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5.5 Histogram
This menu groups operations for finding and transforming image histograms.
nip represents histograms and lookup tables as images with SPMquot
type"
set to SPMquot
histogram". Histograms may have pixels in any format and any
number of bands.
See also Find_profile in the Morphology menu.
- Hist_find
- Use this to find the histogram for an image. Histograms of 8-bit
images are displayed as 256
256 images. Histograms of
16-bit images are displayed as
by
pixel images, where
is
the maximum pixel value and
is the maximum frequency.
- Hist_find_nD
- Use this to find an
-dimensional histogram of an
-band image,
where
is 1, 2 or 3. The bins=> member sets the number of bins
each axis is divided into. Works for 8- and 16-bit images.
- Hist_map
- Use this to map an image through a histogram. Select the
histogram first and then the image and click Hist_map=>. The
histogram must have either 1 band (in which case all image bands
are passed though the same histogram band), or the same number of
bands as the image.
- Hist_cumulative
- Use this to calculate a cumulative histogram. It works for
any unsigned integer format.
- Hist_normalise
- Use this to normalise a histogram. The maximum histogram value
becomes equal to the number of pixels in the histogram. In effect,
the histogram becomes `square'. Each channel is normalised separately.
- Hist_match
- Use this to match the PDFs of two histograms. They need to have the
same number of bands.
- Hist_equalise
- Use Global on an image to do global histogram equalisation. Mark
a region on an image and use Local to equalise with a roving
window the size of the region.
- Guide_slice
- Mark a guide on an image (drag from the rulers in an image display
window) and use this to graph the pixels along the slice.
Next: 5.6 Image
Up: 5. Image processing menus
Previous: 5.4 Format
  Contents
John Cupitt
2003-07-21