gray_histo — Calculate the gray value distribution.
The operator gray_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'-, '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 set_paint(::WindowHandle,'histogram':) and disp_image.
Note that the operator gray_histo only considers the given Regions and ignores any previously set domain of the input image 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 operators, gray_histo can be substantially slower on an OpenCL device if the Image is not completely included in the Regions.
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.
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).
The operator 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 set_system(::'empty_region_result',<Result>:). If necessary an exception is raised.
min_max_gray, intensity, gray_histo_abs, gray_histo_range
set_paint, disp_image, histo_2dim, scale_image_max, entropy_gray