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<section id="io-extensions">
<h1>IO extensions<a class="headerlink" href="#io-extensions" title="Link to this heading"></a></h1>
<section id="overview">
<h2>Overview<a class="headerlink" href="#overview" title="Link to this heading"></a></h2>
<p>This extension to boost::gil provides an easy to use interface for reading and
writing various image formats. It also includes a framework for adding
new formats.</p>
<p>Please see section 3.3 for all supported image formats. A basic tutorial is
provided in section [link gil.io.tutorial Tutorial].
Also, this extension requires Boost version 1.42 and up.
Furthermore the GIL extension Toolbox is used.</p>
<p>For adding new image formats please refer to section
[link gil.io.using_io.extending_gil__io_with_new_formats Extending GIL::IO with new Formats].</p>
</section>
<section id="supported-platforms">
<h2>Supported Platforms<a class="headerlink" href="#supported-platforms" title="Link to this heading"></a></h2>
<p>All platforms supported by Boost which have a decent C++ compiler.
Depending on the image format one or more of the following image
libraries might be needed:</p>
<ul class="simple">
<li><p>libtiff</p></li>
<li><p>libjpeg</p></li>
<li><p>libpng</p></li>
<li><p>libraw</p></li>
<li><p>zlib</p></li>
</ul>
<p>The library is designed to support as many formats as required by the user.
For instance, if the user only needs bmp support none of the above mentioned
dependencies are required.</p>
<p>There are more details available in this documentation on the image format
dependencies. Please see section
[link gil.io.using_io.supported_image_formats Supported Image Formats].</p>
</section>
<section id="tutorial">
<h2>Tutorial<a class="headerlink" href="#tutorial" title="Link to this heading"></a></h2>
<p>Thanks to modern C++ programming techniques the interface for this library
is rather small and easy to use. In this tutorial I’ll give you a short
walk-around on how to use this boost::gil extension.
For more details please refer to section 3.</p>
<p>For each supported IO format a single top-level header file is provided.
For instance, include <cite>boost/gil/extension/io/tiff.hpp</cite> to be able
to read or write TIFF files.</p>
<section id="reading-an-image">
<h3>Reading An Image<a class="headerlink" href="#reading-an-image" title="Link to this heading"></a></h3>
<p>Probably the most common case to read a tiff image can be done as follows:</p>
<div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="w"> </span><span class="n">filename</span><span class="p">(</span><span class="w"> </span><span class="s">&quot;image.tif&quot;</span><span class="w"> </span><span class="p">);</span>
<span class="n">rgb8_image_t</span><span class="w"> </span><span class="n">img</span><span class="p">;</span>
<span class="n">read_image</span><span class="p">(</span><span class="w"> </span><span class="n">filename</span><span class="p">,</span><span class="w"> </span><span class="n">img</span><span class="p">,</span><span class="w"> </span><span class="n">tiff_tag</span><span class="p">()</span><span class="w"> </span><span class="p">);</span>
</pre></div>
</div>
<p>The code would be same for all other image formats. The only thing that needs
to change is the tag type ( tiff_tag ) in the read_image call.
The read_image() expects the supplied image type to be compatible with the
image stored in the file. If the user doesn’t know what format an image has she
can use read_and_convert_image().
Another important fact is that read_image() will allocate the appropriate
memory needed for the read operation. There are <code class="docutils literal notranslate"><span class="pre">read_view</span></code> or
<code class="docutils literal notranslate"><span class="pre">read_and_convert_view</span></code> counterparts, if the memory is already allocated.</p>
<p>Sometimes the user only wants to read a sub-part of an image,
then the above call would look as follows:</p>
<div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="n">read_image</span><span class="p">(</span><span class="w"> </span><span class="n">filename</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">img</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">image_read_settings</span><span class="o">&lt;</span><span class="w"> </span><span class="n">tiff_tag</span><span class="w"> </span><span class="o">&gt;</span><span class="p">(</span><span class="w"> </span><span class="n">point_t</span><span class="p">(</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">),</span><span class="w"> </span><span class="n">point_t</span><span class="p">(</span><span class="w"> </span><span class="mi">50</span><span class="p">,</span><span class="w"> </span><span class="mi">50</span><span class="w"> </span><span class="p">)</span><span class="w"> </span><span class="p">)</span>
<span class="w"> </span><span class="p">);</span>
</pre></div>
</div>
<p>The image_read_settings class will provide the user with image format
independent reading setting but can also serve as a pointer for format
dependent settings.
Please see the specific image format sections
[link gil.io.using_io.supported_image_formats Supported Image Formats]
for more details.</p>
</section>
<section id="writing-an-image">
<h3>Writing An Image<a class="headerlink" href="#writing-an-image" title="Link to this heading"></a></h3>
<p>Besides reading the information also writing is the second part of this
Boost.GIL extension. Writing is a lot simpler than reading since an existing
image view contains all the information.</p>
<p>For instance writing an image can be done as follows:</p>
<div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="w"> </span><span class="n">filename</span><span class="p">(</span><span class="w"> </span><span class="s">&quot;image.tif&quot;</span><span class="w"> </span><span class="p">);</span>
<span class="n">rgb8_image_t</span><span class="w"> </span><span class="nf">img</span><span class="p">(</span><span class="w"> </span><span class="mi">640</span><span class="p">,</span><span class="w"> </span><span class="mi">480</span><span class="w"> </span><span class="p">);</span>
<span class="c1">// write data into image</span>
<span class="n">write_view</span><span class="p">(</span><span class="w"> </span><span class="n">filename</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">view</span><span class="p">(</span><span class="w"> </span><span class="n">img</span><span class="w"> </span><span class="p">)</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">tiff_tag</span><span class="p">()</span>
<span class="w"> </span><span class="p">);</span>
</pre></div>
</div>
<p>The interface is similar to reading an image. To add image format specific
parameter the user can use <code class="docutils literal notranslate"><span class="pre">image_write_info</span></code> class.
