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| <a href="#libvips-freq-filt.synopsis" class="shortcut">Top</a> |
| | |
| <a href="#libvips-freq-filt.description" class="shortcut">Description</a> |
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| </table> |
| <div class="refentry" title="freq_filt"> |
| <a name="libvips-freq-filt"></a><div class="titlepage"></div> |
| <div class="refnamediv"><table width="100%"><tr> |
| <td valign="top"> |
| <h2><span class="refentrytitle"><a name="libvips-freq-filt.top_of_page"></a>freq_filt</span></h2> |
| <p>freq_filt — fourier transforms and frequency-domin filters</p> |
| </td> |
| <td valign="top" align="right"></td> |
| </tr></table></div> |
| <div class="refsect1" title="Stability Level"> |
| <a name="libvips-freq-filt.stability-level"></a><h2>Stability Level</h2> |
| Stable, unless otherwise indicated |
| </div> |
| <div class="refsynopsisdiv" title="Synopsis"> |
| <a name="libvips-freq-filt.synopsis"></a><h2>Synopsis</h2> |
| <pre class="synopsis"> |
| #include <vips/vips.h> |
| |
| enum <a class="link" href="libvips-freq-filt.html#VipsMaskType" title="enum VipsMaskType">VipsMaskType</a>; |
| <span class="returnvalue">int</span> <a class="link" href="libvips-freq-filt.html#im-fwfft" title="im_fwfft ()">im_fwfft</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-freq-filt.html#im-invfft" title="im_invfft ()">im_invfft</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-freq-filt.html#im-invfftr" title="im_invfftr ()">im_invfftr</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-freq-filt.html#im-freqflt" title="im_freqflt ()">im_freqflt</a> (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *mask</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-freq-filt.html#im-disp-ps" title="im_disp_ps ()">im_disp_ps</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-freq-filt.html#im-rotquad" title="im_rotquad ()">im_rotquad</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-freq-filt.html#im-phasecor-fft" title="im_phasecor_fft ()">im_phasecor_fft</a> (<em class="parameter"><code><span class="type">IMAGE</span> *in1</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *in2</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-freq-filt.html#im-flt-image-freq" title="im_flt_image_freq ()">im_flt_image_freq</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-freq-filt.html#VipsMaskType" title="enum VipsMaskType"><span class="type">VipsMaskType</span></a> flag</code></em>, |
| <em class="parameter"><code>...</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-freq-filt.html#im-create-fmask" title="im_create_fmask ()">im_create_fmask</a> (<em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><span class="type">int</span> xsize</code></em>, |
| <em class="parameter"><code><span class="type">int</span> ysize</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-freq-filt.html#VipsMaskType" title="enum VipsMaskType"><span class="type">VipsMaskType</span></a> flag</code></em>, |
| <em class="parameter"><code>...</code></em>); |
| <span class="returnvalue">int</span> <a class="link" href="libvips-freq-filt.html#im-fractsurf" title="im_fractsurf ()">im_fractsurf</a> (<em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><span class="type">int</span> size</code></em>, |
| <em class="parameter"><code><span class="type">double</span> frd</code></em>); |
| </pre> |
| </div> |
| <div class="refsect1" title="Description"> |
| <a name="libvips-freq-filt.description"></a><h2>Description</h2> |
| <p> |
| To and from Fourier space, filter in Fourier space, convert Fourier-space |
| images to a displayable form. |
| </p> |
| </div> |
| <div class="refsect1" title="Details"> |
| <a name="libvips-freq-filt.details"></a><h2>Details</h2> |
| <div class="refsect2" title="enum VipsMaskType"> |
| <a name="VipsMaskType"></a><h3>enum VipsMaskType</h3> |
| <pre class="programlisting">typedef enum { |
| VIPS_MASK_IDEAL_HIGHPASS = 0, |
| VIPS_MASK_IDEAL_LOWPASS = 1, |
| VIPS_MASK_BUTTERWORTH_HIGHPASS = 2, |
| VIPS_MASK_BUTTERWORTH_LOWPASS = 3, |
| VIPS_MASK_GAUSS_HIGHPASS = 4, |
| VIPS_MASK_GAUSS_LOWPASS = 5, |
| |
| VIPS_MASK_IDEAL_RINGPASS = 6, |
| VIPS_MASK_IDEAL_RINGREJECT = 7, |
| VIPS_MASK_BUTTERWORTH_RINGPASS = 8, |
| VIPS_MASK_BUTTERWORTH_RINGREJECT = 9, |
| VIPS_MASK_GAUSS_RINGPASS = 10, |
| VIPS_MASK_GAUSS_RINGREJECT = 11, |
| |
| VIPS_MASK_IDEAL_BANDPASS = 12, |
| VIPS_MASK_IDEAL_BANDREJECT = 13, |
| VIPS_MASK_BUTTERWORTH_BANDPASS = 14, |
| VIPS_MASK_BUTTERWORTH_BANDREJECT = 15, |
| VIPS_MASK_GAUSS_BANDPASS = 16, |
| VIPS_MASK_GAUSS_BANDREJECT = 17, |
| |
