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| <a href="#libvips-convolution.synopsis" class="shortcut">Top</a> |
| | |
| <a href="#libvips-convolution.description" class="shortcut">Description</a> |
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| <div class="refentry" title="convolution"> |
| <a name="libvips-convolution"></a><div class="titlepage"></div> |
| <div class="refnamediv"><table width="100%"><tr> |
| <td valign="top"> |
| <h2><span class="refentrytitle"><a name="libvips-convolution.top_of_page"></a>convolution</span></h2> |
| <p>convolution — convolve and correlate images</p> |
| </td> |
| <td valign="top" align="right"></td> |
| </tr></table></div> |
| <div class="refsect1" title="Stability Level"> |
| <a name="libvips-convolution.stability-level"></a><h2>Stability Level</h2> |
| Stable, unless otherwise indicated |
| </div> |
| <div class="refsynopsisdiv" title="Synopsis"> |
| <a name="libvips-convolution.synopsis"></a><h2>Synopsis</h2> |
| <pre class="synopsis"> |
| #include <vips/vips.h> |
| |
| <span class="returnvalue">int</span> <a class="link" href="libvips-convolution.html#im-conv" title="im_conv ()">im_conv</a> (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-mask.html#INTMASK:CAPS" title="INTMASK"><span class="type">INTMASK</span></a> *mask</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-convolution.html#im-conv-f" title="im_conv_f ()">im_conv_f</a> (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-mask.html#DOUBLEMASK:CAPS" title="DOUBLEMASK"><span class="type">DOUBLEMASK</span></a> *mask</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-convolution.html#im-convsep" title="im_convsep ()">im_convsep</a> (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-mask.html#INTMASK:CAPS" title="INTMASK"><span class="type">INTMASK</span></a> *mask</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-convolution.html#im-convsep-f" title="im_convsep_f ()">im_convsep_f</a> (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-mask.html#DOUBLEMASK:CAPS" title="DOUBLEMASK"><span class="type">DOUBLEMASK</span></a> *mask</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-convolution.html#im-compass" title="im_compass ()">im_compass</a> (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-mask.html#INTMASK:CAPS" title="INTMASK"><span class="type">INTMASK</span></a> *mask</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-convolution.html#im-gradient" title="im_gradient ()">im_gradient</a> (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-mask.html#INTMASK:CAPS" title="INTMASK"><span class="type">INTMASK</span></a> *mask</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-convolution.html#im-lindetect" title="im_lindetect ()">im_lindetect</a> (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-mask.html#INTMASK:CAPS" title="INTMASK"><span class="type">INTMASK</span></a> *mask</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-convolution.html#im-sharpen" title="im_sharpen ()">im_sharpen</a> (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><span class="type">int</span> mask_size</code></em>, |
| <em class="parameter"><code><span class="type">double</span> x1</code></em>, |
| <em class="parameter"><code><span class="type">double</span> y2</code></em>, |
| <em class="parameter"><code><span class="type">double</span> y3</code></em>, |
| <em class="parameter"><code><span class="type">double</span> m1</code></em>, |
| <em class="parameter"><code><span class="type">double</span> m2</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-convolution.html#im-grad-x" title="im_grad_x ()">im_grad_x</a> (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-convolution.html#im-grad-y" title="im_grad_y ()">im_grad_y</a> (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-convolution.html#im-fastcor" title="im_fastcor ()">im_fastcor</a> (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *ref</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-convolution.html#im-spcor" title="im_spcor ()">im_spcor</a> (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *ref</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-convolution.html#im-gradcor" title="im_gradcor ()">im_gradcor</a> (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *ref</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-convolution.html#im-contrast-surface" title="im_contrast_surface ()">im_contrast_surface</a> (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><span class="type">int</span> half_win_size</code></em>, |
| <em class="parameter"><code><span class="type">int</span> spacing</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-convolution.html#im-addgnoise" title="im_addgnoise ()">im_addgnoise</a> (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><span class="type">double</span> sigma</code></em>); |