For instance, a user can specify the JPEG quality when writing like this:</p>
<div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="w"> </span><span class="n">filename</span><span class="p">(</span><span class="w"> </span><span class="s">&quot;image.jpg&quot;</span><span class="w"> </span><span class="p">);</span>
<span class="n">rgb8_image_t</span><span class="w"> </span><span class="nf">img</span><span class="p">(</span><span class="w"> </span><span class="mi">640</span><span class="p">,</span><span class="w"> </span><span class="mi">480</span><span class="w"> </span><span class="p">);</span>
<span class="c1">// write data into image</span>
<span class="n">write_view</span><span class="p">(</span><span class="w"> </span><span class="n">filename</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">view</span><span class="p">(</span><span class="w"> </span><span class="n">img</span><span class="w"> </span><span class="p">)</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">image_write_info</span><span class="o">&lt;</span><span class="w"> </span><span class="n">jpeg_tag</span><span class="w"> </span><span class="o">&gt;</span><span class="p">(</span><span class="w"> </span><span class="mi">95</span><span class="w"> </span><span class="p">)</span>
<span class="w"> </span><span class="p">);</span>
</pre></div>
</div>
<p>The above example will write an image where the jpeg quality is
set to 95 percent.</p>
</section>
<section id="reading-and-writing-in-memory-buffers">
<h3>Reading And Writing In-Memory Buffers<a class="headerlink" href="#reading-and-writing-in-memory-buffers" title="Link to this heading"></a></h3>
<p>Reading and writing in-memory buffers are supported as well. See as follows:</p>
<div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="c1">// 1. Read an image.</span>
<span class="n">ifstream</span><span class="w"> </span><span class="n">in</span><span class="p">(</span><span class="w"> </span><span class="s">&quot;test.tif&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">ios</span><span class="o">::</span><span class="n">binary</span><span class="w"> </span><span class="p">);</span>
<span class="n">rgb8_image_t</span><span class="w"> </span><span class="n">img</span><span class="p">;</span>
<span class="n">read_image</span><span class="p">(</span><span class="w"> </span><span class="n">in</span><span class="p">,</span><span class="w"> </span><span class="n">img</span><span class="p">,</span><span class="w"> </span><span class="n">tiff_tag</span><span class="p">()</span><span class="w"> </span><span class="p">);</span>
<span class="c1">// 2. Write image to in-memory buffer.</span>
<span class="n">stringstream</span><span class="w"> </span><span class="nf">out_buffer</span><span class="p">(</span><span class="w"> </span><span class="n">ios_base</span><span class="o">::</span><span class="n">out</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">ios_base</span><span class="o">::</span><span class="n">binary</span><span class="w"> </span><span class="p">);</span>
<span class="n">rgb8_image_t</span><span class="w"> </span><span class="n">src</span><span class="p">;</span>
<span class="n">write_view</span><span class="p">(</span><span class="w"> </span><span class="n">out_buffer</span><span class="p">,</span><span class="w"> </span><span class="n">view</span><span class="p">(</span><span class="w"> </span><span class="n">src</span><span class="w"> </span><span class="p">),</span><span class="w"> </span><span class="n">tiff_tag</span><span class="p">()</span><span class="w"> </span><span class="p">);</span>
<span class="c1">// 3. Copy in-memory buffer to another.</span>
<span class="n">stringstream</span><span class="w"> </span><span class="nf">in_buffer</span><span class="p">(</span><span class="w"> </span><span class="n">ios_base</span><span class="o">::</span><span class="n">in</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">ios_base</span><span class="o">::</span><span class="n">binary</span><span class="w"> </span><span class="p">);</span>
<span class="n">in_buffer</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">out_buffer</span><span class="p">.</span><span class="n">rdbuf</span><span class="p">();</span>
<span class="c1">// 4. Read in-memory buffer to gil image</span>
<span class="n">rgb8_image_t</span><span class="w"> </span><span class="n">dst</span><span class="p">;</span>
<span class="n">read_image</span><span class="p">(</span><span class="w"> </span><span class="n">in_buffer</span><span class="p">,</span><span class="w"> </span><span class="n">dst</span><span class="p">,</span><span class="w"> </span><span class="n">tag_t</span><span class="p">()</span><span class="w"> </span><span class="p">);</span>
<span class="c1">// 5. Write out image.</span>
<span class="n">string</span><span class="w"> </span><span class="n">filename</span><span class="p">(</span><span class="w"> </span><span class="s">&quot;out.tif&quot;</span><span class="w"> </span><span class="p">);</span>
<span class="n">ofstream</span><span class="w"> </span><span class="nf">out</span><span class="p">(</span><span class="w"> </span><span class="n">filename</span><span class="p">.</span><span class="n">c_str</span><span class="p">(),</span><span class="w"> </span><span class="n">ios_base</span><span class="o">::</span><span class="n">binary</span><span class="w"> </span><span class="p">);</span>
<span class="n">write_view</span><span class="p">(</span><span class="w"> </span><span class="n">out</span><span class="p">,</span><span class="w"> </span><span class="n">view</span><span class="p">(</span><span class="w"> </span><span class="n">dst</span><span class="w"> </span><span class="p">),</span><span class="w"> </span><span class="n">tiff_tag</span><span class="p">()</span><span class="w"> </span><span class="p">);</span>
</pre></div>
</div>
<p>In case the user is using his own stream classes he has to make sure it
has the common interface read, write, seek, close, etc. interface.</p>
</section>
</section>
<section id="using-io">
<h2>Using IO<a class="headerlink" href="#using-io" title="Link to this heading"></a></h2>
<section id="general-overview">
<h3>General Overview<a class="headerlink" href="#general-overview" title="Link to this heading"></a></h3>
<p>The tutorial pointed out some use cases for reading and writing images in
various image formats. This section will provide a more thorough overview.</p>
<p>The next sections will introduce the Read and Write interface. But it might be
worth pointing out that by using some advanced metaprogramming techniques the
interface is rather small and hopefully easy to understand.</p>
<p>Besides the general interface the user also has the ability to interface
directly with the underlying image format. For that each reader or writer
provides access to the so-called backend.</p>
<p>For instance:</p>
<div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="k">typedef</span><span class="w"> </span><span class="n">bmp_tag</span><span class="w"> </span><span class="n">tag_t</span><span class="p">;</span>
<span class="k">typedef</span><span class="w"> </span><span class="n">get_reader_backend</span><span class="o">&lt;</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">string</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">tag_t</span>
<span class="w"> </span><span class="o">&gt;::</span><span class="n">type</span><span class="w"> </span><span class="n">backend_t</span><span class="p">;</span>
<span class="n">backend_t</span><span class="w"> </span><span class="n">backend</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">read_image_info</span><span class="p">(</span><span class="w"> </span><span class="n">bmp_filename</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">tag_t</span><span class="p">()</span>
<span class="w"> </span><span class="p">);</span>
<span class="n">BOOST_CHECK_EQUAL</span><span class="p">(</span><span class="w"> </span><span class="n">backend</span><span class="p">.</span><span class="n">_info</span><span class="p">.</span><span class="n">_width</span><span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="mi">127</span><span class="w"> </span><span class="p">);</span>
<span class="n">BOOST_CHECK_EQUAL</span><span class="p">(</span><span class="w"> </span><span class="n">backend</span><span class="p">.</span><span class="n">_info</span><span class="p">.</span><span class="n">_height</span><span class="p">,</span><span class="w"> </span><span class="mi">64</span><span class="w"> </span><span class="p">);</span>
</pre></div>
</div>
<p>Of course, the typedef can be removed when using c++11’s auto feature.</p>
</section>
<section id="read-interface">
<h3>Read Interface<a class="headerlink" href="#read-interface" title="Link to this heading"></a></h3>
<p>As the Tutorial demonstrated there are a few ways to read images.
