Host nodes: DepthMerger.

[kkeroo]

This PR adds first host node called DepthMerger. The node merges normal ImgDetections or ImgDetectionsExtended with depth information into SpatialImgDetections. The node is taken from experiments host-nodes folder and slightly adjusted so it works with ImgDetectionsExtended. We also introduce parameter shrinking_factor that is responsible for optionally shrinking the ROI for calculating depth values. This is useful because sometimes bounding-box also includes background and so the mean depth value is affected. E.g. In bouding-box of a human the shrinking factor will shrink the ROI into the human torso.

I am not sure about the folder hierarchy. I was thinking of placing it in the helpers folder under specific subfolders. Maybe there is something better?

The proposed node works with rewritten experiments: Human-Machine safety and social distancing.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 99.10714% with 1 line in your changes missing coverage. Please review.

Project coverage is 37.78%. Comparing base (d9770af) to head (adc4f65).
Report is 1 commits behind head on main.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
depthai_nodes/nodes/depth_merger.py	98.30%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #163      +/-   ##
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+ Coverage   36.05%   37.78%   +1.72%     
==========================================
  Files          72       75       +3     
  Lines        4024     4137     +113     
==========================================
+ Hits         1451     1563     +112     
- Misses       2573     2574       +1     

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[dominik737]

Looks good. I would have a nodes folder along (same level as) the ml folder. Since many of the nodes are actually not related to ml. Then if there are too many nodes, we can group then in the nodes folder into subfolders.

[dominik737]

@klemen1999 Also I just remembered we were talking about tests. Should they be implemented now in those PRs that add nodes?

[klemen1999]

Generally LGTM

Agree on moving nodes into separate folder (same level as ml) and not nesting them into subfolders at least for now, we can do that later on if needed.

@klemen1999 Also I just remembered we were talking about tests. Should they be implemented now in those PRs that add nodes?

Good catch, we should make tests for every new node as potentially many different experiments will rely on their specifics. We can sync offline what/how to test.

[kkeroo]

Okay, I moved the added DepthMerger node to the depthai_nodes/nodes folder and exposed it in the __init__.py. We can import it as from depthai_nodes.nodes import DepthMerger.

[jkbmrz]

LGTM. Just adding a small stylistic suggestion.

Also, I agree on having the nodes folder at the same level as ml. I'm wondering, though, if we should also move there the contents of thedepthai_nodes/ml/helpers folder?

[kkeroo]

I added the tests for DepthMerger and HostSpatialsCalc in adc4f65.

[klemen1999]

LGTM, thanks!