Manual Pages for UNIX Operating System command usage for man mlib_ImageNormCrossCorrel_Fp

mediaLib Library Functions    mlib_ImageNormCrossCorrel_Fp(3MLIB)



NAME
     mlib_ImageNormCrossCorrel_Fp - normalized cross correlation

SYNOPSIS
     cc [ flag... ] file... -lmlib [ library... ]
     #include 

     mlib_status mlib_ImageNormCrossCorrel_Fp(mlib_d64 *correl,
          const mlib_image *img1, const mlib_image *img2, const mlib_d64 *mean2,
          const mlib_d64 *sdev2);


DESCRIPTION
     The  mlib_ImageNormCrossCorrel_Fp()  function  computes  the
     normalized  cross-correlation coefficients between a pair of
     floating-point images, on a per-channel basis.


     It uses the following equations:

                      w-1 h-1
                      SUM SUM (d1[x][y][i] * d2[x][y][i])
                      x=0 y=0
         correl[i] = -------------------------------------
                                s1[i] * s2[i]

       d1[x][y][i] = img1[x][y][i] - m1[i]

       d2[x][y][i] = img2[x][y][i] - m2[i]

                       1     w-1 h-1
             m1[i] = ----- * SUM SUM img1[x][y][i]
                      w*h    x=0 y=0

                       1     w-1 h-1
             m2[i] = ----- * SUM SUM img2[x][y][i]
                      w*h    x=0 y=0

                           w-1 h-1
             s1[i] = sqrt{ SUM SUM (img1[x][y][i] - m1[i])**2 }
                           x=0 y=0

                           w-1 h-1
             s2[i] = sqrt{ SUM SUM (img2[x][y][i] - m2[i])**2 }
                           x=0 y=0



     where w and h are  the  width  and  height  of  the  images,
     respectively; m1 and m2 are the mean arrays of the first and
     second images, respectively; s1 and s2 are the un-normalized
     standard  deviation  arrays  of the first and second images,



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mediaLib Library Functions    mlib_ImageNormCrossCorrel_Fp(3MLIB)



     respectively.


     In usual cases, the normalized cross-correlation coefficient
     is in the range of [-1.0, 1.0].  In the case of (s1[i] == 0)
     or (s2[i] == 0), where a constant image channel is involved,
     the  normalized  cross-correlation coefficient is defined as
     follows:

           #define signof(x) ((x > 0) ? 1 : ((x < 0) ? -1 : 0))

           if ((s1[i] == 0.) || (s2[i] == 0.)) {
               if ((s1[i] == 0.) && (s2[i] == 0.)) {
                  if (signof(m1[i]) == signof(m2[i]) {
                      correl[i] = 1.0;
                  } else {
                      correl[i] = -1.0;
                  }
               } else {
                   correl[i] = -1.0;
               }
           }



     The two images must have the same type, the same  size,  and
     the  same  number  of  channels.  They can have 1, 2, 3 or 4
     channels. They can be of type MLIB_FLOAT or MLIB_DOUBLE.


     If (mean2 == NULL) or (sdev2 == NULL), then m2  and  s2  are
     calculated  in this function according to the formulas shown
     above.  Otherwise, they are calculated as follows:

           m2[i] = mean2[i];
           s2[i] = sdev2[i] * sqrt(w*h);



     where mean2 and sdev2 can be the output of  mlib_ImageMean()
     and mlib_ImageStdDev(), respectively.


     In some cases, the resulting coefficients of  this  function
     could be NaN, Inf, or -Inf.

PARAMETERS
     The function takes the following arguments:

     correl    Pointer to normalized cross correlation array on a
               channel basis. The array must be the size of chan-
               nels in the images. correl[i] contains the  cross-



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mediaLib Library Functions    mlib_ImageNormCrossCorrel_Fp(3MLIB)



               correlation of channel i.


     img1      Pointer to first image.


     img2      Pointer to second image.


     mean2     Pointer to the mean array of the second image.


     sdev2     Pointer to the standard  deviation  array  of  the
               second image.


RETURN VALUES
     The function returns MLIB_SUCCESS if  successful.  Otherwise
     it returns MLIB_FAILURE.

ATTRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:



     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Interface Stability         | Committed                   |
    |_____________________________|_____________________________|
    | MT-Level                    | MT-Safe                     |
    |_____________________________|_____________________________|


SEE ALSO
     mlib_ImageAutoCorrel(3MLIB), mlib_ImageAutoCorrel_Fp(3MLIB),
     mlib_ImageCrossCorrel(3MLIB),
     mlib_ImageCrossCorrel_Fp(3MLIB),
     mlib_ImageNormCrossCorrel(3MLIB), attributes(5)















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