| VIPS_MASK_FRACTAL_FLT = 18 |
| } VipsMaskType; |
| </pre> |
| </div> |
| <hr> |
| <div class="refsect2" title="im_fwfft ()"> |
| <a name="im-fwfft"></a><h3>im_fwfft ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_fwfft (<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> |
| Transform an image to Fourier space. |
| </p> |
| <p> |
| VIPS uses the fftw3 or fftw2 Fourier transform libraries if possible. If |
| they were not available when VIPS was built, it falls back to it's own |
| FFT functions which are slow and only work for square images whose sides |
| are a power of two. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-freq-filt.html#im-invfft" title="im_invfft ()"><code class="function">im_invfft()</code></a>, <a class="link" href="libvips-freq-filt.html#im-disp-ps" title="im_disp_ps ()"><code class="function">im_disp_ps()</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_invfft ()"> |
| <a name="im-invfft"></a><h3>im_invfft ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_invfft (<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> |
| Transform an image from Fourier space to real space. The result is complex. |
| If you are OK with a real result, use <a class="link" href="libvips-freq-filt.html#im-invfftr" title="im_invfftr ()"><code class="function">im_invfftr()</code></a> instead, it's quicker. |
| </p> |
| <p> |
| VIPS uses the fftw3 or fftw2 Fourier transform libraries if possible. If |
| they were not available when VIPS was built, it falls back to it's own |
| FFT functions which are slow and only work for square images whose sides |
| are a power of two. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-freq-filt.html#im-invfftr" title="im_invfftr ()"><code class="function">im_invfftr()</code></a>, <a class="link" href="libvips-freq-filt.html#im-fwfft" title="im_fwfft ()"><code class="function">im_fwfft()</code></a>, <a class="link" href="libvips-freq-filt.html#im-disp-ps" title="im_disp_ps ()"><code class="function">im_disp_ps()</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_invfftr ()"> |
| <a name="im-invfftr"></a><h3>im_invfftr ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_invfftr (<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> |
| Transform an image from Fourier space to real space, giving a real result. |
| This is faster than <a class="link" href="libvips-freq-filt.html#im-invfft" title="im_invfft ()"><code class="function">im_invfft()</code></a>, which gives a complex result. |
| </p> |
| <p> |
| VIPS uses the fftw3 or fftw2 Fourier transform libraries if possible. If |
| they were not available when VIPS was built, it falls back to it's own |
| FFT functions which are slow and only work for square images whose sides |
| are a power of two. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-freq-filt.html#im-invfft" title="im_invfft ()"><code class="function">im_invfft()</code></a>, <a class="link" href="libvips-freq-filt.html#im-fwfft" title="im_fwfft ()"><code class="function">im_fwfft()</code></a>, <a class="link" href="libvips-freq-filt.html#im-disp-ps" title="im_disp_ps ()"><code class="function">im_disp_ps()</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_freqflt ()"> |
| <a name="im-freqflt"></a><h3>im_freqflt ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_freqflt (<em class="parameter"><code><span class="type">IMAGE</span> *in</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *mask</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>);</pre> |
| <p> |
| Filter an image in Fourier space. |
| </p> |
| <p> |
| <em class="parameter"><code>in</code></em> is transformed to Fourier space, multipled with the mask image, then |
| transformed back to real space. If <em class="parameter"><code>in</code></em> is already a complex image, just |
| multiply then inverse transform. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-freq-filt.html#im-invfftr" title="im_invfftr ()"><code class="function">im_invfftr()</code></a>, <a class="link" href="libvips-freq-filt.html#im-create-fmask" title="im_create_fmask ()"><code class="function">im_create_fmask()</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>mask</code></em> :</span></p></td> |
| <td>mask 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_disp_ps ()"> |
| <a name="im-disp-ps"></a><h3>im_disp_ps ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_disp_ps (<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> |
| Make a displayable (ie. 8-bit unsigned int) power spectrum. |
| </p> |
| <p> |
| If <em class="parameter"><code>in</code></em> is non-complex, it is transformed to Fourier space. Then the |