| </pre> |
| </div> |
| <div class="refsect1" title="Description"> |
| <a name="libvips-convolution.description"></a><h2>Description</h2> |
| <p> |
| These operations convolve an image in some way, or are operations based on |
| simple convolution, or are useful with convolution. |
| </p> |
| </div> |
| <div class="refsect1" title="Details"> |
| <a name="libvips-convolution.details"></a><h2>Details</h2> |
| <div class="refsect2" title="im_conv ()"> |
| <a name="im-conv"></a><h3>im_conv ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_conv (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-mask.html#INTMASK:CAPS" title="INTMASK"><span class="type">INTMASK</span></a> *mask</code></em>);</pre> |
| <p> |
| Convolve <em class="parameter"><code>in</code></em> with <em class="parameter"><code>mask</code></em> using integer arithmetic. The output image |
| always has the same <a class="link" href="libvips-image.html#VipsBandFmt" title="enum VipsBandFmt"><span class="type">VipsBandFmt</span></a> as the input image. Non-complex images |
| only. |
| </p> |
| <p> |
| Each output pixel is |
| calculated as sigma[i]{pixel[i] * mask[i]} / scale + offset, where scale |
| and offset are part of <em class="parameter"><code>mask</code></em>. For integer <em class="parameter"><code>in</code></em>, the division by scale |
| includes round-to-nearest. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-convolution.html#im-conv-f" title="im_conv_f ()"><code class="function">im_conv_f()</code></a>, <a class="link" href="libvips-convolution.html#im-convsep" title="im_convsep ()"><code class="function">im_convsep()</code></a>, <a class="link" href="libvips-mask.html#im-create-imaskv" title="im_create_imaskv ()"><code class="function">im_create_imaskv()</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>in</code></em> :</span></p></td> |
| <td>input image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>out</code></em> :</span></p></td> |
| <td>output image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>mask</code></em> :</span></p></td> |
| <td>convolution mask |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, -1 on error |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_conv_f ()"> |
| <a name="im-conv-f"></a><h3>im_conv_f ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_conv_f (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-mask.html#DOUBLEMASK:CAPS" title="DOUBLEMASK"><span class="type">DOUBLEMASK</span></a> *mask</code></em>);</pre> |
| <p> |
| Convolve <em class="parameter"><code>in</code></em> with <em class="parameter"><code>mask</code></em> using floating-point arithmetic. The output image |
| is always <a class="link" href="libvips-image.html#IM-BANDFMT-FLOAT:CAPS"><code class="literal">IM_BANDFMT_FLOAT</code></a> unless <em class="parameter"><code>in</code></em> is <a class="link" href="libvips-image.html#IM-BANDFMT-DOUBLE:CAPS"><code class="literal">IM_BANDFMT_DOUBLE</code></a>, in which case |
| <em class="parameter"><code>out</code></em> is also <a class="link" href="libvips-image.html#IM-BANDFMT-DOUBLE:CAPS"><code class="literal">IM_BANDFMT_DOUBLE</code></a>. Non-complex images |
| only. |
| </p> |
| <p> |
| Each output pixel is |
| calculated as sigma[i]{pixel[i] * mask[i]} / scale + offset, where scale |
| and offset are part of <em class="parameter"><code>mask</code></em>. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-convolution.html#im-conv" title="im_conv ()"><code class="function">im_conv()</code></a>, <a class="link" href="libvips-convolution.html#im-convsep-f" title="im_convsep_f ()"><code class="function">im_convsep_f()</code></a>, <a class="link" href="libvips-mask.html#im-create-dmaskv" title="im_create_dmaskv ()"><code class="function">im_create_dmaskv()</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>in</code></em> :</span></p></td> |
| <td>input image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>out</code></em> :</span></p></td> |
| <td>output image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>mask</code></em> :</span></p></td> |
| <td>convolution mask |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, -1 on error |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_convsep ()"> |
| <a name="im-convsep"></a><h3>im_convsep ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_convsep (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-mask.html#INTMASK:CAPS" title="INTMASK"><span class="type">INTMASK</span></a> *mask</code></em>);</pre> |
| <p> |
| Perform a separable convolution of <em class="parameter"><code>in</code></em> with <em class="parameter"><code>mask</code></em> using integer arithmetic. |
