Need Some Clue for Implement Adapter of Cornerstone Rectangle Annotation

[jenhaoyang]

I saw these implement hints from dcmjs/src/utilities/TID300/index.js. But I am not clear about those hint, could you explain more detail?
Is that are the Hierarchy I need to implement in dcmjs/src/utilities/TID300/Rectangle.js like dcmjs/src/utilities/TID300/Ellipse.js do?
I saw "Graphic Type: POLYLINE" and I wondering Rectangle.js should change Graphic Type to POLYLINE. But what is the meaning of following line?
TID 1500 MeasurementReport
--TID 1501 Measurement Group
---Measurement Group (DCM 125007)
----TID 300 Measurement

dcmjs/src/utilities/TID300/index.js

Lines 25 to 35 in 0e1e292

	// - Cornerstone Rectangle ROI
	//
	// Hierarchy
	// TID 1500 MeasurementReport
	// --TID 1501 Measurement Group
	// ---Measurement Group (DCM 125007)
	// ----TID 300 Measurement
	// ------SCOORD. Graphic Type: POLYLINE
	// ------ Use concept corresponding to Rectangle measurement
	//
	// http://dicom.nema.org/medical/dicom/current/output/html/part16.html#sect_TID_4019

The hint also mention about "This should be the same as a Freehand ROI, more or less." Is that mean I need to use src/adapters/Cornerstone/Freehand.js as my template for implement src/adapters/Cornerstone/Rectangle.js rather than src/adapters/Cornerstone/EllipticalRoi.js?

dcmjs/src/utilities/TID300/index.js

Lines 37 to 42 in 0e1e292

	// OR
	// Note: This should be the same as a Freehand ROI, more or less. We add a TID 4019: Algorithm Identification flag to specify that this was created (and should be rehydrated) into a Rectangle ROI.
	// TODO: Should we use a Derivation instead? http://dicom.nema.org/medical/dicom/current/output/html/part16.html#DCM_121401
	// Should specify the Area measured in mmˆ2, including the units in UCUM
	// Should specify the Mean Modality Pixel Value measured in whatever units the image is in
	// Should specify the Standard Deviation Modality Pixel Value measured in whatever units the image is in

Originally posted by @jenhaoyang in #137 (comment)