| absolute value is passed through <a class="link" href="libvips-conversion.html#im-scaleps" title="im_scaleps ()"><code class="function">im_scaleps()</code></a>, and <a class="link" href="libvips-freq-filt.html#im-rotquad" title="im_rotquad ()"><code class="function">im_rotquad()</code></a>. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-conversion.html#im-scaleps" title="im_scaleps ()"><code class="function">im_scaleps()</code></a>, <a class="link" href="libvips-freq-filt.html#im-rotquad" title="im_rotquad ()"><code class="function">im_rotquad()</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_rotquad ()"> |
| <a name="im-rotquad"></a><h3>im_rotquad ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_rotquad (<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> |
| Rotate the quadrants of the image so that the point that was at the |
| top-left is now in the centre. Handy for moving Fourier images to optical |
| space. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-conversion.html#im-wrap" title="im_wrap ()"><code class="function">im_wrap()</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_phasecor_fft ()"> |
| <a name="im-phasecor-fft"></a><h3>im_phasecor_fft ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_phasecor_fft (<em class="parameter"><code><span class="type">IMAGE</span> *in1</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *in2</code></em>, |
| <em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>);</pre> |
| <p> |
| Convert the two input images to Fourier space, calculate phase-correlation, |
| back to real space. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-freq-filt.html#im-fwfft" title="im_fwfft ()"><code class="function">im_fwfft()</code></a>, <a class="link" href="libvips-arithmetic.html#im-cross-phase" title="im_cross_phase ()"><code class="function">im_cross_phase()</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>in1</code></em> :</span></p></td> |
| <td>first input image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>in2</code></em> :</span></p></td> |
| <td>second 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_flt_image_freq ()"> |
| <a name="im-flt-image-freq"></a><h3>im_flt_image_freq ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_flt_image_freq (<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-freq-filt.html#VipsMaskType" title="enum VipsMaskType"><span class="type">VipsMaskType</span></a> flag</code></em>, |
| <em class="parameter"><code>...</code></em>);</pre> |
| <p> |
| Creates a mask (see <a class="link" href="libvips-freq-filt.html#im-create-fmask" title="im_create_fmask ()"><code class="function">im_create_fmask()</code></a>) and filters an image with it (see |
| <a class="link" href="libvips-freq-filt.html#im-freqflt" title="im_freqflt ()"><code class="function">im_freqflt()</code></a>). |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-freq-filt.html#im-create-fmask" title="im_create_fmask ()"><code class="function">im_create_fmask()</code></a>, <a class="link" href="libvips-freq-filt.html#im-freqflt" title="im_freqflt ()"><code class="function">im_freqflt()</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>flag</code></em> :</span></p></td> |
| <td>mask type |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>...</code></em> :</span></p></td> |
| <td>mask parameters |
| </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_create_fmask ()"> |
| <a name="im-create-fmask"></a><h3>im_create_fmask ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_create_fmask (<em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><span class="type">int</span> xsize</code></em>, |
| <em class="parameter"><code><span class="type">int</span> ysize</code></em>, |
| <em class="parameter"><code><a class="link" href="libvips-freq-filt.html#VipsMaskType" title="enum VipsMaskType"><span class="type">VipsMaskType</span></a> flag</code></em>, |
| <em class="parameter"><code>...</code></em>);</pre> |
| <p> |
| This operation creates a one-band float image of the specified size. The |
| image must be square, and the sides must be a power of two. The image has |
| values in the range [0, 1] and is typically used for multiplying against |
| frequency domain images to filter them. |
| </p> |
| <p> |
| All masks are created with the DC component at (0, 0), so you might want to |
| rotate the quadrants with <a class="link" href="libvips-freq-filt.html#im-rotquad" title="im_rotquad ()"><code class="function">im_rotquad()</code></a> before viewing. The DC pixel always |
| has the value 1.0. |
| </p> |
| <p> |
