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| <a href="#libvips-callback.synopsis" class="shortcut">Top</a> |
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| <a href="#libvips-callback.description" class="shortcut">Description</a> |
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| <div class="refentry" title="callback"> |
| <a name="libvips-callback"></a><div class="titlepage"></div> |
| <div class="refnamediv"><table width="100%"><tr> |
| <td valign="top"> |
| <h2><span class="refentrytitle"><a name="libvips-callback.top_of_page"></a>callback</span></h2> |
| <p>callback — image callbacks</p> |
| </td> |
| <td valign="top" align="right"></td> |
| </tr></table></div> |
| <div class="refsect1" title="Stability Level"> |
| <a name="libvips-callback.stability-level"></a><h2>Stability Level</h2> |
| Stable, unless otherwise indicated |
| </div> |
| <div class="refsynopsisdiv" title="Synopsis"> |
| <a name="libvips-callback.synopsis"></a><h2>Synopsis</h2> |
| <pre class="synopsis"> |
| #include <vips/vips.h> |
| |
| <span class="returnvalue">int</span> (<a class="link" href="libvips-callback.html#im-callback-fn" title="im_callback_fn ()">*im_callback_fn</a>) (<em class="parameter"><code><span class="type">void</span> *a</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *b</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-callback.html#im-add-close-callback" title="im_add_close_callback ()">im_add_close_callback</a> (<em class="parameter"><code><span class="type">IMAGE</span> *im</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-callback.html#im-callback-fn" title="im_callback_fn ()"><span class="type">im_callback_fn</span></a> fn</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *a</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *b</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-callback.html#im-add-preclose-callback" title="im_add_preclose_callback ()">im_add_preclose_callback</a> (<em class="parameter"><code><span class="type">IMAGE</span> *im</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-callback.html#im-callback-fn" title="im_callback_fn ()"><span class="type">im_callback_fn</span></a> fn</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *a</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *b</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-callback.html#im-add-postclose-callback" title="im_add_postclose_callback ()">im_add_postclose_callback</a> (<em class="parameter"><code><span class="type">IMAGE</span> *im</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-callback.html#im-callback-fn" title="im_callback_fn ()"><span class="type">im_callback_fn</span></a> fn</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *a</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *b</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-callback.html#im-add-written-callback" title="im_add_written_callback ()">im_add_written_callback</a> (<em class="parameter"><code><span class="type">IMAGE</span> *im</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-callback.html#im-callback-fn" title="im_callback_fn ()"><span class="type">im_callback_fn</span></a> fn</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *a</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *b</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-callback.html#im-add-evalstart-callback" title="im_add_evalstart_callback ()">im_add_evalstart_callback</a> (<em class="parameter"><code><span class="type">IMAGE</span> *im</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-callback.html#im-callback-fn" title="im_callback_fn ()"><span class="type">im_callback_fn</span></a> fn</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *a</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *b</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-callback.html#im-add-eval-callback" title="im_add_eval_callback ()">im_add_eval_callback</a> (<em class="parameter"><code><span class="type">IMAGE</span> *im</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-callback.html#im-callback-fn" title="im_callback_fn ()"><span class="type">im_callback_fn</span></a> fn</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *a</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *b</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-callback.html#im-add-evalend-callback" title="im_add_evalend_callback ()">im_add_evalend_callback</a> (<em class="parameter"><code><span class="type">IMAGE</span> *im</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-callback.html#im-callback-fn" title="im_callback_fn ()"><span class="type">im_callback_fn</span></a> fn</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *a</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *b</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-callback.html#im-add-invalidate-callback" title="im_add_invalidate_callback ()">im_add_invalidate_callback</a> (<em class="parameter"><code><span class="type">IMAGE</span> *im</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-callback.html#im-callback-fn" title="im_callback_fn ()"><span class="type">im_callback_fn</span></a> fn</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *a</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *b</code></em>); |
| </pre> |
| </div> |
| <div class="refsect1" title="Description"> |
| <a name="libvips-callback.description"></a><h2>Description</h2> |
| <p> |
| Images trigger various callbacks at various points in their lifetime. You |
| can register callbacks and be notified of various events, such as |
| evaluation progress or close. |
| </p> |
| <p> |
| Callbacks should return 0 for success, or -1 on error, setting an error |
| message with <a class="link" href="libvips-error.html#im-error" title="im_error ()"><code class="function">im_error()</code></a>. |
| </p> |
| </div> |
