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   5 <title>CMSIS DSP Software Library: Bilinear Interpolation</title>
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  43 <div class="header">
  44   <div class="summary">
  45 <a href="#func-members">Functions</a>  </div>
  46   <div class="headertitle">
  47 <h1>Bilinear Interpolation<br/>
  48 <small>
  49 [<a class="el" href="group__group_interpolation.html">Interpolation Functions</a>]</small>
  50 </h1>  </div>
  51 </div>
  52 <div class="contents">
  53 <table class="memberdecls">
  54 <tr><td colspan="2"><h2><a name="func-members"></a>
  55 Functions</h2></td></tr>
  56 <tr><td class="memItemLeft" align="right" valign="top">static __INLINE <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group___bilinear_interpolate.html#gab49a4c0f64854903d996d01ba38f711a">arm_bilinear_interp_f32</a> (const <a class="el" href="structarm__bilinear__interp__instance__f32.html">arm_bilinear_interp_instance_f32</a> *S, <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> X, <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> Y)</td></tr>
  57 <tr><td class="memItemLeft" align="right" valign="top">static __INLINE <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group___bilinear_interpolate.html#ga202a033c8a2ad3678b136f93153b6d13">arm_bilinear_interp_q31</a> (<a class="el" href="structarm__bilinear__interp__instance__q31.html">arm_bilinear_interp_instance_q31</a> *S, <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> X, <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> Y)</td></tr>
  58 <tr><td class="memItemLeft" align="right" valign="top">static __INLINE <a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group___bilinear_interpolate.html#gaa8dffbc2a01bb7accf231384498ec85e">arm_bilinear_interp_q15</a> (<a class="el" href="structarm__bilinear__interp__instance__q15.html">arm_bilinear_interp_instance_q15</a> *S, <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> X, <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> Y)</td></tr>
  59 <tr><td class="memItemLeft" align="right" valign="top">static __INLINE <a class="el" href="arm__math_8h.html#ae541b6f232c305361e9b416fc9eed263">q7_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="group___bilinear_interpolate.html#gade8db9706a3ae9ad03b2750a239d2ee6">arm_bilinear_interp_q7</a> (<a class="el" href="structarm__bilinear__interp__instance__q7.html">arm_bilinear_interp_instance_q7</a> *S, <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> X, <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> Y)</td></tr>
  60 </table>
  61 <hr/><a name="_details"></a><h2>Detailed Description</h2>
  62 <p>Bilinear interpolation is an extension of linear interpolation applied to a two dimensional grid. The underlying function <code>f(x, y)</code> is sampled on a regular grid and the interpolation process determines values between the grid points. Bilinear interpolation is equivalent to two step linear interpolation, first in the x-dimension and then in the y-dimension. Bilinear interpolation is often used in image processing to rescale images. The CMSIS DSP library provides bilinear interpolation functions for Q7, Q15, Q31, and floating-point data types.</p>
  63 <p><b>Algorithm</b> </p>
  64 <dl class="user"><dt><b></b></dt><dd>The instance structure used by the bilinear interpolation functions describes a two dimensional data table. For floating-point, the instance structure is defined as: <pre>
  65    typedef struct
  66    {
  67      uint16_t numRows;
  68      uint16_t numCols;
  69      float32_t *pData;
  70  } <a class="el" href="structarm__bilinear__interp__instance__f32.html" title="Instance structure for the floating-point bilinear interpolation function.">arm_bilinear_interp_instance_f32</a>;
  71  </pre></dd></dl>
  72 <dl class="user"><dt><b></b></dt><dd>where <code>numRows</code> specifies the number of rows in the table; <code>numCols</code> specifies the number of columns in the table; and <code>pData</code> points to an array of size <code>numRows*numCols</code> values. The data table <code>pTable</code> is organized in row order and the supplied data values fall on integer indexes. That is, table element (x,y) is located at <code>pTable[x + y*numCols]</code> where x and y are integers.</dd></dl>
  73 <dl class="user"><dt><b></b></dt><dd>Let <code>(x, y)</code> specify the desired interpolation point. Then define: <pre>
  74      XF = floor(x)
  75      YF = floor(y)
  76  </pre> </dd></dl>
  77 <dl class="user"><dt><b></b></dt><dd>The interpolated output point is computed as: <pre>
  78   f(x, y) = f(XF, YF) * (1-(x-XF)) * (1-(y-YF))
  79            + f(XF+1, YF) * (x-XF)*(1-(y-YF))
  80            + f(XF, YF+1) * (1-(x-XF))*(y-YF)
  81            + f(XF+1, YF+1) * (x-XF)*(y-YF)
