min_max_graymin_max_grayMinMaxGrayMinMaxGraymin_max_gray (Operator)

Name

min_max_graymin_max_grayMinMaxGrayMinMaxGraymin_max_gray — Determine the minimum and maximum gray values within regions.

Signature

min_max_gray(Regions, Image : : Percent : Min, Max, Range)

Description

The operator min_max_graymin_max_grayMinMaxGrayMinMaxGraymin_max_gray creates the histogram of the absolute frequencies of the gray values within RegionsRegionsRegionsregionsregions in the input image ImageImageImageimageimage (see gray_histogray_histoGrayHistoGrayHistogray_histo) and calculates the number of pixels PercentPercentPercentpercentpercent corresponding to the area of the input image. Then it goes inwards on both sides of the histogram by this number of pixels and determines the smallest and the largest gray value:

Example:

With area = 60, PercentPercentPercentpercentpercent = 5, d.h. i.e. 3 pixels, histogram = [2,8,0,7,13,0,0,...,0,10,10,5,3,1,1],

Minimum = 0, Maximum = 255, range = 255

min_max_graymin_max_grayMinMaxGrayMinMaxGraymin_max_gray returns: MinMinMinminmin = 1, MaxMaxMaxmaxmax = 253, RangeRangeRangerangerange = 252.

For images of type int4, int8, and real, the above calculation is not performed via histograms, but using a rank selection algorithm. If PercentPercentPercentpercentpercent is set to 50, MinMinMinminmin = MaxMaxMaxmaxmax = Median. If PercentPercentPercentpercentpercent is 0 no histogram is calculated in order to enhance the runtime.

Attention

Note that the operator min_max_graymin_max_grayMinMaxGrayMinMaxGraymin_max_gray only considers the given RegionsRegionsRegionsregionsregions and ignores any previously set domain of the input image ImageImageImageimageimage.

Execution Information

Multithreading type: reentrant (runs in parallel with non-exclusive operators).
Multithreading scope: global (may be called from any thread).
Automatically parallelized on tuple level.

Parameters

RegionsRegionsRegionsregionsregions (input_object) region(-array) → object

Regions, the features of which are to be calculated.

ImageImageImageimageimage (input_object) singlechannelimage → object (byte / direction / cyclic / int1 / int2 / uint2 / int4 / int8 / real)

Gray value image.

PercentPercentPercentpercentpercent (input_control) number → (real / integer)

Percentage below (above) the absolute maximum (minimum).

Default: 0

Suggested values: 0, 1, 2, 5, 7, 10, 15, 20, 30, 40, 50

Restriction: 0 <= Percent && Percent <= 50

MinMinMinminmin (output_control) real(-array) → (real)

“Minimum” gray value.

MaxMaxMaxmaxmax (output_control) real(-array) → (real)

“Maximum” gray value.

Assertion: Max >= Min

RangeRangeRangerangerange (output_control) real(-array) → (real)

Difference between Max and Min.

Assertion: Range >= 0

Example (HDevelop)

* Threshold segmentation with training region:
read_image(Image,'fabrik')
draw_region(Region,WindowHandle)
min_max_gray(Region,Image,5,Min,Max,Range)
threshold(Image,SegmentedRegion,Min,Max)
dev_display(SegmentedRegion)

Example (C)

/* Threshold segmentation with training region: */
read_image(&Image,"fabrik");
draw_region(&Region,WindowHandle);
min_max_gray(Region,Image,5.0,&Min,&Max,NULL);
threshold(Image,&SegmentedRegion,Min,Max);
disp_region(SegmentedRegion,WindowHandle);

Example (C++)

#include "HalconCpp.h"
using namespace Halcon;
#include "HIOStream.h"
#if !defined(USE_IOSTREAM_H)
using namespace std;
#endif

main()
{
  HImage   img ("fabrik");
  HWindow  w;

  Htuple   range, max;

  img.Display (w);
  w.Click ();

  HRegion   reg = w.DrawRegion ();
  HImage    rdd = img.ReduceDomain (reg);

  Htuple min = reg.MinMaxGray (rdd, 5, &max, &range);

  HRegionArray imgseg = ((img >= min[0].I()).Connection() &
                         (img <= max[0].I()).Connection());

  cout << "Min = " << min[0].I() << endl;
  cout << "Max = " << max[0].I() << endl;

  imgseg.Display (w);
  w.Click ();
  return(0);
}

Example (HDevelop)

* Threshold segmentation with training region:
read_image(Image,'fabrik')
draw_region(Region,WindowHandle)
min_max_gray(Region,Image,5,Min,Max,Range)
threshold(Image,SegmentedRegion,Min,Max)
dev_display(SegmentedRegion)