| </p> |
| <p> |
| The mask must be 1xn or nx1 elements. |
| The output image |
| always has the same <a class="link" href="libvips-image.html#VipsBandFmt" title="enum VipsBandFmt"><span class="type">VipsBandFmt</span></a> as the input image. Non-complex images |
| only. |
| </p> |
| <p> |
| The image is convolved twice: once with <em class="parameter"><code>mask</code></em> and then again with <em class="parameter"><code>mask</code></em> |
| rotated by 90 degrees. This is much faster for certain types of mask |
| (gaussian blur, for example) than doing a full 2D convolution. |
| </p> |
| <p> |
| Each output pixel is |
| calculated as sigma[i]{pixel[i] * mask[i]} / scale + offset, where scale |
| and offset are part of <em class="parameter"><code>mask</code></em>. For integer <em class="parameter"><code>in</code></em>, the division by scale |
| includes round-to-nearest. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-convolution.html#im-convsep-f" title="im_convsep_f ()"><code class="function">im_convsep_f()</code></a>, <a class="link" href="libvips-convolution.html#im-conv" title="im_conv ()"><code class="function">im_conv()</code></a>, <a class="link" href="libvips-mask.html#im-create-imaskv" title="im_create_imaskv ()"><code class="function">im_create_imaskv()</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>in</code></em> :</span></p></td> |
| <td>input image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>out</code></em> :</span></p></td> |
| <td>output image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>mask</code></em> :</span></p></td> |
| <td>convolution mask |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, -1 on error |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_convsep_f ()"> |
| <a name="im-convsep-f"></a><h3>im_convsep_f ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_convsep_f (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-mask.html#DOUBLEMASK:CAPS" title="DOUBLEMASK"><span class="type">DOUBLEMASK</span></a> *mask</code></em>);</pre> |
| <p> |
| Perform a separable convolution of <em class="parameter"><code>in</code></em> with <em class="parameter"><code>mask</code></em> using floating-point |
| arithmetic. |
| </p> |
| <p> |
| The mask must be 1xn or nx1 elements. |
| The output image |
| is always <a class="link" href="libvips-image.html#IM-BANDFMT-FLOAT:CAPS"><code class="literal">IM_BANDFMT_FLOAT</code></a> unless <em class="parameter"><code>in</code></em> is <a class="link" href="libvips-image.html#IM-BANDFMT-DOUBLE:CAPS"><code class="literal">IM_BANDFMT_DOUBLE</code></a>, in which case |
| <em class="parameter"><code>out</code></em> is also <a class="link" href="libvips-image.html#IM-BANDFMT-DOUBLE:CAPS"><code class="literal">IM_BANDFMT_DOUBLE</code></a>. Non-complex images |
| only. |
| </p> |
| <p> |
| The image is convolved twice: once with <em class="parameter"><code>mask</code></em> and then again with <em class="parameter"><code>mask</code></em> |
| rotated by 90 degrees. This is much faster for certain types of mask |
| (gaussian blur, for example) than doing a full 2D convolution. |
| </p> |
| <p> |
| Each output pixel is |
| calculated as sigma[i]{pixel[i] * mask[i]} / scale + offset, where scale |
| and offset are part of <em class="parameter"><code>mask</code></em>. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-convolution.html#im-convsep" title="im_convsep ()"><code class="function">im_convsep()</code></a>, <a class="link" href="libvips-convolution.html#im-conv" title="im_conv ()"><code class="function">im_conv()</code></a>, <a class="link" href="libvips-mask.html#im-create-dmaskv" title="im_create_dmaskv ()"><code class="function">im_create_dmaskv()</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>in</code></em> :</span></p></td> |
| <td>input image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>out</code></em> :</span></p></td> |
| <td>output image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>mask</code></em> :</span></p></td> |
| <td>convolution mask |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, -1 on error |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_compass ()"> |
| <a name="im-compass"></a><h3>im_compass ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_compass (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-mask.html#INTMASK:CAPS" title="INTMASK"><span class="type">INTMASK</span></a> *mask</code></em>);</pre> |
| <p> |
| <em class="parameter"><code>in</code></em> is convolved 8 times with <em class="parameter"><code>mask</code></em>, each time <em class="parameter"><code>mask</code></em> is rotated by 45 |