Here is an enumeration of all read functions with a short description:</p>
<ul class="simple">
<li><p><code class="docutils literal notranslate"><span class="pre">read_image</span></code> - read into a gil image with no conversion.
Memory is allocated.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">read_view</span></code> - read into a gil view with no conversion.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">read_and_convert_image</span></code> - read and convert into a gil image.
Memory is allocated.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">read_and_convert_view</span></code> - read and convert into a gil view.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">read_image_info</span></code> - read the image header.</p></li>
</ul>
<p>Conversion in this context is necessary if the source (file) has an
incompatible color space with the destination (gil image type).
If that’s the case the user has to use the xxx_and_convert_xxx variants.</p>
<p>All functions take the filename or a device as the first parameter.
The filename can be anything from a C-string, <code class="docutils literal notranslate"><span class="pre">std::string</span></code>,
<code class="docutils literal notranslate"><span class="pre">std::wstring</span></code> to <code class="docutils literal notranslate"><span class="pre">std::filesystem</span></code> and <code class="docutils literal notranslate"><span class="pre">boost::filesystem</span></code> path.
The availability of the <code class="docutils literal notranslate"><span class="pre">std::filesystem</span></code> is detected automatically,
unless <code class="docutils literal notranslate"><span class="pre">BOOST_GIL_IO_USE_BOOST_FILESYSTEM</span></code> macro is defined that forces
preference of the Boost.Filesystem.
Devices could be a <code class="docutils literal notranslate"><span class="pre">FILE*</span></code>, <code class="docutils literal notranslate"><span class="pre">std::ifstream</span></code>, and <code class="docutils literal notranslate"><span class="pre">TIFF*</span></code> for TIFF images.</p>
<p>The second parameter is either an image or view type depending on the
<code class="docutils literal notranslate"><span class="pre">read_xxx</span></code> function.
The third and last parameter is either an instance of the
<code class="docutils literal notranslate"><span class="pre">image_read_settings&lt;FormatTag&gt;</span></code> or just the <code class="docutils literal notranslate"><span class="pre">FormatTag</span></code>.
The settings can be various depending on the format which is being read.
But they all share settings for reading a partial image area.
The first point describes the top left image coordinate whereas the second
are the dimensions in x and y directions.</p>
<p>Here is an example of setting up partial read:</p>
<div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="n">read_image</span><span class="p">(</span><span class="w"> </span><span class="n">filename</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">img</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">image_read_settings</span><span class="o">&lt;</span><span class="w"> </span><span class="n">tiff_tag</span><span class="w"> </span><span class="o">&gt;</span><span class="p">(</span><span class="w"> </span><span class="n">point_t</span><span class="p">(</span><span class="w"> </span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">),</span><span class="w"> </span><span class="n">point_t</span><span class="p">(</span><span class="w"> </span><span class="mi">50</span><span class="p">,</span><span class="w"> </span><span class="mi">50</span><span class="w"> </span><span class="p">)</span><span class="w"> </span><span class="p">)</span>
<span class="w"> </span><span class="p">);</span>
</pre></div>
</div>
<p>Each format supports reading just the header information,
using <code class="docutils literal notranslate"><span class="pre">read_image_info</span></code>. Please refer to the format specific sections
under 3.3. A basic example follows:</p>
<div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="n">image_read_info</span><span class="o">&lt;</span><span class="w"> </span><span class="n">tiff_t</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">info</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">read_image_info</span><span class="p">(</span><span class="w"> </span><span class="n">filename</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">tiff_t</span><span class="p">()</span>
<span class="w"> </span><span class="p">);</span>
</pre></div>
</div>
<p>GIL also comes with a dynamic image extension.
In the context of GIL.IO a user can define an <code class="docutils literal notranslate"><span class="pre">any_image</span></code> type based on
several image types. The IO extension would then pick the matching image type
to the current image file.
The following example shows this feature:</p>
<div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="n">any_image</span><span class="o">&lt;</span><span class="w"> </span><span class="n">gray8_image_t</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">gray16_image_t</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">rgb8_image_t</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">rgba8_image_t</span>
<span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">runtime_image</span><span class="p">;</span>
<span class="n">read_image</span><span class="p">(</span><span class="w"> </span><span class="n">filename</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">runtime_image</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">tiff_tag</span><span class="p">()</span>
<span class="w"> </span><span class="p">);</span>
</pre></div>
</div>
<p>During the review it became clear that there is a need to read big images
scanline by scanline. To support such use case a <code class="docutils literal notranslate"><span class="pre">scanline_reader</span></code> is
implemented for all supported image formats.
The <code class="docutils literal notranslate"><span class="pre">scanline_read_iterators</span></code> will then allow to traverse through the image.
