gray_histo_abs🔗
Short description🔗
gray_histo_abs — Calculate the gray value distribution.
Signature🔗
gray_histo_abs( region Region, image Image, number Quantization, out histogram AbsoluteHisto )
Description🔗
The operator gray_histo_abs calculates for the image
(Image) within Region the absolute
(AbsoluteHisto) ) histogram of the gray values.
The parameter Quantization defines, how many frequencies of
neighbored gray values are added for one frequency value. The resulting
histogram AbsoluteHisto is a tuple, whose indices are mapped on the
gray values of the input image Image and whose elements contain the
frequencies of the gray values. The indices \(i\) of the frequency value
are calculated from the gray values \(g\) and the quantization \(q\) as follows:
-
For unsigned image types:
\[\begin{eqnarray*} i = \left\lceil {\frac{g+0.5}{q}}\right\rceil \end{eqnarray*}\] -
For signed image types:
\[\begin{eqnarray*} i = \left\lceil {\frac{g-(MIN-0.5)}{q}}\right\rceil \end{eqnarray*}\]
whereas MIN denotes the minimal gray value, e.g., -128 for an int1 image type. Therefore, the size of the tuple results from the ratio of the full domain of gray values and the quantization, e.g., for images of int2 in \(\lceil \frac{65536}{3.0} \rceil = 21846\). The origin gray value of the signed image types int1 resp. int2 is mapped on the index 128 resp. 32768, negative resp. positive gray values have smaller resp. greater indices.
Attention🔗
Note that the operator gray_histo_abs only considers
the given Region and ignores any previously set domain
of the input image Image.
Execution information🔗
Execution information
-
Multithreading type: reentrant (runs in parallel with non-exclusive operators).
-
Multithreading scope: global (may be called from any thread).
-
Automatically parallelized on internal data level.
Parameters🔗
Region (input_object) region → object
Region in which the histogram is to be calculated.
Image (input_object) singlechannelimage → object (byte / cyclic / direction / int1 / int2 / uint2)
Image the gray value distribution of which is to be calculated.
Quantization (input_control) number → (real / integer)
Quantization of the gray values.
Default: 1.0
Suggested values: 1.0, 2.0, 3.0, 5.0, 10.0
Restriction: Quantization >= 1.0
AbsoluteHisto (output_control) histogram-array → (integer)
Absolute frequencies of the gray values.
Result🔗
The operator gray_histo_abs returns the value 2 (H_MSG_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.
Combinations with other operators🔗
Combinations
Possible successors
histo_to_thresh, gen_region_histo
Alternatives
min_max_gray, intensity, gray_histo, gray_histo_range
See also
Module🔗
Foundation