gray_histo — Calculate the gray value distribution.
gray_histo calculates for the image
Regions the absolute
AbsoluteHisto) and relative (
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'-, 'int2'-, 'uint2'-, 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
Note that the operator
gray_histo only considers
Regions and ignores any previously set domain
of the input image
Real, int2, uint2, and int4 images are reduced to 256 gray values.
gray_histo can be executed on OpenCL devices for byte, int1,
directional and cyclic images if the OpenCL device supports the
cl_khr_local_int32_base_atomics and cl_khr_global_int32_base_atomics
extensions (which are optional in OpenCL 1.0). Unlike most other HALCON
gray_histo can be substantially slower on an OpenCL
device if the
Image is not completely included in the
OpenCL support is not available in HALCON XL, as 64 bit atomic integer arithmetic would be required.
Region in which the histogram is to be calculated.
→object (byte* / cyclic* / direction* / int1* / int2 / uint2 / int4 / real) *allowed for compute devices
Image the gray value distribution of which is to be calculated.
Absolute frequencies of the gray values.
Frequencies, normalized to the area of the region.
If F is the area of the region the runtime complexity is O(F + 255).
gray_histo 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
If necessary an exception is raised.