The following code sample shows the usage:</p>
<div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="k">typedef</span><span class="w"> </span><span class="n">tiff_tag</span><span class="w"> </span><span class="n">tag_t</span><span class="p">;</span>
<span class="k">typedef</span><span class="w"> </span><span class="n">scanline_reader</span><span class="o">&lt;</span><span class="w"> </span><span class="k">typename</span><span class="w"> </span><span class="nc">get_read_device</span><span class="o">&lt;</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="kt">char</span><span class="o">*</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">tag_t</span>
<span class="w"> </span><span class="o">&gt;::</span><span class="n">type</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">tag_t</span>
<span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">reader_t</span><span class="p">;</span>
<span class="n">reader_t</span><span class="w"> </span><span class="n">reader</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">make_scanline_reader</span><span class="p">(</span><span class="w"> </span><span class="s">&quot;C:/boost/libs/gil/test/extension/io/images/tiff/test.tif&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">tag_t</span><span class="p">()</span><span class="w"> </span><span class="p">);</span>
<span class="k">typedef</span><span class="w"> </span><span class="n">rgba8_image_t</span><span class="w"> </span><span class="n">image_t</span><span class="p">;</span>
<span class="n">image_t</span><span class="w"> </span><span class="nf">dst</span><span class="p">(</span><span class="w"> </span><span class="n">reader</span><span class="p">.</span><span class="n">_info</span><span class="p">.</span><span class="n">_width</span><span class="p">,</span><span class="w"> </span><span class="n">reader</span><span class="p">.</span><span class="n">_info</span><span class="p">.</span><span class="n">_height</span><span class="w"> </span><span class="p">);</span>
<span class="n">fill_pixels</span><span class="p">(</span><span class="w"> </span><span class="n">view</span><span class="p">(</span><span class="n">dst</span><span class="p">),</span><span class="w"> </span><span class="n">image_t</span><span class="o">::</span><span class="n">value_type</span><span class="p">()</span><span class="w"> </span><span class="p">);</span>
<span class="k">typedef</span><span class="w"> </span><span class="n">reader_t</span><span class="o">::</span><span class="n">iterator_t</span><span class="w"> </span><span class="n">iterator_t</span><span class="p">;</span>
<span class="n">iterator_t</span><span class="w"> </span><span class="n">it</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">reader</span><span class="p">.</span><span class="n">begin</span><span class="p">();</span>
<span class="n">iterator_t</span><span class="w"> </span><span class="n">end</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">reader</span><span class="p">.</span><span class="n">end</span><span class="p">();</span>
<span class="k">for</span><span class="p">(</span><span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">row</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">it</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">end</span><span class="p">;</span><span class="w"> </span><span class="o">++</span><span class="n">it</span><span class="p">,</span><span class="w"> </span><span class="o">++</span><span class="n">row</span><span class="w"> </span><span class="p">)</span>
<span class="p">{</span>
<span class="w"> </span><span class="n">copy_pixels</span><span class="p">(</span><span class="w"> </span><span class="n">interleaved_view</span><span class="p">(</span><span class="w"> </span><span class="n">reader</span><span class="p">.</span><span class="n">_info</span><span class="p">.</span><span class="n">_width</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="mi">1</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="p">(</span><span class="w"> </span><span class="n">image_t</span><span class="o">::</span><span class="n">view_t</span><span class="o">::</span><span class="n">x_iterator</span><span class="w"> </span><span class="p">)</span><span class="w"> </span><span class="o">*</span><span class="n">it</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">reader</span><span class="p">.</span><span class="n">_scanline_length</span>
<span class="w"> </span><span class="p">)</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">subimage_view</span><span class="p">(</span><span class="w"> </span><span class="n">view</span><span class="p">(</span><span class="w"> </span><span class="n">dst</span><span class="w"> </span><span class="p">)</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="mi">0</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">row</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">reader</span><span class="p">.</span><span class="n">_info</span><span class="p">.</span><span class="n">_width</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="mi">1</span>
<span class="w"> </span><span class="p">)</span>
<span class="w"> </span><span class="p">);</span>
<span class="p">}</span>
</pre></div>
</div>
<p>There are many ways to traverse an image but for as of now only by
scanline is supported.</p>
</section>
<section id="write-interface">
<h3>Write Interface<a class="headerlink" href="#write-interface" title="Link to this heading"></a></h3>
<p>There is only one function for writing out images, write_view.
Similar to reading the first parameter is either a filename or a device.
The filename can be anything from a C-string, <code class="docutils literal notranslate"><span class="pre">std::string</span></code>,
<code class="docutils literal notranslate"><span class="pre">std::wstring</span></code> to <code class="docutils literal notranslate"><span class="pre">std::filesystem</span></code> and <code class="docutils literal notranslate"><span class="pre">boost::filesystem</span></code> path.
The availability of the <code class="docutils literal notranslate"><span class="pre">std::filesystem</span></code> is detected automatically,
unless <code class="docutils literal notranslate"><span class="pre">BOOST_GIL_IO_USE_BOOST_FILESYSTEM</span></code> macro is defined that forces
preference of the Boost.Filesystem.
Devices could be <code class="docutils literal notranslate"><span class="pre">FILE*</span></code>, <code class="docutils literal notranslate"><span class="pre">std::ifstream</span></code>, and <code class="docutils literal notranslate"><span class="pre">TIFF*</span></code> for TIFF images.</p>
<p>The second parameter is a view object to image being written.
The third and last parameter is either a tag or an
<code class="docutils literal notranslate"><span class="pre">image_write_info&lt;FormatTag&gt;</span></code> object containing more settings.
One example for instance is the JPEG quality.
