What an AOI is
An Area of Interest (AOI) is a polygon you draw — or that ZeroCount auto-detects for you — that tells the detection pipeline "only look for symbols inside this region". AOIs do two jobs:
- Speed. The detection pipeline is much faster when it doesn't have to scan the whole drawing.
- Accuracy. Excluding the legend, title block, and margin notes prevents false matches.
Every drawing in Stage 1 needs at least one AOI before detection will run. ZeroCount usually places one for you automatically.
AOI vs Zone — what's the difference?
This trips a lot of people up:
- AOIs filter detection before it runs. They control where symbols are searched for.
- Zones group markers after they've been placed. They control how counts are split in the Excel export.
Where AOIs live
Open the sidebar's marker list toolbar and click Zones & AOIs . The dropdown has two sections — find the AOIs section at the top.
Each AOI is listed as AOI 1, AOI 2, and so on, in the order they were created.
Showing or hiding AOIs
The Display AOIs toggle inside the AOIs section turns the polygon overlays on or off on the canvas. Hiding them temporarily is useful when they're obscuring something you want to see — they're still active even when hidden, just not drawn.
Locking AOIs
AOIs lock with a single click on the lock toggle:
- Unlocked — you can drag the corners and delete the AOI.
- Locked — drag and delete are blocked.
Lock once Stage 1 is set up to prevent accidental moves while you work in Stage 2. The delete button shows a tooltip — "Unlock AOIs before deleting" — when locked.
Recolouring an AOI
- 1
In the AOI list, click the colour swatch next to the AOI you want to recolour.
- 2
Pick from the 6-column colour grid.
- 3
Optionally adjust the Opacity slider — between 5 and 100%.
- 4
Click Apply.
AOI colour is purely visual — the detection pipeline doesn't care. Pick a colour that contrasts well with the drawing's background.
You can change the default AOI colour for all new AOIs in your user preferences.
Deleting an AOI
- 1
Unlock the AOI if it's locked.
- 2
Click the trash button on the AOI's row.
- 3
The AOI is removed from the list and from the canvas immediately. There's no confirmation — be sure before you click.
If you delete every AOI on a drawing, Stage 1 won't run — re-create at least one before pressing Submit.
Auto-detected vs manual AOIs
ZeroCount distinguishes two kinds:
- Auto-detected — placed automatically by the OCR pass when the drawing first opens. Adjustable like any AOI.
- Manual — drawn by you. See Manual AOIs.
There's no special badge separating the two in the list — once placed, they behave identically.