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NAME

       im_cntlines, im_profile - calculate transitions between black and white
       pels horizontally or vertically

SYNOPSIS

       #include <vips/vips.h>

       int im_profile(in, out, dir)
       IMAGE *in, *out;
       int dir;

       int im_cntlines(in, nolines, dir)
       IMAGE *in;
       double *nolines;
       int dir;

DESCRIPTION

       im_profile(3) searches inward from the edge of the image and finds  the
       first  non-zero  pixel.   It  outputs an image containing a list of the
       offsets for each row or column.

       If dir ==0, then im_profile(3) searches down from the top edge, writing
       an  image as wide as the input image, but only 1 pixel high, containing
       the number of pixels down to the first non-zero pixel for  each  column
       of input pixels.

       If  dir  ==1,  then  im_profile(3)  searches across from the left edge,
       writing an image as high as the input image, but  only  1  pixel  wide,
       containing  the number of pixels across to the first non-zero pixel for
       each row of input pixels.

       im_cntlines(3) calculates the number of transitions between  black  and
       white  pixels of an image.  If dir is 1 then all transitions across the
       vertical direction are calculated for all Xsize lines of the image.  If
       dir  is  0  then all transitions along the horizontal direction for all
       Ysize lines  are  calculated.   The  function  returns  the  number  of
       transitions  divided  by twice the number of the corresponding Xsize of
       Ysize lines.  The program is primarily used to calculate the number  of
       unbroken horizontal (dir=0) or vertical lines (dir=1) that exist within
       an image.  Input image in can have only one channel.

RETURN VALUE

       All functions returns 0 on success and -1 on error.

SEE ALSO

       im_erode(3), im_dilate(3).

                                  14 May 1991                         LINES(3)