Refer to the format specific sections under 3.3. to have a list of all
the possible settings.</p>
<p>Writing an any_image&lt;…&gt; is supported. See the following example:</p>
<div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="n">any_image</span><span class="o">&lt;</span><span class="w"> </span><span class="n">gray8_image_t</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">gray16_image_t</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">rgb8_image_t</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">rgba8_image_t</span>
<span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">runtime_image</span><span class="p">;</span>
<span class="c1">// fill any_image</span>
<span class="n">write_view</span><span class="p">(</span><span class="w"> </span><span class="n">filename</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">view</span><span class="p">(</span><span class="w"> </span><span class="n">runtime_image</span><span class="w"> </span><span class="p">)</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">tiff_tag</span><span class="p">()</span>
<span class="w"> </span><span class="p">);</span>
</pre></div>
</div>
</section>
<section id="compiler-symbols">
<h3>Compiler Symbols<a class="headerlink" href="#compiler-symbols" title="Link to this heading"></a></h3>
<p>The following table gives an overview of all supported compiler symbols
that can be set by the user:</p>
<table class="docutils align-default">
<thead>
<tr class="row-odd"><th class="head"><p>Symbol</p></th>
<th class="head"><p>Description</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p>BOOST_GIL_IO_ENABLE_GRAY_ALPHA</p></td>
<td><p>Enable the color space “gray_alpha”.</p></td>
</tr>
<tr class="row-odd"><td><p>BOOST_GIL_IO_PNG_FLOATING_POINT_SUPPORTED</p></td>
<td><p>Use libpng in floating point mode. This symbol is incompatible with BOOST_GIL_IO_PNG_FIXED_POINT_SUPPORTED.</p></td>
</tr>
<tr class="row-even"><td><p>BOOST_GIL_IO_PNG_FIXED_POINT_SUPPORTED</p></td>
<td><p>Use libpng in integer mode. This symbol is incompatible with BOOST_GIL_IO_PNG_FLOATING_POINT_SUPPORTED.</p></td>
</tr>
<tr class="row-odd"><td><p>BOOST_GIL_IO_PNG_DITHERING_SUPPORTED</p></td>
<td><p>Look up “dithering” in libpng manual for explanation.</p></td>
</tr>
<tr class="row-even"><td><p>BOOST_GIL_IO_PNG_1_4_OR_LOWER</p></td>
<td><p>Allow compiling with libpng 1.4 or lower.</p></td>
</tr>
<tr class="row-odd"><td><p>BOOST_GIL_EXTENSION_IO_JPEG_C_LIB_COMPILED_AS_CPLUSPLUS</p></td>
<td><p>libjpeg is compiled as c++ lib.</p></td>
</tr>
<tr class="row-even"><td><p>BOOST_GIL_EXTENSION_IO_PNG_C_LIB_COMPILED_AS_CPLUSPLUS</p></td>
<td><p>libpng is compiled as c++ lib.</p></td>
</tr>
<tr class="row-odd"><td><p>BOOST_GIL_EXTENSION_IO_TIFF_C_LIB_COMPILED_AS_CPLUSPLUS</p></td>
<td><p>libtiff is compiled as c++ lib.</p></td>
</tr>
<tr class="row-even"><td><p>BOOST_GIL_EXTENSION_IO_ZLIB_C_LIB_COMPILED_AS_CPLUSPLUS</p></td>
<td><p>zlib is compiled as c++ lib.</p></td>
</tr>
<tr class="row-odd"><td><p>BOOST_GIL_IO_TEST_ALLOW_READING_IMAGES</p></td>
<td><p>Allow basic test images to be read from local hard drive. The paths can be set in paths.hpp</p></td>
</tr>
<tr class="row-even"><td><p>BOOST_GIL_IO_TEST_ALLOW_WRITING_IMAGES</p></td>
<td><p>Allow images to be written to the local hard drive. The paths can be set in paths.hpp</p></td>
</tr>
<tr class="row-odd"><td><p>BOOST_GIL_IO_USE_BMP_TEST_SUITE_IMAGES</p></td>
<td><p>Run tests using the bmp test images suite. See _BMP_TEST_FILES</p></td>
</tr>
<tr class="row-even"><td><p>BOOST_GIL_IO_USE_PNG_TEST_SUITE_IMAGES</p></td>
<td><p>Run tests using the png test images suite. See _PNG_TEST_FILES</p></td>
</tr>
<tr class="row-odd"><td><p>BOOST_GIL_IO_USE_PNM_TEST_SUITE_IMAGES</p></td>
<td><p>Run tests using the pnm test images suite. Send me an email for accessing the files.</p></td>
</tr>
<tr class="row-even"><td><p>BOOST_GIL_IO_USE_TIFF_LIBTIFF_TEST_SUITE_IMAGES</p></td>
<td><p>Run tests using the targa file format test images suite. See _TIFF_LIB_TIFF_TEST_FILES</p></td>
</tr>
<tr class="row-odd"><td><p>BOOST_GIL_IO_USE_TIFF_GRAPHICSMAGICK_TEST_SUITE_IMAGES</p></td>
<td><p>Run tests using the targa file format test images suite. See _TIFF_GRAPHICSMAGICK_TEST_FILES</p></td>
</tr>
</tbody>
</table>
</section>
<section id="supported-image-formats">
<h3>Supported Image Formats<a class="headerlink" href="#supported-image-formats" title="Link to this heading"></a></h3>
<section id="bmp">
<h4>BMP<a class="headerlink" href="#bmp" title="Link to this heading"></a></h4>
<p>For a general overview of the BMP image file format go to the
following <a class="reference external" href="http://en.wikipedia.org/wiki/BMP_file_format">BMP_Wiki</a>.</p>
<p>Please note, the code has not been tested on X Windows System variations
of the BMP format which are usually referred to as XBM and XPM formats.</p>
<p>Here, only the MS Windows and OS/2 format is relevant.</p>
<p>Currently the code is able to read and write the following image types:</p>
<dl class="field-list simple">
<dt class="field-odd">Read<span class="colon">:</span></dt>
<dd class="field-odd"><p><code class="docutils literal notranslate"><span class="pre">gray1_image_t</span></code>, <code class="docutils literal notranslate"><span class="pre">gray4_image_t</span></code>, <code class="docutils literal notranslate"><span class="pre">gray8_image_t</span></code>, <code class="docutils literal notranslate"><span class="pre">rgb8_image_t</span></code> and <code class="docutils literal notranslate"><span class="pre">rgba8_image_t</span></code></p>
</dd>
<dt class="field-even">Write<span class="colon">:</span></dt>
<dd class="field-even"><p><code class="docutils literal notranslate"><span class="pre">rgb8_image_t</span></code> and <code class="docutils literal notranslate"><span class="pre">rgba8_image_t</span></code></p>
</dd>
</dl>
<p>The lack of having an indexed image type in gil restricts the current
interface to only write out non-indexed images.