| <div class="refsect1" title="Details"> |
| <a name="libvips-callback.details"></a><h2>Details</h2> |
| <div class="refsect2" title="im_callback_fn ()"> |
| <a name="im-callback-fn"></a><h3>im_callback_fn ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> (*im_callback_fn) (<em class="parameter"><code><span class="type">void</span> *a</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *b</code></em>);</pre> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_add_close_callback ()"> |
| <a name="im-add-close-callback"></a><h3>im_add_close_callback ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_add_close_callback (<em class="parameter"><code><span class="type">IMAGE</span> *im</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-callback.html#im-callback-fn" title="im_callback_fn ()"><span class="type">im_callback_fn</span></a> fn</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *a</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *b</code></em>);</pre> |
| <p> |
| Attaches a close callback <em class="parameter"><code>fn</code></em> to <em class="parameter"><code>im</code></em>. |
| </p> |
| <p> |
| Close callbacks are triggered exactly once, when the image has been closed |
| and most resources freed, but just before the memory for <em class="parameter"><code>im</code></em> is released. |
| </p> |
| <p> |
| Close callbacks are a good place to free memory that was need to generate |
| <em class="parameter"><code>im</code></em>. You can close other images and there |
| may even be circularity in your close lists. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-memory.html#im-malloc" title="im_malloc ()"><code class="function">im_malloc()</code></a> (implemented with <a class="link" href="libvips-callback.html#im-add-close-callback" title="im_add_close_callback ()"><code class="function">im_add_close_callback()</code></a>), |
| <a class="link" href="libvips-callback.html#im-add-preclose-callback" title="im_add_preclose_callback ()"><code class="function">im_add_preclose_callback()</code></a> (called earlier in the image close process), |
| <a class="link" href="libvips-memory.html#im-free" title="im_free ()"><code class="function">im_free()</code></a>. |
| </p> |
| <div class="variablelist"><table border="0"> |
| <col align="left" valign="top"> |
| <tbody> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>im</code></em> :</span></p></td> |
| <td>image to attach callback to |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>fn</code></em> :</span></p></td> |
| <td>callback function |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>a</code></em> :</span></p></td> |
| <td>user data 1 |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>b</code></em> :</span></p></td> |
| <td>user data 2 |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, or -1 on error. |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_add_preclose_callback ()"> |
| <a name="im-add-preclose-callback"></a><h3>im_add_preclose_callback ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_add_preclose_callback (<em class="parameter"><code><span class="type">IMAGE</span> *im</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-callback.html#im-callback-fn" title="im_callback_fn ()"><span class="type">im_callback_fn</span></a> fn</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *a</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *b</code></em>);</pre> |
| <p> |
| Attaches a pre-close callback <em class="parameter"><code>fn</code></em> to <em class="parameter"><code>im</code></em>. |
| </p> |
| <p> |
| Pre-close callbacks are triggered exactly once just before an image is |
| closed. The image is still valid and you can do anything with it, except |
| stop close from happening. |
| </p> |
| <p> |
| Pre-close callbacks are a good place for languae bindings to break as |
| association between the language object and the VIPS image. |
| </p> |
| <div class="variablelist"><table border="0"> |
| <col align="left" valign="top"> |
| <tbody> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>im</code></em> :</span></p></td> |
| <td>image to attach callback to |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>fn</code></em> :</span></p></td> |
| <td>callback function |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>a</code></em> :</span></p></td> |
| <td>user data 1 |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>b</code></em> :</span></p></td> |
| <td>user data 2 |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, or -1 on error. |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_add_postclose_callback ()"> |
| <a name="im-add-postclose-callback"></a><h3>im_add_postclose_callback ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_add_postclose_callback (<em class="parameter"><code><span class="type">IMAGE</span> *im</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-callback.html#im-callback-fn" title="im_callback_fn ()"><span class="type">im_callback_fn</span></a> fn</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *a</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *b</code></em>);</pre> |
| <p> |
| Attaches a close callback <em class="parameter"><code>fn</code></em> to <em class="parameter"><code>im</code></em>. |
| </p> |
| <p> |
| Post-close callbacks are triggered exactly once, just before the memory |
| associated with <em class="parameter"><code>im</code></em> is released. |
| </p> |
| <p> |
| Close callbacks are a good place to delete temporary files. You can close |
| other images and there may even be circularity in your close lists. |
| </p> |
| <div class="variablelist"><table border="0"> |
| <col align="left" valign="top"> |
| <tbody> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>im</code></em> :</span></p></td> |
| <td>image to attach callback to |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>fn</code></em> :</span></p></td> |