| degrees. Each output pixel is the largest absolute value of the 8 |
| convolutions. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-convolution.html#im-lindetect" title="im_lindetect ()"><code class="function">im_lindetect()</code></a>, <a class="link" href="libvips-convolution.html#im-gradient" title="im_gradient ()"><code class="function">im_gradient()</code></a>, <a class="link" href="libvips-convolution.html#im-conv" title="im_conv ()"><code class="function">im_conv()</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>in</code></em> :</span></p></td> |
| <td>input image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>out</code></em> :</span></p></td> |
| <td>output image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>mask</code></em> :</span></p></td> |
| <td>convolution mask |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, -1 on error |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_gradient ()"> |
| <a name="im-gradient"></a><h3>im_gradient ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_gradient (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-mask.html#INTMASK:CAPS" title="INTMASK"><span class="type">INTMASK</span></a> *mask</code></em>);</pre> |
| <p> |
| <em class="parameter"><code>in</code></em> is convolved with <em class="parameter"><code>mask</code></em> and with <em class="parameter"><code>mask</code></em> after a 90 degree rotation. The |
| result is the sum of the absolute value of the two convolutions. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-convolution.html#im-lindetect" title="im_lindetect ()"><code class="function">im_lindetect()</code></a>, <a class="link" href="libvips-convolution.html#im-gradient" title="im_gradient ()"><code class="function">im_gradient()</code></a>, <a class="link" href="libvips-convolution.html#im-conv" title="im_conv ()"><code class="function">im_conv()</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>in</code></em> :</span></p></td> |
| <td>input image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>out</code></em> :</span></p></td> |
| <td>output image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>mask</code></em> :</span></p></td> |
| <td>convolution mask |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, -1 on error |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_lindetect ()"> |
| <a name="im-lindetect"></a><h3>im_lindetect ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_lindetect (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-mask.html#INTMASK:CAPS" title="INTMASK"><span class="type">INTMASK</span></a> *mask</code></em>);</pre> |
| <p> |
| <em class="parameter"><code>in</code></em> is convolved four times with <em class="parameter"><code>mask</code></em>, each time <em class="parameter"><code>mask</code></em> is rotated by 45 |
| degrees. Each output pixel is the largest absolute value of the four |
| convolutions. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-convolution.html#im-compass" title="im_compass ()"><code class="function">im_compass()</code></a>, <a class="link" href="libvips-convolution.html#im-gradient" title="im_gradient ()"><code class="function">im_gradient()</code></a>, <a class="link" href="libvips-convolution.html#im-conv" title="im_conv ()"><code class="function">im_conv()</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>in</code></em> :</span></p></td> |
| <td>input image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>out</code></em> :</span></p></td> |
| <td>output image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>mask</code></em> :</span></p></td> |
| <td>convolution mask |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, -1 on error |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_sharpen ()"> |
| <a name="im-sharpen"></a><h3>im_sharpen ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_sharpen (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><span class="type">int</span> mask_size</code></em>, |
| <em class="parameter"><code><span class="type">double</span> x1</code></em>, |
| <em class="parameter"><code><span class="type">double</span> y2</code></em>, |
| <em class="parameter"><code><span class="type">double</span> y3</code></em>, |
| <em class="parameter"><code><span class="type">double</span> m1</code></em>, |
| <em class="parameter"><code><span class="type">double</span> m2</code></em>);</pre> |
| <p> |
| Selectively sharpen the L channel of a LAB image. Works for <a class="link" href="libvips-image.html#IM-CODING-LABQ:CAPS"><code class="literal">IM_CODING_LABQ</code></a> |
| and LABS images. |
| </p> |
| <p> |
| The operation performs a gaussian blur of size <em class="parameter"><code>mask_size</code></em> and subtracts |
