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### 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.

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