  82  </pre> Note that the coordinates (x, y) contain integer and fractional components. The integer components specify which portion of the table to use while the fractional components control the interpolation processor.</dd></dl>
  83 <dl class="user"><dt><b></b></dt><dd>if (x,y) are outside of the table boundary, Bilinear interpolation returns zero output. </dd></dl>
  84 <hr/><h2>Function Documentation</h2>
  85 <a class="anchor" id="gab49a4c0f64854903d996d01ba38f711a"></a><!-- doxytag: member="arm_math.h::arm_bilinear_interp_f32" ref="gab49a4c0f64854903d996d01ba38f711a" args="(const arm_bilinear_interp_instance_f32 *S, float32_t X, float32_t Y)" -->
  86 <div class="memitem">
  87 <div class="memproto">
  88       <table class="memname">
  89         <tr>
  90           <td class="memname">static __INLINE <a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a> arm_bilinear_interp_f32 </td>
  91           <td>(</td>
  92           <td class="paramtype">const <a class="el" href="structarm__bilinear__interp__instance__f32.html">arm_bilinear_interp_instance_f32</a> *&#160;</td>
  93           <td class="paramname"> <em>S</em>, </td>
  94         </tr>
  95         <tr>
  96           <td class="paramkey"></td>
  97           <td></td>
  98           <td class="paramtype"><a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a>&#160;</td>
  99           <td class="paramname"> <em>X</em>, </td>
 100         </tr>
 101         <tr>
 102           <td class="paramkey"></td>
 103           <td></td>
 104           <td class="paramtype"><a class="el" href="arm__math_8h.html#a4611b605e45ab401f02cab15c5e38715">float32_t</a>&#160;</td>
 105           <td class="paramname"> <em>Y</em>&#160;</td>
 106         </tr>
 107         <tr>
 108           <td></td>
 109           <td>)</td>
 110           <td></td><td><code> [static]</code></td>
 111         </tr>
 112       </table>
 113 </div>
 114 <div class="memdoc">
 115
 116 <p>Floating-point bilinear interpolation. </p>
 117 <dl><dt><b>Parameters:</b></dt><dd>
 118   <table class="params">
 119     <tr><td class="paramdir">[in,out]</td><td class="paramname">*S</td><td>points to an instance of the interpolation structure. </td></tr>
 120     <tr><td class="paramdir">[in]</td><td class="paramname">X</td><td>interpolation coordinate. </td></tr>
 121     <tr><td class="paramdir">[in]</td><td class="paramname">Y</td><td>interpolation coordinate. </td></tr>
 122   </table>
 123   </dd>
 124 </dl>
 125 <dl class="return"><dt><b>Returns:</b></dt><dd>out interpolated value. </dd></dl>
 126
 127 <p>Definition at line <a class="el" href="arm__math_8h_source.html#l06739">6739</a> of file <a class="el" href="arm__math_8h_source.html">arm_math.h</a>.</p>
 128
 129 </div>
 130 </div>
 131 <a class="anchor" id="ga202a033c8a2ad3678b136f93153b6d13"></a><!-- doxytag: member="arm_math.h::arm_bilinear_interp_q31" ref="ga202a033c8a2ad3678b136f93153b6d13" args="(arm_bilinear_interp_instance_q31 *S, q31_t X, q31_t Y)" -->
 132 <div class="memitem">
 133 <div class="memproto">
 134       <table class="memname">
 135         <tr>
 136           <td class="memname">static __INLINE <a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a> arm_bilinear_interp_q31 </td>
 137           <td>(</td>
 138           <td class="paramtype"><a class="el" href="structarm__bilinear__interp__instance__q31.html">arm_bilinear_interp_instance_q31</a> *&#160;</td>
 139           <td class="paramname"> <em>S</em>, </td>
 140         </tr>
 141         <tr>
 142           <td class="paramkey"></td>
 143           <td></td>
 144           <td class="paramtype"><a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a>&#160;</td>
 145           <td class="paramname"> <em>X</em>, </td>
 146         </tr>
 147         <tr>
 148           <td class="paramkey"></td>
 149           <td></td>
 150           <td class="paramtype"><a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a>&#160;</td>
 151           <td class="paramname"> <em>Y</em>&#160;</td>
 152         </tr>
 153         <tr>
 154           <td></td>
 155           <td>)</td>
 156           <td></td><td><code> [static]</code></td>
 157         </tr>
 158       </table>
 159 </div>
 160 <div class="memdoc">
 161
 162 <p>Q31 bilinear interpolation. </p>
 163 <dl><dt><b>Parameters:</b></dt><dd>
 164   <table class="params">
 165     <tr><td class="paramdir">[in,out]</td><td class="paramname">*S</td><td>points to an instance of the interpolation structure. </td></tr>
 166     <tr><td class="paramdir">[in]</td><td class="paramname">X</td><td>interpolation coordinate in 12.20 format. </td></tr>
 167     <tr><td class="paramdir">[in]</td><td class="paramname">Y</td><td>interpolation coordinate in 12.20 format. </td></tr>
 168   </table>
 169   </dd>
 170 </dl>
 171 <dl class="return"><dt><b>Returns:</b></dt><dd>out interpolated value. </dd></dl>
 172
 173 <p>Definition at line <a class="el" href="arm__math_8h_source.html#l06806">6806</a> of file <a class="el" href="arm__math_8h_source.html">arm_math.h</a>.</p>
