A contour length follows a selected digital path. Counting its listed vertices is a different operation.
Define the measured path
A contour arc length sums distances along its represented curve, with a choice of whether the path is closed. The listed vertices and their coordinate units determine this digital geometry. Vertex count alone does not describe those distances or specify the length of the closing segment. Primary reference: OpenCV contour arc length and closed-curve convention.
For an original record, preserve the ordered point sequence and closed-path flag. Retain any contour simplification separately. A path measured in pixel coordinates needs an additional geometric basis before it becomes a physical perimeter, and that conversion should not be inferred from the display size.
Trace a fictional triangle
Take points (0,0), (3,0) and (3,4), in invented coordinate units. The open path has segment lengths 3 and 4, totaling 7. Closing it adds a segment of length 5 back to the first point, giving a total of 12. There are still only three listed vertices.
The difference comes from the closing convention, not from another sampled object. If the coordinate unit is a pixel interval, these are interval lengths rather than automatically millimeters. The fictional triangle supplies no calibration or verified physical boundary of a pack.
Retain the representation history
Prepare an original diagram labeling each segment and the closing edge. If a digital contour is resampled or simplified, compare the retained path before comparing its length. Two point counts can match while their spacing differs; two path lengths can match while the shapes differ.
This guide recommends no acceptance perimeter and claims no HM measurement accuracy. Its reader decision is whether a reported number describes an explicitly represented curve, including its closure, rather than a vertex count or an unsupported physical dimension.
Customer Questions
What is the fictional open-path length?
Seven coordinate units.
What does closing the triangle add?
A five-unit segment, making twelve.
Do three vertices imply length three?
No. Their segment distances determine the path length.
Primary References
These references support the technical principles discussed in this guide. The worked examples and review questions are educational.
Discuss Your Machine Requirement
Share your product, container, required output and the evidence needed for your technical review.
Request a Technical Review