| from <em class="parameter"><code>in</code></em> to |
| generate a high-frequency signal. This signal is passed through a lookup |
| table formed from the five parameters and added back to <em class="parameter"><code>in</code></em>. |
| </p> |
| <p> |
| The lookup table is formed like this: |
| </p> |
| <p> |
| </p> |
| <div class="informalexample"><pre class="programlisting"> |
| ^ |
| y2 |- - - - - ----------- |
| | / |
| | / slope m2 |
| | .../ |
| -x1 | ... | |
| -------------------...----------------------> |
| | ... | x1 |
| |... slope m1 |
| / | |
| / m2 | |
| / | |
| / | |
| / | |
| / | |
| ______/ _ _ _ _ _ _ | -y3 |
| | |
| </pre></div> |
| <p> |
| </p> |
| <p> |
| For printing, we recommend the following settings: |
| </p> |
| <p> |
| </p> |
| <div class="informalexample"><pre class="programlisting"> |
| mask_size == 7 |
| x1 == 1.5 |
| y2 == 20 (don't brighten by more than 20 L*) |
| y3 == 50 (can darken by up to 50 L*) |
| |
| m1 == 1 (some sharpening in flat areas) |
| m2 == 2 (more sharpening in jaggy areas) |
| </pre></div> |
| <p> |
| </p> |
| <p> |
| If you want more or less sharpening, we suggest you just change the m1 |
| and m2 parameters. |
| </p> |
| <p> |
| The <em class="parameter"><code>mask_size</code></em> parameter changes the width of the fringe and can be |
| adjusted according to the output printing resolution. As an approximate |
| guideline, use 3 for 4 pixels/mm (CRT display resolution), 5 for 8 |
| pixels/mm, 7 for 12 pixels/mm and 9 for 16 pixels/mm (300 dpi == 12 |
| pixels/mm). These figures refer to the image raster, not the half-tone |
| resolution. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-convolution.html#im-conv" title="im_conv ()"><code class="function">im_conv()</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>in</code></em> :</span></p></td> |
| <td>input image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>out</code></em> :</span></p></td> |
| <td>output image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>mask_size</code></em> :</span></p></td> |
| <td>how large a mask to use |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>x1</code></em> :</span></p></td> |
| <td>flat/jaggy threshold |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>y2</code></em> :</span></p></td> |
| <td>maximum amount of brightening |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>y3</code></em> :</span></p></td> |
| <td>maximum amount of darkening |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>m1</code></em> :</span></p></td> |
| <td>slope for flat areas |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>m2</code></em> :</span></p></td> |
| <td>slope for jaggy areas |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, -1 on error. |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_grad_x ()"> |
| <a name="im-grad-x"></a><h3>im_grad_x ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_grad_x (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>);</pre> |
| <p> |
| Find horizontal differences between adjacent pixels. |
| </p> |
| <p> |
| Generates an image where the value of each pixel is the difference between |
| it and the pixel to its right. The output has the same height as the input |
| and one pixel less width. One-band integer formats only. The result is |
| always <a class="link" href="libvips-image.html#IM-BANDFMT-INT:CAPS"><code class="literal">IM_BANDFMT_INT</code></a>. |
| </p> |
| <p> |
| This operation is much faster than (though equivalent to) <a class="link" href="libvips-convolution.html#im-conv" title="im_conv ()"><code class="function">im_conv()</code></a> with the |
| mask [[-1, 1]]. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-convolution.html#im-grad-y" title="im_grad_y ()"><code class="function">im_grad_y()</code></a>, <a class="link" href="libvips-convolution.html#im-conv" title="im_conv ()"><code class="function">im_conv()</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>in</code></em> :</span></p></td> |
| <td>input image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>out</code></em> :</span></p></td> |
| <td>output image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, -1 on error |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_grad_y ()"> |
| <a name="im-grad-y"></a><h3>im_grad_y ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_grad_y (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>);</pre> |
| <p> |
| Find vertical differences between adjacent pixels. |
| </p> |
| <p> |
| Generates an image where the value of each pixel is the difference between |
| it and the pixel below it. The output has the same width as the input |
| and one pixel less height. One-band integer formats only. The result is |
