Objects
An object is the result of an image classification step. It represents a quantified region of interest (ROI) extracted from an image plane and stored in the results database.
Every object is assigned to exactly one object class. Together with the class assignment, a set of geometric and intensity metrics is calculated and stored.
Object Metrics Overview
See Metrics for the full table of available measurements.
Area Size
The count of non-black pixels inside the object boundary. Unit: px².
Perimeter
The boundary length of the object. The algorithm counts straight edges as 1 pixel and corner transitions as √2 pixels.
$$ P = \text{boundary length} - (2 - \sqrt{2}) \times \text{non-adjacent corners} $$
Circularity
How closely the object resembles a circle. Range: 0 (linear) to 1 (perfect circle).
$$ c = \frac{4\pi \cdot \text{AreaSize}}{P^2} $$
Centroid (Position)
The geometrical centre of the object, calculated from first-order spatial moments:
$$ c_x = \frac{m_{10}}{m_{00}}, \quad c_y = \frac{m_{01}}{m_{00}} $$
Bounding Box
The smallest axis-aligned rectangle that contains all pixels of the object.
Confidence
- Threshold segmentation — the threshold value that was used to extract the object. Range: 0–65535.
Solidity, Aspect Ratio, Eccentricity, Feret Diameter
Additional shape descriptors available as filter criteria in Classify ROIs.
Object Identifiers
Object ID
A unique integer ID assigned to each object during a run, starting at 1. The ID is consistent within a single results file and is displayed in the results table when enabled.
Use the With object ID option in Save Image to annotate the ID alongside the object in control images.
Parent Object ID {#parent-object-id}
EVAnalyzer supports a parent–child hierarchy between objects. When Classify ROIs or Colocalization is configured to intersect objects, the parent object ID of the child is set to the object ID of the containing parent.
An object can have at most one parent.
Example hierarchy:
- A cell object contains a nucleus.
- The nucleus’s parent object ID is the cell’s object ID.
- A spot inside the nucleus has the nucleus’s object ID as its parent.
Origin Object ID
When an object is duplicated (via a copy operation in Classify ROIs or Colocalization), the new object records the origin object’s ID. The origin ID propagates through further duplications.
Tracking ID
Links objects that represent the same physical instance across different image channels or time frames. All objects sharing a tracking ID can be compared side by side in the results table.
Tracking IDs are assigned by the Colocalization command.
Distance
EVAnalyzer calculates Euclidean distances between pairs of objects:
| Measurement | Description |
|---|---|
| Centre-to-centre | Distance between the two centroids |
| Centre-to-surface (min) | Shortest distance from one centroid to the other object’s boundary |
| Centre-to-surface (max) | Longest distance from one centroid to the other object’s boundary |
| Surface-to-surface (min) | Shortest distance between the two boundaries |
| Surface-to-surface (max) | Longest distance between the two boundaries |
$$ d = \sqrt{(x_2-x_1)^2 + (y_2-y_1)^2} $$
See Distance Transform for how to measure distances.
Intersection Count
The number of objects from another class that overlap with this object. Used as a filter criterion in Classify ROIs and as input to Colocalization.