ROI visualization is off-by-one

[stuarteberg]

I think when NeuTu shows an ROI, it gets the border right on the upper/left side, but not on the lower/right side. Here's a screenshot that demonstrates the problem. In this screenshot, segmentation outside the ROI has been erased.

Of course, it's possible that my code which performed the ROI-based segmentation masking is off-by-one, and NeuTu is correct. But I think my test coverage is fairly good here. In any case, I need to figure out if the problem is on my end or NeuTu's.

FWIW, here's the dvid documentation for the roi endpoint:

Click for dvid docs

GET  <api URL>/node/<UUID>/<data name>/roi
POST <api URL>/node/<UUID>/<data name>/roi
DEL  <api URL>/node/<UUID>/<data name>/roi 

    Performs operations on an ROI depending on the HTTP verb.

    Example: 

    GET <api URL>/node/3f8c/medulla/roi

    Returns the data associated with the "medulla" ROI at version 3f8c.
    If an ROI is currently being created asynchronously, e.g., during an imageblk
    foreground command, then a HTTP status code 206 (Partial Content) is returned
    until the ROI is completely stored (HTTP status code 200).

    The "Content-type" of the HTTP response (and usually the request) are
    "application/json" for arbitrary binary data.  Returns a list of 4-tuples:

  	"[[0, 0, 0, 1], [0, 2, 3, 5], [0, 2, 8, 9], [1, 2, 3, 4]]"

	Each element is expressed as [z, y, x0, x1], which represents blocks with the block coordinates
	(x0, y, z) to (x1, y, z).  Each block is a chunking of voxel space using the BlockSize for 
	the ROI.

    Arguments:

    UUID          Hexadecimal string with enough characters to uniquely identify a version node.
    data name     Name of ROI data to save/modify or get.