| always <a class="link" href="libvips-image.html#IM-BANDFMT-INT:CAPS"><code class="literal">IM_BANDFMT_INT</code></a>. |
| </p> |
| <p> |
| This operation is much faster than (though equivalent to) <a class="link" href="libvips-convolution.html#im-conv" title="im_conv ()"><code class="function">im_conv()</code></a> with the |
| mask [[-1], [1]]. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-convolution.html#im-grad-x" title="im_grad_x ()"><code class="function">im_grad_x()</code></a>, <a class="link" href="libvips-convolution.html#im-conv" title="im_conv ()"><code class="function">im_conv()</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>in</code></em> :</span></p></td> |
| <td>input image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>out</code></em> :</span></p></td> |
| <td>output image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, -1 on error |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_fastcor ()"> |
| <a name="im-fastcor"></a><h3>im_fastcor ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_fastcor (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *ref</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>);</pre> |
| <p> |
| Calculate a fast correlation surface. |
| </p> |
| <p> |
| <em class="parameter"><code>ref</code></em> is placed at every position in <em class="parameter"><code>in</code></em> and the sum of squares of |
| differences calculated. One-band, 8-bit unsigned images only. The output |
| image is always <a class="link" href="libvips-image.html#IM-BANDFMT-UINT:CAPS"><code class="literal">IM_BANDFMT_UINT</code></a>. <em class="parameter"><code>ref</code></em> must be smaller than or equal to |
| <em class="parameter"><code>in</code></em>. The output |
| image is the same size as the input. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-convolution.html#im-spcor" title="im_spcor ()"><code class="function">im_spcor()</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>in</code></em> :</span></p></td> |
| <td>input image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>ref</code></em> :</span></p></td> |
| <td>reference image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>out</code></em> :</span></p></td> |
| <td>output image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, -1 on error |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_spcor ()"> |
| <a name="im-spcor"></a><h3>im_spcor ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_spcor (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *ref</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>);</pre> |
| <p> |
| Calculate a correlation surface. |
| </p> |
| <p> |
| <em class="parameter"><code>ref</code></em> is placed at every position in <em class="parameter"><code>in</code></em> and the correlation coefficient |
| calculated. One-band, 8 or 16-bit images only. <em class="parameter"><code>in</code></em> and <em class="parameter"><code>ref</code></em> must have the |
| same <a class="link" href="libvips-image.html#VipsBandFmt" title="enum VipsBandFmt"><span class="type">VipsBandFmt</span></a>. The output |
| image is always <a class="link" href="libvips-image.html#IM-BANDFMT-FLOAT:CAPS"><code class="literal">IM_BANDFMT_FLOAT</code></a>. <em class="parameter"><code>ref</code></em> must be smaller than or equal to |
| <em class="parameter"><code>in</code></em>. The output |
| image is the same size as the input. |
| </p> |
| <p> |
| The correlation coefficient is calculated as: |
| </p> |
| <p> |
| </p> |
| <div class="informalexample"><pre class="programlisting"> |
| sumij (ref(i,j)-mean(ref))(inkl(i,j)-mean(inkl)) |
| c(k,l) = ------------------------------------------------ |
| sqrt(sumij (ref(i,j)-mean(ref))^2) * |
| sqrt(sumij (inkl(i,j)-mean(inkl))^2) |
| </pre></div> |
| <p> |
| </p> |
| <p> |
| where inkl is the area of <em class="parameter"><code>in</code></em> centred at position (k,l). |
| </p> |
| <p> |
| from Niblack "An Introduction to Digital Image Processing", |
| Prentice/Hall, pp 138. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-convolution.html#im-gradcor" title="im_gradcor ()"><code class="function">im_gradcor()</code></a>, <a class="link" href="libvips-convolution.html#im-fastcor" title="im_fastcor ()"><code class="function">im_fastcor()</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>in</code></em> :</span></p></td> |
| <td>input image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>ref</code></em> :</span></p></td> |
| <td>reference image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>out</code></em> :</span></p></td> |
| <td>output image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, -1 on error |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_gradcor ()"> |
