intensity__ ( Regions, Image : : : Mean, Deviation )

Calculate the mean and deviation of gray values.

The operator intensity__ calculates the mean and the deviation of the gray values in the input image within Regions. If R is a region, p a pixel from R with the gray value g(p) and F the plane (F = |R|), the features are defined by:

                ----      
                \
   Mean      =  /     g(p)
                ----      
               p in R
               -----------
                    F

                 -----------------------
                 |    ----      
                 | 1  \                2
   Deviation =   | -  /     (g(p)-Mean)
               \ | F  ----      
                \|   p in R


Attention

The calculation of Deviation does not follow the usual definition if the region of the image contains only one pixel. In this case 0.0 is returned.


Parameters

Regions (input_object)
region(-array) -> object
Regions the features of which are to be calculated.

Image (input_object)
image -> object : byte / int1 / int2 / int4 / real
Gray value image.

Mean (output_control)
real(-array) -> real
Mean gray value of a region.

Deviation (output_control)
real(-array) -> real
Deviation of gray values within a region.


Complexity

If F is the area of the region, the runtime complexity is O(F).


Result

The operator intensity__ returns the value TRUE. The behavior in case of empty input (no input images available) is set via the operator set_system(::'no_object_result',<Result>:), the behavior in case of empty region is set via set_system(::'empty_region_result',<Result>:). If necessary an exception is raised.


Possible Successors

threshold__


Alternatives

select_grey__, min_max__


See also

mean__, deviation__, histo__



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