| <td>callback function |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>a</code></em> :</span></p></td> |
| <td>user data 1 |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>b</code></em> :</span></p></td> |
| <td>user data 2 |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, or -1 on error. |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_add_written_callback ()"> |
| <a name="im-add-written-callback"></a><h3>im_add_written_callback ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_add_written_callback (<em class="parameter"><code><span class="type">IMAGE</span> *im</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-callback.html#im-callback-fn" title="im_callback_fn ()"><span class="type">im_callback_fn</span></a> fn</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *a</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *b</code></em>);</pre> |
| <p> |
| Attaches a written callback <em class="parameter"><code>fn</code></em> to <em class="parameter"><code>im</code></em>. |
| </p> |
| <p> |
| Written callbacks are triggered exactly once, just after <em class="parameter"><code>im</code></em> has been |
| written to. |
| </p> |
| <p> |
| Written callbacks are a good place to do background writes to files. VIPS |
| uses them to implement (for example) writing to im_open("poop.jpg","w") |
| triggering a write to jpeg. |
| </p> |
| <p> |
| Evalend callbacks happen after a real write loop, whereas written is |
| triggered even for just attaching some callbacks to a "p" image. |
| </p> |
| <div class="variablelist"><table border="0"> |
| <col align="left" valign="top"> |
| <tbody> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>im</code></em> :</span></p></td> |
| <td>image to attach callback to |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>fn</code></em> :</span></p></td> |
| <td>callback function |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>a</code></em> :</span></p></td> |
| <td>user data 1 |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>b</code></em> :</span></p></td> |
| <td>user data 2 |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, or -1 on error. |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_add_evalstart_callback ()"> |
| <a name="im-add-evalstart-callback"></a><h3>im_add_evalstart_callback ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_add_evalstart_callback (<em class="parameter"><code><span class="type">IMAGE</span> *im</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-callback.html#im-callback-fn" title="im_callback_fn ()"><span class="type">im_callback_fn</span></a> fn</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *a</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *b</code></em>);</pre> |
| <p> |
| Attaches an eval start callback <em class="parameter"><code>fn</code></em> to <em class="parameter"><code>im</code></em>. |
| </p> |
| <p> |
| Eval start callbacks are called at the beginning of evaluation. They are a |
| good |
| place to get ready to give progress notification. |
| They can be called |
| many times. Every evalend call is guaranteed to have a matching evalstart, |
| but not necessarily any eval calls. |
| </p> |
| <p> |
| Eval callbacks are inherited. That is, any images which use your image |
| as input will inherit your eval callbacks. As a result, if you add an |
| eval callback to an image, you will be notified if any later image uses |
| your image for computation. |
| </p> |
| <p> |
| If a later image adds eval callbacks, then the inheritance is broken, |
| and that image will recieve notification instead. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-callback.html#im-add-eval-callback" title="im_add_eval_callback ()"><code class="function">im_add_eval_callback()</code></a>, <a class="link" href="libvips-callback.html#im-add-evalend-callback" title="im_add_evalend_callback ()"><code class="function">im_add_evalend_callback()</code></a>. |
| </p> |
| <div class="variablelist"><table border="0"> |
| <col align="left" valign="top"> |
| <tbody> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>im</code></em> :</span></p></td> |
| <td>image to attach callback to |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>fn</code></em> :</span></p></td> |
| <td>callback function |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>a</code></em> :</span></p></td> |
| <td>user data 1 |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>b</code></em> :</span></p></td> |
| <td>user data 2 |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, or -1 on error. |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_add_eval_callback ()"> |
| <a name="im-add-eval-callback"></a><h3>im_add_eval_callback ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_add_eval_callback (<em class="parameter"><code><span class="type">IMAGE</span> *im</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-callback.html#im-callback-fn" title="im_callback_fn ()"><span class="type">im_callback_fn</span></a> fn</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *a</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *b</code></em>);</pre> |
| <p> |
| Attaches an eval callback <em class="parameter"><code>fn</code></em> to <em class="parameter"><code>im</code></em>. |
| </p> |
| <p> |
| Eval callbacks are called during evaluation and are a good place to give |
| the user feedback about computation progress. In the eval callback, you may |
| look at the <a class="link" href="libvips-image.html#VipsProgress" title="VipsProgress"><span class="type">VipsProgress</span></a> <span class="type">time</span> member of <span class="type">IMAGE</span> to get information about |
| the number of |
| pels processed, elapsed time, and so on. |
| </p> |
| <p> |
| Eval callbacks are inherited. That is, any images which use your image |