| The value of <em class="parameter"><code>flag</code></em> sets the type pf mask created, and extra parameters set |
| the exact mask shape. All extra parameters are doubles. This table |
| summarises the possible values: |
| </p> |
| <p> |
| </p> |
| <div class="table"> |
| <a name="id517714"></a><p class="title"><b>Table 6. Parameters for <a class="link" href="libvips-freq-filt.html#im-create-fmask" title="im_create_fmask ()"><code class="function">im_create_fmask()</code></a></b></p> |
| <div class="table-contents"><table summary="Parameters for im_create_fmask()" border="1"> |
| <colgroup> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th align="left"><a class="link" href="libvips-freq-filt.html#VipsMaskType" title="enum VipsMaskType"><span class="type">VipsMaskType</span></a></th> |
| <th align="left">nargs</th> |
| <th align="left">Parameters (all double)</th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td align="left"><span class="type">VIPS_MASK_IDEAL_HIGHPASS</span></td> |
| <td align="left">1</td> |
| <td align="left">frequency_cutoff</td> |
| </tr> |
| <tr> |
| <td align="left"><span class="type">VIPS_MASK_IDEAL_LOWPASS</span></td> |
| <td align="left">1</td> |
| <td align="left">frequency_cutoff</td> |
| </tr> |
| <tr> |
| <td align="left"><span class="type">VIPS_MASK_BUTTERWORTH_HIGHPASS</span></td> |
| <td align="left">3</td> |
| <td align="left">order, frequency_cutoff, amplitude_cutoff</td> |
| </tr> |
| <tr> |
| <td align="left"><span class="type">VIPS_MASK_BUTTERWORTH_LOWPASS</span></td> |
| <td align="left">3</td> |
| <td align="left">order, frequency_cutoff, amplitude_cutoff</td> |
| </tr> |
| <tr> |
| <td align="left"><span class="type">VIPS_MASK_GAUSS_HIGHPASS</span></td> |
| <td align="left">2</td> |
| <td align="left">frequency_cutoff, amplitude_cutoff</td> |
| </tr> |
| <tr> |
| <td align="left"><span class="type">VIPS_MASK_GAUSS_LOWPASS</span></td> |
| <td align="left">2</td> |
| <td align="left">frequency_cutoff, amplitude_cutoff</td> |
| </tr> |
| <tr> |
| <td align="left"><span class="type">VIPS_MASK_IDEAL_RINGPASS</span></td> |
| <td align="left">2</td> |
| <td align="left">frequency_cutoff, width</td> |
| </tr> |
| <tr> |
| <td align="left"><span class="type">VIPS_MASK_IDEAL_RINGREJECT</span></td> |
| <td align="left">2</td> |
| <td align="left">frequency_cutoff, width</td> |
| </tr> |
| <tr> |
| <td align="left"><span class="type">VIPS_MASK_BUTTERWORTH_RINGPASS</span></td> |
| <td align="left">4</td> |
| <td align="left">order, frequency_cutoff, width, amplitude_cutoff</td> |
| </tr> |
| <tr> |
| <td align="left"><span class="type">VIPS_MASK_BUTTERWORTH_RINGREJECT</span></td> |
| <td align="left">4</td> |
| <td align="left">order, frequency_cutoff, width, amplitude_cutoff</td> |
| </tr> |
| <tr> |
| <td align="left"><span class="type">VIPS_MASK_GAUSS_RINGPASS</span></td> |
| <td align="left">3</td> |
| <td align="left">frequency_cutoff, width, amplitude_cutoff</td> |
| </tr> |
| <tr> |
| <td align="left"><span class="type">VIPS_MASK_GAUSS_RINGREJECT</span></td> |
| <td align="left">3</td> |
| <td align="left">frequency_cutoff, width, amplitude_cutoff</td> |
| </tr> |
| <tr> |
| <td align="left"><span class="type">VIPS_MASK_IDEAL_BANDPASS</span></td> |
| <td align="left">3</td> |
| <td align="left">frequency_cutoffx, frequency_cutoffy, radius</td> |
| </tr> |
| <tr> |
| <td align="left"><span class="type">VIPS_MASK_IDEAL_BANDREJECT</span></td> |
| <td align="left">3</td> |
| <td align="left">frequency_cutoffx, frequency_cutoffy, radius</td> |
| </tr> |
| <tr> |
| <td align="left"><span class="type">VIPS_MASK_BUTTERWORTH_BANDPASS</span></td> |
| <td align="left">5</td> |
| <td align="left">order, frequency_cutoffx, frequency_cutoffy, radius, |
| amplitude_cutoff</td> |
| </tr> |
| <tr> |
| <td align="left"><span class="type">VIPS_MASK_BUTTERWORTH_BANDREJECT</span></td> |
| <td align="left">5</td> |
| <td align="left">order, frequency_cutoffx, frequency_cutoffy, radius, |
| amplitude_cutoff</td> |
| </tr> |
| <tr> |
| <td align="left"><span class="type">VIPS_MASK_GAUSS_BANDPASS</span></td> |
| <td align="left">4</td> |
| <td align="left">frequency_cutoffx, frequency_cutoffy, radius, |
| amplitude_cutoff</td> |
| </tr> |
| <tr> |
| <td align="left"><span class="type">VIPS_MASK_GAUSS_BANDREJECT</span></td> |
| <td align="left">4</td> |
| <td align="left">frequency_cutoffx, frequency_cutoffy, radius, |
| amplitude_cutoff</td> |
| </tr> |
| <tr> |
| <td align="left"><span class="type">VIPS_MASK_FRACTAL_FLT</span></td> |
| <td align="left">1</td> |
| <td align="left">fractal_dimension</td> |
