gray_histo_range — Calculate the gray value distribution of a single channel image within a certain gray value range.
gray_histo_range calculates the gray value distribution Histo of the single channel Image within Regions and the gray value range [Min,Max]. The values for Min and Max are rounded down to the next integer if the Image is not of type 'real'. The gray value range is divided into NumBins bins of the same size, which is returned in BinSize. If a gray value lies between two bins the gray value is assigned to the smaller bin. If the Image is of type 'real' BinSize = (Max - Min) / NumBins. If the Image has discrete gray values the size of a bin is computed with BinSize = (Max - Min + 1) / NumBins. Since the accuracy of the histogram Histo can be adjusted with NumBins, the calculation of the gray value histogram with gray_histo_range is most useful for images of type 'real' and images of type 'integer', which have a high bit depth.
Note that the operator gray_histo_range only considers the given Regions and ignores any previously set domain of the input image Image.
If the Image has discrete gray values the value of BinSize may cause the following effects: For BinSize > 1 multiple neighboring gray values are assigned to the same bin. If BinSize is no integer the gray values are distributed uneven among the bins, e.g., for BinSize = 1.5 the first and second gray value are assigned to the first bin, the third gray value is assigned to the second bin, and the fourth and fifth gray value are assigned to the third bin. This becomes noticeable in several peeks in the histogram Histo. If BinSize < 1 some classes are not assigned by any gray value, e.g., for BinSize = 0.5 the first gray value is assigned to the first bin and the second gray value is assigned to the third bin. The histogram Histo shows some gaps, which resembles the structure of a comb.
If the Image is of type 'real' and Min = Max, all pixels of the corresponding gray value are assigned only to the first bin.
Region in which the histogram is to be calculated.
Minimum gray value.
Default value: 0
Suggested values: 0
Maximum gray value.
Default value: 255
Suggested values: 255
Restriction: Max >= Min
Number of bins.
Default value: 256
Suggested values: 16, 32, 64, 128, 256
Restriction: NumBins >= 1
Histogram to be calculated.
If the parameters are valid, the operator gray_histo_range returns the value 2 (H_MSG_TRUE). If necessary an exception is raised.