This is subject to change soon.</p>
</section>
<section id="jpeg">
<h4>JPEG<a class="headerlink" href="#jpeg" title="Link to this heading"></a></h4>
<p>For a general overview of the JPEG image file format go to the
following <a class="reference external" href="http://en.wikipedia.org/wiki/JPEG">JPEG_Wiki</a>.</p>
<p>This jpeg extension is based on the libjpeg library which can be
found here, <a class="reference external" href="http://www.ijg.org/">JPEG_Lib</a>.</p>
<p>All versions starting from 8x are supported.</p>
<p>The user has to make sure this library is properly installed.
I strongly recommend the user to build the library yourself.
It could potentially save you a lot of trouble.</p>
<p>Currently the code is able to read and write the following image types:</p>
<dl class="field-list simple">
<dt class="field-odd">Read<span class="colon">:</span></dt>
<dd class="field-odd"><p><code class="docutils literal notranslate"><span class="pre">gray8_image_t</span></code>, <code class="docutils literal notranslate"><span class="pre">rgb8_image_t</span></code>, <code class="docutils literal notranslate"><span class="pre">cmyk8_image_t</span></code></p>
</dd>
<dt class="field-even">Write<span class="colon">:</span></dt>
<dd class="field-even"><p><code class="docutils literal notranslate"><span class="pre">gray8_image_t</span></code>, <code class="docutils literal notranslate"><span class="pre">rgb8_image_t</span></code>, <code class="docutils literal notranslate"><span class="pre">cmyk8_image_t</span></code></p>
</dd>
</dl>
<p>Reading YCbCr or YCCK images is possible but might result in inaccuracies since
both color spaces aren’t available yet for gil.
For now these color spaces are read as rgb images.
This is subject to change soon.</p>
</section>
<section id="png">
<h4>PNG<a class="headerlink" href="#png" title="Link to this heading"></a></h4>
<p>For a general overview of the PNG image file format go to the
following <a class="reference external" href="http://en.wikipedia.org/wiki/Portable_Network_Graphics">PNG_Wiki</a>.</p>
<p>This png extension is based on the libpng, which can be found
here, <a class="reference external" href="http://libpng.org/pub/png/libpng.html">PNG_Lib</a>.</p>
<p>All versions starting from 1.5.x are supported.</p>
<p>The user has to make sure this library is properly installed.
I strongly recommend the user to build the library yourself.
It could potentially save you a lot of trouble.</p>
<p>Currently the code is able to read and write the following image types:</p>
<dl class="field-list simple">
<dt class="field-odd">Read<span class="colon">:</span></dt>
<dd class="field-odd"><p>gray1, gray2, gray4, gray8, gray16, gray_alpha_8, gray_alpha_16, rgb8, rgb16, rgba8, rgba16</p>
</dd>
<dt class="field-even">Write<span class="colon">:</span></dt>
<dd class="field-even"><p>gray1, gray2, gray4, gray8, gray16, gray_alpha_8, gray_alpha_16, rgb8, rgb16, rgba8, rgba16</p>
</dd>
</dl>
<p>For reading gray_alpha images the user has to compile application with <code class="docutils literal notranslate"><span class="pre">BOOST_GIL_IO_ENABLE_GRAY_ALPHA</span></code>
macro defined. This color space is defined in the toolbox by using <code class="docutils literal notranslate"><span class="pre">gray_alpha.hpp</span></code>.</p>
</section>
<section id="pnm">
<h4>PNM<a class="headerlink" href="#pnm" title="Link to this heading"></a></h4>
<p>For a general overview of the PNM image file format go to the
following <a class="reference external" href="http://en.wikipedia.org/wiki/Portable_anymap">PNM_Wiki</a>. No external library is needed for the pnm format.</p>
<p>The extension can read images in both flavours of the formats, ASCII and binary,
that is types from P1 through P6; can write only binary formats.</p>
<p>Currently the code is able to read and write the following image types:</p>
<dl class="field-list simple">
<dt class="field-odd">Read<span class="colon">:</span></dt>
<dd class="field-odd"><p>gray1, gray8, rgb8</p>
</dd>
<dt class="field-even">Write<span class="colon">:</span></dt>
<dd class="field-even"><p>gray1, gray8, rgb8</p>
</dd>
</dl>
<p>When reading a mono text image the data is read as a gray8 image.</p>
</section>
<section id="raw">
<h4>RAW<a class="headerlink" href="#raw" title="Link to this heading"></a></h4>
<p>For a general overview see <a class="reference external" href="http://en.wikipedia.org/wiki/Raw_image_format">RAW_Wiki</a>.</p>
<p>Currently the extension is only able to read rgb8 images.</p>
</section>
<section id="targa">
<h4>TARGA<a class="headerlink" href="#targa" title="Link to this heading"></a></h4>
<p>For a general overview of the BMP image file format go to the
following <a class="reference external" href="http://en.wikipedia.org/wiki/Truevision_TGA">TARGA_Wiki</a>.</p>
<p>Currently the code is able to read and write the following image types:</p>
<dl class="field-list simple">
<dt class="field-odd">Read<span class="colon">:</span></dt>
<dd class="field-odd"><p>rgb8_image_t and rgba8_image_t</p>
</dd>
<dt class="field-even">Write<span class="colon">:</span></dt>
<dd class="field-even"><p>rgb8_image_t and rgba8_image_t</p>
</dd>
</dl>
<p>The lack of having an indexed image type in gil restricts the current
interface to only write out non-indexed images.
