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+<?php
+/*=======================================================================
+// File:        JPGRAPH_MESHINTERPOLATE.INC.PHP
+// Description: Utility class to do mesh linear interpolation of a matrix
+// Created:     2009-03-09
+// Ver:         $Id: jpgraph_meshinterpolate.inc.php 1709 2009-07-30 08:00:08Z ljp $
+//
+// Copyright (c) Asial Corporation. All rights reserved.
+//========================================================================
+*/
+  
+/**
+* Utility function to do linear mesh interpolation
+* @param $aDat Matrix to interpolate
+* @param $aFactor Interpolation factor  
+*/
+function doMeshInterpolate( &$aData, $aFactor ) {
+    $m = new MeshInterpolate();
+    $aData = $m->Linear($aData,$aFactor);
+}
+
+/**
+ * Utility class to interpolate a given data matrix
+ *
+ */
+class MeshInterpolate {
+    private $data = array();
+
+   /**
+    * Calculate the mid points of the given rectangle which has its top left
+    * corner at $row,$col. The $aFactordecides how many spliots should be done.
+    * i.e. how many more divisions should be done recursively
+    *
+    * @param $row Top left corner of square to work with
+    * @param $col Top left corner of square to work with
+    * $param $aFactor In how many subsquare should we split this square. A value of 1 indicates that no action
+    */
+    function IntSquare( $aRow, $aCol, $aFactor ) {
+        if ( $aFactor <= 1 )
+            return;
+
+        $step = pow( 2, $aFactor-1 );
+
+        $v0 = $this->data[$aRow][$aCol];
+        $v1 = $this->data[$aRow][$aCol + $step];
+        $v2 = $this->data[$aRow + $step][$aCol];
+        $v3 = $this->data[$aRow + $step][$aCol + $step];
+
+        $this->data[$aRow][$aCol + $step / 2] = ( $v0 + $v1 ) / 2;
+        $this->data[$aRow + $step / 2][$aCol] = ( $v0 + $v2 ) / 2;
+        $this->data[$aRow + $step][$aCol + $step / 2] = ( $v2 + $v3 ) / 2;
+        $this->data[$aRow + $step / 2][$aCol + $step] = ( $v1 + $v3 ) / 2;
+        $this->data[$aRow + $step / 2][$aCol + $step / 2] = ( $v0 + $v1 + $v2 + $v3 ) / 4;
+
+        $this->IntSquare( $aRow, $aCol, $aFactor-1 );
+        $this->IntSquare( $aRow, $aCol + $step / 2, $aFactor-1 );
+        $this->IntSquare( $aRow + $step / 2, $aCol, $aFactor-1 );
+        $this->IntSquare( $aRow + $step / 2, $aCol + $step / 2, $aFactor-1 );
+    }
+
+    /**
+     * Interpolate values in a matrice so that the total number of data points
+     * in vert and horizontal axis are $aIntNbr more. For example $aIntNbr=2 will
+     * make the data matrice have tiwce as many vertical and horizontal dta points.
+     *
+     * Note: This will blow up the matrcide in memory size in the order of $aInNbr^2
+     *
+     * @param  $ &$aData The original data matricde
+     * @param  $aInNbr Interpolation factor
+     * @return the interpolated matrice
+     */
+    function Linear( &$aData, $aIntFactor ) {
+        $step = pow( 2, $aIntFactor-1 );
+
+        $orig_cols = count( $aData[0] );
+        $orig_rows = count( $aData );
+        // Number of new columns/rows
+        // N = (a-1) * 2^(f-1) + 1
+        $p = pow( 2, $aIntFactor-1 );
+        $new_cols = $p * ( $orig_cols - 1 ) + 1;
+        $new_rows = $p * ( $orig_rows - 1 ) + 1;
+
+        $this->data = array_fill( 0, $new_rows, array_fill( 0, $new_cols, 0 ) );
+        // Initialize the new matrix with the values that we know
+        for ( $i = 0; $i < $new_rows; $i++ ) {
+            for ( $j = 0; $j < $new_cols; $j++ ) {
+                $v = 0 ;
+                if ( ( $i % $step == 0 ) && ( $j % $step == 0 ) ) {
+                    $v = $aData[$i / $step][$j / $step];
+                }
+                $this->data[$i][$j] = $v;
+            }
+        }
+
+        for ( $i = 0; $i < $new_rows-1; $i += $step ) {
+            for ( $j = 0; $j < $new_cols-1; $j += $step ) {
+                $this->IntSquare( $i, $j, $aIntFactor );
+            }
+        }
+
+        return $this->data;
+    }
+}
+  
+?>