histo__ ( Regions, Image : : : AbsoluteHisto, RelativeHisto )

Calculate the gray value distribution.

The operator histo__ calculates for the image (Image) within Regions the absolute (AbsoluteHisto) and relative (RelativeHisto) histogram of the gray values.

Both histograms are tupels of 256 values, which --- beginning at 0 --- contain the frequencies of the individual gray values of the image.

AbsoluteHisto indicates the absolute frequencies of the gray values in integers, and RelativeHisto indicates the relative, i.e. the absolute frequencies divided by the area of the image as floating point numbers.

real- and int4-images are transformed into byte-images (first the largest and smallest gray value in the image are determined, and then the original gray values are mapped linearly into the area 0..255) and then processed as mentioned above. The histogram can also be returned directly as a graphic via the operators set_paint(::'histogram':) and disp_image.


Attention

Real and int4 images are reduced to 256 gray values.


Parameters

Regions (input_object)
region(-array) -> object
Region in which the histogram is to be calculated.

Image (input_object)
image -> object : byte / cyclic / direction / int4 / real
Image the gray value distribution of which is to be calculated.

AbsoluteHisto (output_control)
histogram.values-array -> integer
Absolute frequencies of the gray values.

RelativeHisto (output_control)
histogram.values-array -> real
Frequencies, normalized to the area of the region.


Complexity

If F is the area of the region the runtime complexity is O(F + 255).


Result

The operator histo__ returns the value TRUE if the image has defined gray values and the parameters are correct. 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

histo_to_thresh, histo_to_region


Alternatives

min_max__, intensity__


See also

set_paint, disp_image, histo_2dim__, scale_max, entropy2__



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