This is subject to change soon.</p>
</section>
<section id="tiff">
<h4>TIFF<a class="headerlink" href="#tiff" title="Link to this heading"></a></h4>
<p>For a general overview of the TIFF image file format go to the
following <a class="reference external" href="http://en.wikipedia.org/wiki/Tagged_Image_File_Format">TIFF_Wiki</a>.</p>
<p>This tiff extension is based on the libtiff, which can be found, <a class="reference external" href="http://www.remotesensing.org/libtiff/">TIFF_Lib</a>.</p>
<p>All versions starting from 3.9.x are supported.</p>
<p>The user has to make sure this library is properly installed. I strongly
recommend the user to build the library yourself. It could potentially
save you a lot of trouble.</p>
<p>TIFF images can virtually encode all kinds of channel sizes representing
various color spaces. Even planar images are possible.
For instance, <code class="docutils literal notranslate"><span class="pre">rbg323</span></code> or <code class="docutils literal notranslate"><span class="pre">gray7</span></code>. The channels also can have specific
formats, like integer values or floating point values.</p>
<p>For a complete set of options please consult the following websites:</p>
<ul class="simple">
<li><p><a class="reference external" href="http://www.awaresystems.be/imaging/tiff/tifftags/baseline.html">TIFF_Base_Tags</a></p></li>
<li><p><a class="reference external" href="http://www.awaresystems.be/imaging/tiff/tifftags/extension.html">TIFF_Extension_Tags</a></p></li>
</ul>
<p>The author of this extension is not claiming all tiff formats are supported.
This extension is likely to be a moving target adding new features with each
new milestone. Here is an incomplete list:</p>
<ul class="simple">
<li><p>Multi-page TIFF - read only</p></li>
<li><p>Strip TIFF - read and write support</p></li>
<li><p>Tiled TIFF - read and write support with user defined tiled sizes</p></li>
<li><p>Bit images TIFF - fully supported, like <code class="docutils literal notranslate"><span class="pre">gray1_image_t</span></code> (minisblack)</p></li>
<li><p>Planar TIFF - fully supported</p></li>
<li><p>Floating-point TIFF - fully supported</p></li>
<li><p>Palette TIFF - supported but no indexed image type is available as of now</p></li>
</ul>
<p>This gil extension uses two different test image suites to test read and
write capabilities. See <code class="docutils literal notranslate"><span class="pre">test_image</span></code> folder.
It’s advisable to use ImageMagick test viewer to display images.</p>
</section>
</section>
<section id="extending-gil-io-with-new-formats">
<h3>Extending GIL::IO with new Formats<a class="headerlink" href="#extending-gil-io-with-new-formats" title="Link to this heading"></a></h3>
<p>Extending the gil::io with new formats is meant to be simple and
straightforward. Before adding I would recommend to have a look at existing
implementations and then trying to follow a couple of guidelines:</p>
<ul>
<li><dl class="simple">
<dt>Create the following files for your new xxx format</dt><dd><ul class="simple">
<li><p><code class="docutils literal notranslate"><span class="pre">xxx_read.hpp</span></code> - only includes read code</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">xxx_write.hpp</span></code> - only includes write code</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">xxx_all.hpp</span></code> - includes xxx_read.hpp and xxx_write.hpp</p></li>
</ul>
</dd>
</dl>
</li>
<li><p>Add the code to the <code class="docutils literal notranslate"><span class="pre">boost::gil::detail</span></code> namespace</p></li>
<li><p>Create a tag type for the new format. Like this:</p>
<div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="k">struct</span><span class="w"> </span><span class="nc">xxx_tag</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">format_tag</span><span class="w"> </span><span class="p">{};</span>
</pre></div>
</div>
</li>
<li><p>Create the image_read_info for the new format. It contains all the
information that is necessary to read an image. It should be filled
and returned by the <code class="docutils literal notranslate"><span class="pre">get_info</span></code> member of the reader class. See below:</p>
<div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="k">template</span><span class="o">&lt;&gt;</span><span class="w"> </span><span class="k">struct</span><span class="w"> </span><span class="nc">image_read_info</span><span class="o">&lt;</span><span class="w"> </span><span class="n">xxx_tag</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="p">{};</span>
</pre></div>
</div>
</li>
<li><p>Create the image_write_info for the new format. It contains all the
information that is necessary to write an image:</p>
<div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="k">template</span><span class="o">&lt;&gt;</span><span class="w"> </span><span class="k">struct</span><span class="w"> </span><span class="nc">image_write_info</span><span class="o">&lt;</span><span class="w"> </span><span class="n">xxx_tag</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="p">{};</span>
</pre></div>
</div>
</li>
<li><p>Use the following reader skeleton as a start:</p>
<div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="k">template</span><span class="o">&lt;</span><span class="w"> </span><span class="k">typename</span><span class="w"> </span><span class="nc">Device</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="k">typename</span><span class="w"> </span><span class="nc">ConversionPolicy</span>
<span class="w"> </span><span class="o">&gt;</span>
<span class="k">class</span><span class="w"> </span><span class="nc">reader</span><span class="o">&lt;</span><span class="w"> </span><span class="n">Device</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">xxx_tag</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">ConversionPolicy</span>
<span class="w"> </span><span class="o">&gt;</span>
<span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="k">public</span><span class="w"> </span><span class="n">reader_base</span><span class="o">&lt;</span><span class="w"> </span><span class="n">xxx_tag</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">ConversionPolicy</span>
<span class="w"> </span><span class="o">&gt;</span>
<span class="p">{</span>
<span class="k">private</span><span class="o">:</span>
<span class="w"> </span><span class="k">typedef</span><span class="w"> </span><span class="k">typename</span><span class="w"> </span><span class="nc">ConversionPolicy</span><span class="o">::</span><span class="n">color_converter_type</span><span class="w"> </span><span class="n">cc_t</span><span class="p">;</span>
<span class="k">public</span><span class="o">:</span>
<span class="w"> </span><span class="n">reader</span><span class="p">(</span><span class="w"> </span><span class="n">Device</span><span class="o">&amp;</span><span class="w"> </span><span class="n">device</span><span class="w"> </span><span class="p">)</span>
<span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">_io_dev</span><span class="p">(</span><span class="w"> </span><span class="n">device</span><span class="w"> </span><span class="p">)</span>
