A numerical threshold belongs to the intensity representation. Copying an integer cutoff unchanged into a normalized array changes the comparison.
Retain the intensity scale
An intensity-image conversion can rescale unsigned integer values into a normalized floating range. That is different from a type cast that only changes storage while keeping numerical values. A threshold therefore needs its input scale, type and conversion route attached before comparisons are reused. Primary reference: MathWorks integer intensity rescaling.
For an original worksheet, specify whether values represent unsigned eight-bit intensities or normalized values. Keep indexed images out of this assumed intensity conversion; their value meanings differ. A floating type alone does not prove that the array's numbers have been normalized.
Translate a fictional cutoff
For a defined unsigned eight-bit intensity scale 0 through 255, let normalized value be integer value divided by 255. An integer cutoff of 128 becomes 128/255, approximately 0.50196. A pixel at 200 becomes approximately 0.78431 and remains above the correspondingly converted cutoff.
Comparing that normalized pixel with the unchanged cutoff 128 would instead reject it. The invented conversion preserves the stated ordering when both value and cutoff use one scale. It does not establish an inspection threshold, a linear-light interpretation or a particular application's stored data type.
Check values and cutoff together
Prepare an original paired-value record listing before-conversion values, converted values and both cutoff definitions. Verify the actual conversion with a known non-endpoint sample. Do not rely only on a full-black or full-white display to prove that an intermediate numerical cutoff has the correct meaning.
This guide gives no HM segmentation setting or acceptance level. Its reader decision is whether a threshold and its input array share the same intensity scale. Keep storage-range conversion separate from color transfer-function decoding and from evidence that the selected threshold serves the actual feature question.
Customer Questions
What is the fictional normalized cutoff?
128 divided by 255, approximately 0.50196.
Is the converted value 200/255 above it?
Yes.
Does floating storage alone prove normalization?
No. The conversion route must be known.
Primary References
These references support the technical principles discussed in this guide. The worked examples and review questions are educational.
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