| </tr> |
| </tbody> |
| </table></div> |
| </div> |
| <p><br class="table-break"> |
| </p> |
| <p> |
| Unless noted below, all parameters are expressed as percentages, scaled to |
| [0, 1]. |
| </p> |
| <p> |
| <span class="emphasis"><em>High-pass, low-pass masks:</em></span> A high pass filter |
| mask filters the low frequencies while allowing the high frequencies to |
| get through. The reverse happens with a low pass filter mask. |
| </p> |
| <p> |
| <span class="emphasis"><em>Ring-pass, ring-reject masks:</em></span> A ring filter passes or |
| rejects a range of frequencies. The range is specified by the |
| <em class="parameter"><code>frequency_cutoff</code></em> and the <em class="parameter"><code>width</code></em>. |
| </p> |
| <p> |
| <span class="emphasis"><em>Band-pass, band-reject masks:</em></span> These masks are used to |
| pass or remove spatial frequencies around a given frequency. The position |
| of the frequency to pass or remove is given by <em class="parameter"><code>frequency_cutoffx</code></em> and |
| <em class="parameter"><code>frequency_cutoffy</code></em>. The size of the region around the point is given by |
| <em class="parameter"><code>radius</code></em>. |
| </p> |
| <p> |
| <span class="emphasis"><em>Ideal filters:</em></span> These filters pass or reject |
| frequencies with a sharp cutoff at the transition. |
| </p> |
| <p> |
| <span class="emphasis"><em>Butterworth filters:</em></span> These filters use a Butterworth |
| function to separate the frequencies (see Gonzalez and Wintz, Digital |
| Image Processing, 1987). The shape of the curve is controlled by <em class="parameter"><code>order</code></em>: |
| higher values give a sharper transition. |
| </p> |
| <p> |
| <span class="emphasis"><em>Gaussian filters:</em></span> These filters have a smooth Gaussian |
| shape, controlled by <em class="parameter"><code>amplitude_cutoff</code></em>. |
| </p> |
| <p> |
| <span class="emphasis"><em>VIPS_MASK_FRACTAL_FLT:</em></span> This mask is handy for |
| filtering images of gaussian noise in order to create surfaces of a given |
| fractal dimension. <em class="parameter"><code>fractal_dimension</code></em> should be between 2 and 3. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-freq-filt.html#im-flt-image-freq" title="im_flt_image_freq ()"><code class="function">im_flt_image_freq()</code></a>, <a class="link" href="libvips-freq-filt.html#im-rotquad" title="im_rotquad ()"><code class="function">im_rotquad()</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>out</code></em> :</span></p></td> |
| <td>image to write to |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>xsize</code></em> :</span></p></td> |
| <td>image size |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>ysize</code></em> :</span></p></td> |
| <td>image size |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>flag</code></em> :</span></p></td> |
| <td>mask type |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>...</code></em> :</span></p></td> |
| <td>mask parameters |
| </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_fractsurf ()"> |
| <a name="im-fractsurf"></a><h3>im_fractsurf ()</h3> |
| <pre class="programlisting"><span class="returnvalue">int</span> im_fractsurf (<em class="parameter"><code><span class="type">IMAGE</span> *out</code></em>, |
| <em class="parameter"><code><span class="type">int</span> size</code></em>, |
| <em class="parameter"><code><span class="type">double</span> frd</code></em>);</pre> |
| <p> |
| Generate an image of size <em class="parameter"><code>size</code></em> and fractal dimension <em class="parameter"><code>frd</code></em>. The dimension |
| should be between 2 and 3. |
| </p> |
| <p> |
| See also: <a class="link" href="libvips-conversion.html#im-gaussnoise" title="im_gaussnoise ()"><code class="function">im_gaussnoise()</code></a>, <a class="link" href="libvips-freq-filt.html#im-flt-image-freq" title="im_flt_image_freq ()"><code class="function">im_flt_image_freq()</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>out</code></em> :</span></p></td> |
| <td>output image |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>size</code></em> :</span></p></td> |
| <td>size of image to generate |
| </td> |
| </tr> |
| <tr> |
| <td><p><span class="term"><em class="parameter"><code>frd</code></em> :</span></p></td> |
| <td>fractal dimension |
| </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 class="refsect1" title="See Also"> |
| <a name="libvips-freq-filt.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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