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       im_histplot - graph an image of one horizontal or vertical line


       #include <vips/vips.h>

       int im_histplot(in, out)
       IMAGE *in, *out;


       im_histplot(3)  plots  a  graph  of a horizontal or vertical image file
       with one line. It is suitable for displaying the  output  of  histogram
       functions such as im_histgr(3) and for displaying line profiles.

       Note  that  if  you try to directly plot the result of im_histgr(3) you
       will often get a very, very large image, since im_histplot(3) will draw
       an  image  as high (or as wide) as the largest pixel value in the image
       (potentially huge).  Use  im_histnorm(3)  to  normalise  the  histogram
       maximum before plotting.

       The  input  image should be either one horizontal line (Ysize=1) or one
       vertical line (Xsize=1).  If the image is FMTUCHAR, the graph is  drawn
       as  256  by  line-length  pixels. For all other unsigned integer types,
       im_histplot(3) finds the image maximum, and draws the graph as  max  by
       line-length pixels.

       For  signed  integer  types,  im_histplot(3) finds minimum and maximum,
       moves min up to zero, and draws the graph as min +  max  by  line-lenth

       For  float  types, im_histplot(3) finds minimum and maximum, and scales
       the image range so as to make  the graph square.


       The function returns 0 on success and -1 on error.


       im_histgr(3), im_histnorm(3), im_extract(3).


       National Gallery and Birkbeck College, 1995

                                  10 May 1991