<span class="w"> </span><span class="p">{}</span>
<span class="w"> </span><span class="n">reader</span><span class="p">(</span><span class="w"> </span><span class="n">Device</span><span class="o">&amp;</span><span class="w"> </span><span class="n">device</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">cc_t</span><span class="o">&amp;</span><span class="w"> </span><span class="n">cc</span>
<span class="w"> </span><span class="p">)</span>
<span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">_io_dev</span><span class="p">(</span><span class="w"> </span><span class="n">device</span><span class="w"> </span><span class="p">)</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">reader_base</span><span class="o">&lt;</span><span class="w"> </span><span class="n">xxx_tag</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">ConversionPolicy</span>
<span class="w"> </span><span class="o">&gt;</span><span class="p">(</span><span class="w"> </span><span class="n">cc</span><span class="w"> </span><span class="p">)</span>
<span class="w"> </span><span class="p">{}</span>
<span class="w"> </span><span class="n">image_read_info</span><span class="o">&lt;</span><span class="w"> </span><span class="n">xxx_tag</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">get_info</span><span class="p">()</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">// your implementation here</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="k">template</span><span class="o">&lt;</span><span class="w"> </span><span class="k">typename</span><span class="w"> </span><span class="nc">View</span><span class="w"> </span><span class="o">&gt;</span>
<span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="n">apply</span><span class="p">(</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">View</span><span class="o">&amp;</span><span class="w"> </span><span class="n">dst_view</span><span class="w"> </span><span class="p">)</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">// your implementation here</span>
<span class="w"> </span><span class="p">}</span>
<span class="p">};</span>
</pre></div>
</div>
</li>
<li><p>The writer skeleton:</p>
<div class="highlight-c++ notranslate"><div class="highlight"><pre><span></span><span class="k">template</span><span class="o">&lt;</span><span class="w"> </span><span class="k">typename</span><span class="w"> </span><span class="nc">Device</span><span class="w"> </span><span class="o">&gt;</span>
<span class="k">class</span><span class="w"> </span><span class="nc">writer</span><span class="o">&lt;</span><span class="w"> </span><span class="n">Device</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="n">xxx_tag</span>
<span class="w"> </span><span class="o">&gt;</span>
<span class="p">{</span>
<span class="k">public</span><span class="o">:</span>
<span class="w"> </span><span class="n">writer</span><span class="p">(</span><span class="w"> </span><span class="n">Device</span><span class="w"> </span><span class="o">&amp;</span><span class="w"> </span><span class="n">file</span><span class="w"> </span><span class="p">)</span>
<span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">out</span><span class="p">(</span><span class="n">file</span><span class="p">)</span>
<span class="w"> </span><span class="p">{}</span>
<span class="w"> </span><span class="k">template</span><span class="o">&lt;</span><span class="k">typename</span><span class="w"> </span><span class="nc">View</span><span class="o">&gt;</span>
<span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="n">apply</span><span class="p">(</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">View</span><span class="o">&amp;</span><span class="w"> </span><span class="n">view</span><span class="w"> </span><span class="p">)</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">// your implementation here</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="k">template</span><span class="o">&lt;</span><span class="k">typename</span><span class="w"> </span><span class="nc">View</span><span class="o">&gt;</span>
<span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="n">apply</span><span class="p">(</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">View</span><span class="o">&amp;</span><span class="w"> </span><span class="n">view</span>
<span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">image_write_info</span><span class="o">&lt;</span><span class="w"> </span><span class="n">xxx_tag</span><span class="w"> </span><span class="o">&gt;&amp;</span><span class="w"> </span><span class="n">info</span><span class="w"> </span><span class="p">)</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">// your implementation here</span>
<span class="w"> </span><span class="p">}</span>
<span class="p">};</span>
</pre></div>
</div>
</li>
</ul>
</section>
</section>
<section id="running-gil-io-tests">
<h2>Running gil::io tests<a class="headerlink" href="#running-gil-io-tests" title="Link to this heading"></a></h2>
<p>gil::io comes with a large suite of test cases which reads and writes various
file formats. It uses some test image suites which can be found online or
which can be demanded from me by sending me an email.</p>
<p>There are some test images created by me in the test folder.
To enable unit tests which make use of them set the following compiler options
<code class="docutils literal notranslate"><span class="pre">BOOST_GIL_IO_TEST_ALLOW_READING_IMAGES</span></code> and
<code class="docutils literal notranslate"><span class="pre">BOOST_GIL_IO_TEST_ALLOW_WRITING_IMAGES</span></code>.</p>
<p>The following list provides all links to the image suites the compiler symbol
to enable the tests:</p>
<dl class="field-list simple">
<dt class="field-odd">BMP<span class="colon">:</span></dt>
<dd class="field-odd"><p><a class="reference external" href="http://entropymine.com/jason/bmpsuite/">BMP_TEST_FILES</a> – BOOST_GIL_IO_USE_BMP_TEST_SUITE_IMAGES</p>
</dd>
<dt class="field-even">PNG<span class="colon">:</span></dt>
<dd class="field-even"><p><a class="reference external" href="http://www.schaik.com/pngsuite/pngsuite.html">PNG_TEST_FILES</a> – BOOST_GIL_IO_USE_PNG_TEST_SUITE_IMAGES</p>
</dd>
<dt class="field-odd">PNM<span class="colon">:</span></dt>
<dd class="field-odd"><p>request files from me – BOOST_GIL_IO_USE_PNM_TEST_SUITE_IMAGES</p>
</dd>
<dt class="field-even">TIFF<span class="colon">:</span></dt>
<dd class="field-even"><p><a class="reference external" href="http://www.remotesensing.org/libtiff/images.html">TIFF_LIB_TIFF_TEST_FILES</a> – BOOST_GIL_IO_USE_TIFF_LIBTIFF_TEST_SUITE_IMAGES</p>
</dd>
<dt class="field-odd">TIFF<span class="colon">:</span></dt>
<dd class="field-odd"><p><a class="reference external" href="ftp://ftp.graphicsmagick.org/pub/tiff-samples/tiff-sample-images-be.tar.gz">TIFF_GRAPHICSMAGICK_TEST_FILES</a> – BOOST_GIL_IO_USE_TIFF_GRAPHICSMAGICK_TEST_SUITE_IMAGES</p>
</dd>
</dl>
</section>
</section>
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