>(</code></td><td>LqrCarver* <var class="pdparam">carver</var>, </td></tr><tr><td> </td><td>gint* <var class="pdparam">n</var>, </td></tr><tr><td> </td><td>guchar** <var class="pdparam">rgb</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><p>
or
</p><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">gboolean <b class="fsfunc">lqr_carver_scan_line_ext</b>(</code></td><td>LqrCarver* <var class="pdparam">carver</var>, </td></tr><tr><td> </td><td>gint* <var class="pdparam">n</var>, </td></tr><tr><td> </td><td>void** <var class="pdparam">rgb</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><p>
</p><p>
These functions work exactly the same way as <code class="function">lqr_carver_scan</code> and
<code class="function">lqr_carver_scan_ext</code>, but only one coordinate is stored (either the row or the
column number), and the <em class="parameter"><code>rgb</code></em> array will contain a whole line.
</p><p>
Here is a sample code usage for the standard 8-bit case:
</p><div class="example"><a name="ex-scan-line"></a><p class="title"><b>Example 2.3. Line-by-line readout example</b></p><div class="example-contents"><pre class="programlisting">
gint n;
guchar *rgb;
gboolean by_row;
by_row = lqr_carver_scan_by_row (carver);
while (lqr_carver_scan_line (carver, &n, &rgb) {
by_row ? my_plot_row (n, rgb) : my_plot_col (n, rgb);
}
</pre></div></div><p><br class="example-break">
where, as before, it is assumed that the <code class="function">my_plot_row</code> and
<code class="function">my_plot_col</code> functions have been previously defined and "know what to do".
</p><p>
The extended version for images with more colour depth is very similar, it only requires an
additional cast:
</p><div class="example"><a name="ex-scan-line-ext"></a><p class="title"><b>Example 2.4. Line-by-line readout example - extended version</b></p><div class="example-contents"><pre class="programlisting">
gint n;
void *rgb;
guchar *rgb_out;
gboolean by_row;
by_row = lqr_carver_scan_by_row (carver);
while (lqr_carver_scan_line_ext (carver, &n, &rgb) {
rgb_out = (gboolean*) rgb;
by_row ? my_plot_row (n, rgb_out) : my_plot_col (n, rgb_out);
}
</pre></div></div><p><br class="example-break">
</p></div><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a name="reset"></a>Resetting</h3></div></div></div><p>
Normally, it is not needed to reset the image scan. However, if the scan has been stopped at same
intermediate step for some reason, the following function can be used to restart from the beginning:
</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_scan_reset</b>(</code></td><td>LqrCarver* <var class="pdparam">carver</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div><p>
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