| as input will inherit your eval callbacks. As a result, if you add an |
| eval callback to an image, you will be notified if any later image uses |
| your image for computation. |
| </p> |
| <p> |
| If a later image adds eval callbacks, then the inheritance is broken, |
| and that image will recieve notification instead. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-callback.html#im-add-evalend-callback" title="im_add_evalend_callback ()"><code class="function">im_add_evalend_callback()</code></a>, <a class="link" href="libvips-callback.html#im-add-evalstart-callback" title="im_add_evalstart_callback ()"><code class="function">im_add_evalstart_callback()</code></a>. |
| </p> |
| <div class="variablelist"><table border="0"> |
| <col align="left" valign="top"> |
| <tbody> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>im</code></em> :</span></p></td> |
| <td>image to attach callback to |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>fn</code></em> :</span></p></td> |
| <td>callback function |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>a</code></em> :</span></p></td> |
| <td>user data 1 |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>b</code></em> :</span></p></td> |
| <td>user data 2 |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, or -1 on error. |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_add_evalend_callback ()"> |
| <a name="im-add-evalend-callback"></a><h3>im_add_evalend_callback ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_add_evalend_callback (<em class="parameter"><code><span class="type">IMAGE</span> *im</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-callback.html#im-callback-fn" title="im_callback_fn ()"><span class="type">im_callback_fn</span></a> fn</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *a</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *b</code></em>);</pre> |
| <p> |
| Attaches an eval end callback <em class="parameter"><code>fn</code></em> to <em class="parameter"><code>im</code></em>. |
| </p> |
| <p> |
| Eval end callbacks are called at the end of evaluation. They are a good |
| place to clean up after progress notification or to display some |
| diagnostics about computation (eg. an overflow count). They can be called |
| many times. Every evalend call is guaranteed to have a matching evalstart, |
| but not necessarily any eval calls. |
| </p> |
| <p> |
| Eval callbacks are inherited. That is, any images which use your image |
| as input will inherit your eval callbacks. As a result, if you add an |
| eval callback to an image, you will be notified if any later image uses |
| your image for computation. |
| </p> |
| <p> |
| If a later image adds eval callbacks, then the inheritance is broken, |
| and that image will recieve notification instead. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-callback.html#im-add-eval-callback" title="im_add_eval_callback ()"><code class="function">im_add_eval_callback()</code></a>, <a class="link" href="libvips-callback.html#im-add-evalstart-callback" title="im_add_evalstart_callback ()"><code class="function">im_add_evalstart_callback()</code></a>. |
| </p> |
| <div class="variablelist"><table border="0"> |
| <col align="left" valign="top"> |
| <tbody> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>im</code></em> :</span></p></td> |
| <td>image to attach callback to |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>fn</code></em> :</span></p></td> |
| <td>callback function |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>a</code></em> :</span></p></td> |
| <td>user data 1 |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>b</code></em> :</span></p></td> |
| <td>user data 2 |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, or -1 on error. |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_add_invalidate_callback ()"> |
| <a name="im-add-invalidate-callback"></a><h3>im_add_invalidate_callback ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_add_invalidate_callback (<em class="parameter"><code><span class="type">IMAGE</span> *im</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-callback.html#im-callback-fn" title="im_callback_fn ()"><span class="type">im_callback_fn</span></a> fn</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *a</code></em>, |
| <em class="parameter"><code><span class="type">void</span> *b</code></em>);</pre> |
| <p> |
| Attaches an invalidate callback <em class="parameter"><code>fn</code></em> to <em class="parameter"><code>im</code></em>. |
| </p> |
| <p> |
| Invalidate callbacks are triggered |
| when VIPS invalidates the cache on an image. This is useful for |
| removing images from other, higher-level caches. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-image.html#im-invalidate" title="im_invalidate ()"><code class="function">im_invalidate()</code></a>. |
| </p> |
| <div class="variablelist"><table border="0"> |
| <col align="left" valign="top"> |
| <tbody> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>im</code></em> :</span></p></td> |
| <td>image to attach callback to |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>fn</code></em> :</span></p></td> |
| <td>callback function |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>a</code></em> :</span></p></td> |
| <td>user data 1 |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>b</code></em> :</span></p></td> |
| <td>user data 2 |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, or -1 on error. |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| </div> |
| <div class="refsect1" title="See Also"> |
| <a name="libvips-callback.see-also"></a><h2>See Also</h2> |
| <a class="link" href="libvips-image.html" title="image">image</a> |
| </div> |
| </div> |
| <div class="footer"> |
| <hr> |
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