5.3     Histogram
  This menu groups operations for finding and transforming
image histograms. nip2 represents histograms and lookup
tables as images with Type set to Histogram. Histograms may
have pixels in any format and any number of bands. You
can only find histograms of unsigned 8- and 16-bit
images.
    
- 
New 
- This makes a new ramp histogram. A set of sliders
    let you adjust the shape. Use Map Histogram to apply
    your ramp to an image.
    Build  LUT  from  Scatter  makes  a  histogram  from  a
    matrix of (x,y) values.
     Tag Image as Histogram marks an image as actually
    being a histogram after all.
     Tone Curve builds a tone curve which you can later
    apply to an image.
     
- 
Find 
- A  one  dimensional  histogram  treats  each  band
    as  an  independent  variable.  An  n-dimensional
    histogram   treats   each   pixel   as   a   vector   of   n
    elements, where n is the number of bands in the
    image.
    
- 
Map 
- Looks up each pixel in the input in the histogram
    and sends the found value to the output.
    
- 
Equalise 
- Find the global or locally histogram equalised
    image.
    
- 
Cumulative 
- Use
    this and friends to calculate a cumulative histogram
    (integrate), normalise a histogram and match two
    histograms.                                         
- 
  Find Profile  
- Searches from the edges of an image for the
          first non-zero pixel and returns a profile histogram.
          
- 
  Find Projections  
- Sum columns and rows in an image.
          
- 
  Plot Slice  
- Mark  a  guide  on  an  image  (drag  from  the
          image rulers, or click File / New / Guide) and click
          Plot Slice to make a histogram which is a horizontal
          or vertical slice through an image. Use Extract Arrow
           to extract the area around an arrow or guide. Use
          Plot Object to make a plot of any object.