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lib: Add API docs for fpi_img comparison functions

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Vasily Khoruzhick 2018-12-03 14:08:24 +01:00 committed by Bastien Nocera
parent dd24cf57c6
commit c9733d27df
1 changed files with 33 additions and 2 deletions
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35
libfprint/fpi-img.c
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@ -615,7 +615,22 @@ API_EXPORTED int fp_minutia_get_coords(struct fp_minutia *minutia, int *coord_x,
return 0;
}
/* Calculate squared standand deviation */
/**
* fpi_std_sq_dev:
* @buf: buffer (usually bitmap, one byte per pixel)
* @size: size of @buffer
*
* Calculates the squared standard deviation of the individual
* pixels in the buffer, as per the following formula:
* |[<!-- -->
* mean = sum (buf[0..size]) / size
* sq_dev = sum ((buf[0.size] - mean) ^ 2)
* ]|
* This function is usually used to determine whether image
* is empty.
*
* Returns: the squared standard deviation for @buffer
*/
int fpi_std_sq_dev(const unsigned char *buf, int size)
{
int res = 0, mean = 0, i;
@ -638,7 +653,23 @@ int fpi_std_sq_dev(const unsigned char *buf, int size)
return res / size;
}
/* Calculate normalized mean square difference of two lines */
/**
* fpi_mean_sq_diff_norm:
* @buf1: buffer (usually bitmap, one byte per pixel)
* @buf2: buffer (usually bitmap, one byte per pixel)
* @size: buffer size of smallest buffer
*
* This function calculates the normalized mean square difference of
* two buffers, usually two lines, as per the following formula:
* |[<!-- -->
* sq_diff = sum ((buf1[0..size] - buf2[0..size]) ^ 2) / size
* ]|
*
* This functions is usually used to get numerical difference
* between two images.
*
* Returns: the normalized mean squared difference between @buf1 and @buf2
*/
int fpi_mean_sq_diff_norm(unsigned char *buf1, unsigned char *buf2, int size)
{
int res = 0, i;