 174
 175 </div>
 176 </div>
 177 <a class="anchor" id="gaa8dffbc2a01bb7accf231384498ec85e"></a><!-- doxytag: member="arm_math.h::arm_bilinear_interp_q15" ref="gaa8dffbc2a01bb7accf231384498ec85e" args="(arm_bilinear_interp_instance_q15 *S, q31_t X, q31_t Y)" -->
 178 <div class="memitem">
 179 <div class="memproto">
 180       <table class="memname">
 181         <tr>
 182           <td class="memname">static __INLINE <a class="el" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea">q15_t</a> arm_bilinear_interp_q15 </td>
 183           <td>(</td>
 184           <td class="paramtype"><a class="el" href="structarm__bilinear__interp__instance__q15.html">arm_bilinear_interp_instance_q15</a> *&#160;</td>
 185           <td class="paramname"> <em>S</em>, </td>
 186         </tr>
 187         <tr>
 188           <td class="paramkey"></td>
 189           <td></td>
 190           <td class="paramtype"><a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a>&#160;</td>
 191           <td class="paramname"> <em>X</em>, </td>
 192         </tr>
 193         <tr>
 194           <td class="paramkey"></td>
 195           <td></td>
 196           <td class="paramtype"><a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a>&#160;</td>
 197           <td class="paramname"> <em>Y</em>&#160;</td>
 198         </tr>
 199         <tr>
 200           <td></td>
 201           <td>)</td>
 202           <td></td><td><code> [static]</code></td>
 203         </tr>
 204       </table>
 205 </div>
 206 <div class="memdoc">
 207
 208 <p>Q15 bilinear interpolation. </p>
 209 <dl><dt><b>Parameters:</b></dt><dd>
 210   <table class="params">
 211     <tr><td class="paramdir">[in,out]</td><td class="paramname">*S</td><td>points to an instance of the interpolation structure. </td></tr>
 212     <tr><td class="paramdir">[in]</td><td class="paramname">X</td><td>interpolation coordinate in 12.20 format. </td></tr>
 213     <tr><td class="paramdir">[in]</td><td class="paramname">Y</td><td>interpolation coordinate in 12.20 format. </td></tr>
 214   </table>
 215   </dd>
 216 </dl>
 217 <dl class="return"><dt><b>Returns:</b></dt><dd>out interpolated value. </dd></dl>
 218
 219 <p>Definition at line <a class="el" href="arm__math_8h_source.html#l06882">6882</a> of file <a class="el" href="arm__math_8h_source.html">arm_math.h</a>.</p>
 220
 221 </div>
 222 </div>
 223 <a class="anchor" id="gade8db9706a3ae9ad03b2750a239d2ee6"></a><!-- doxytag: member="arm_math.h::arm_bilinear_interp_q7" ref="gade8db9706a3ae9ad03b2750a239d2ee6" args="(arm_bilinear_interp_instance_q7 *S, q31_t X, q31_t Y)" -->
 224 <div class="memitem">
 225 <div class="memproto">
 226       <table class="memname">
 227         <tr>
 228           <td class="memname">static __INLINE <a class="el" href="arm__math_8h.html#ae541b6f232c305361e9b416fc9eed263">q7_t</a> arm_bilinear_interp_q7 </td>
 229           <td>(</td>
 230           <td class="paramtype"><a class="el" href="structarm__bilinear__interp__instance__q7.html">arm_bilinear_interp_instance_q7</a> *&#160;</td>
 231           <td class="paramname"> <em>S</em>, </td>
 232         </tr>
 233         <tr>
 234           <td class="paramkey"></td>
 235           <td></td>
 236           <td class="paramtype"><a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a>&#160;</td>
 237           <td class="paramname"> <em>X</em>, </td>
 238         </tr>
 239         <tr>
 240           <td class="paramkey"></td>
 241           <td></td>
 242           <td class="paramtype"><a class="el" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0">q31_t</a>&#160;</td>
 243           <td class="paramname"> <em>Y</em>&#160;</td>
 244         </tr>
 245         <tr>
 246           <td></td>
 247           <td>)</td>
 248           <td></td><td><code> [static]</code></td>
 249         </tr>
 250       </table>
 251 </div>
 252 <div class="memdoc">
 253
 254 <p>Q7 bilinear interpolation. </p>
 255 <dl><dt><b>Parameters:</b></dt><dd>
 256   <table class="params">
 257     <tr><td class="paramdir">[in,out]</td><td class="paramname">*S</td><td>points to an instance of the interpolation structure. </td></tr>
 258     <tr><td class="paramdir">[in]</td><td class="paramname">X</td><td>interpolation coordinate in 12.20 format. </td></tr>
 259     <tr><td class="paramdir">[in]</td><td class="paramname">Y</td><td>interpolation coordinate in 12.20 format. </td></tr>
 260   </table>
 261   </dd>
 262 </dl>
 263 <dl class="return"><dt><b>Returns:</b></dt><dd>out interpolated value. </dd></dl>
 264
 265 <p>Definition at line <a class="el" href="arm__math_8h_source.html#l06962">6962</a> of file <a class="el" href="arm__math_8h_source.html">arm_math.h</a>.</p>
 266
 267 </div>
 268 </div>
 269 </div>
 270 <!--- window showing the filter options -->
 271 <div id="MSearchSelectWindow"
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