| <a name="im-gradcor"></a><h3>im_gradcor ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_gradcor (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *ref</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>);</pre> |
| <p> |
| Calculate a correlation surface. |
| </p> |
| <p> |
| <em class="parameter"><code>ref</code></em> is placed at every position in <em class="parameter"><code>in</code></em> and a correlation coefficient |
| calculated. One-band, integer images only. <em class="parameter"><code>in</code></em> and <em class="parameter"><code>ref</code></em> must have the |
| same <a class="link" href="libvips-image.html#VipsBandFmt" title="enum VipsBandFmt"><span class="type">VipsBandFmt</span></a>. The output |
| image is always <a class="link" href="libvips-image.html#IM-BANDFMT-FLOAT:CAPS"><code class="literal">IM_BANDFMT_FLOAT</code></a>. <em class="parameter"><code>ref</code></em> must be smaller than <em class="parameter"><code>in</code></em>. The output |
| image is the same size as the input. |
| </p> |
| <p> |
| The method takes the gradient images of the two images then takes the |
| dot-product correlation of the two vector images. |
| The vector expression of this method is my (tcv) own creation. It is |
| equivalent to the complex-number method of: |
| </p> |
| <p> |
| ARGYRIOU, V. et al. 2003. Estimation of sub-pixel motion using |
| gradient cross correlation. Electronics Letters, 39 (13). |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-convolution.html#im-spcor" title="im_spcor ()"><code class="function">im_spcor()</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>in</code></em> :</span></p></td> |
| <td>input image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>ref</code></em> :</span></p></td> |
| <td>reference image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>out</code></em> :</span></p></td> |
| <td>output image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, -1 on error |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_contrast_surface ()"> |
| <a name="im-contrast-surface"></a><h3>im_contrast_surface ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_contrast_surface (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><span class="type">int</span> half_win_size</code></em>, |
| <em class="parameter"><code><span class="type">int</span> spacing</code></em>);</pre> |
| <p> |
| Generate an image where the value of each pixel represents the |
| contrast within a window of half_win_size from the corresponsing |
| point in the input image. Sub-sample by a factor of spacing. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-convolution.html#im-spcor" title="im_spcor ()"><code class="function">im_spcor()</code></a>, <a class="link" href="libvips-convolution.html#im-gradcor" title="im_gradcor ()"><code class="function">im_gradcor()</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>in</code></em> :</span></p></td> |
| <td>input image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>out</code></em> :</span></p></td> |
| <td>output image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>half_win_size</code></em> :</span></p></td> |
| <td>window radius |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>spacing</code></em> :</span></p></td> |
| <td>subsample output by this |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, -1 on error. |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_addgnoise ()"> |
| <a name="im-addgnoise"></a><h3>im_addgnoise ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_addgnoise (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><span class="type">double</span> sigma</code></em>);</pre> |
| <p> |
| Add gaussian noise with mean 0 and variance sigma to <em class="parameter"><code>in</code></em>. |
| The noise is generated by averaging 12 random numbers, |
| see page 78, PIETGEN, 1989. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-conversion.html#im-gaussnoise" title="im_gaussnoise ()"><code class="function">im_gaussnoise()</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>in</code></em> :</span></p></td> |
| <td>input image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>out</code></em> :</span></p></td> |
| <td>output image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>sigma</code></em> :</span></p></td> |
| <td>standard deviation of noise |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><span class="emphasis"><em>Returns</em></span> :</span></p></td> |
| <td> 0 on success, -1 on error |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| </div> |
| </div> |
| <div class="footer"> |
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