# Geometric Statistics

The Geometric Statistics module adds a couple of image statistic variables centered around image geometry. These variables can then be used elsewhere in RoboRealm, for example in the conditional statement, VBScript module or exported to external programs using RoboRealm Plugins.

## Interface

1. Scope - Click on the appropriate radio button to select if you want the statistics to be generated from the entire image or from an individual blob. If you select individual blobs non-black pixels in the current image will be used to form blobs. To see the statistics for an individual blob click on the blob within the main RoboRealm GUI window. That will switch the variable(x) denotation to that particular blob.

2. Statistics - The module can produce many statistical numbers based on the current image. To reduce CPU load for those applications that only require some basic numbers you can select Basic Statistics that will produce a subset of Advanced Statistics that are faster to compute.

## Variables

**AREA** - the number of non-black (0,0,0) pixels in the current image

**ANGLE** - the orientation angle of the blob. This is calculated by determining the angle
from the center of gravity of the blob to the furthest point from that center along the blob's perimiter.

**ANGLE_ALT** - alternative orientation angle of the blob. This is calculated by determining the vector
formed by the center of gravity to the perimiter's center of gravity. If your blob has holes in it this may be a
more stable way to determine blob orientation than ANGLE.

**ANGLE_ALT_2** - alternative orientation angle of the blob. This is calculated by determining the average vector
formed from a current perimiter point to the center of gravity.

**COG_X, COG_Y** - the center of gravity of the blob

**PERIMETER** - the number of pixels that surround non black blobs

**AP_RATIO** - AREA / PERIMETER, determines how round an image is; also known as "Perimeter Equivalent Diameter".

**EQUIV_DIAMETER** - the diameter of a circle with the same area as the region. Calculated as sqrt(4*Area/pi)

**COMPACTNESS** - (PERIMETER*PERIMETER) / AREA : ratio of the square of the perimeter to the area; also known as "shape".

**COMPACTNESS_2** - sqrt(4*AREA/PI) / FERET : alternate compactness measure

**CIRCULARITY** - 4*PI*AREA/(PERIMETER*PERIMETER), measure of circularity.

**CIRCULARITY_2** - alternate measure of circularity.

**CIRCULARITY_3** - MIN_RADIUS/MAX_RADIUS : another alternate measure of circularity.

**MAX_RADIUS** - radius of enclosing circle around center of gravity

**MIN_RADIUS** - radius of enclosed circle around center of gravity

**FERET** - Feret's diameter also known as the caliper length or largest axis length: the greatest distance between any two non-zero pixels

**FERET_AREA** - FERET * BREATH; also know as Feret's bounding box

**FERET_ORIENTATION** - orientation of the Feret's diameter in degrees

**FERET_FIRST_XFERET_FIRST_Y
FERET_SECOND_XFERET_SECOND_Y** - points that makeup the Feret diameter

**BREATH** - the largest axis perpendicular to the Feret diameter

**ROUNDNESS** - 4*AREA/(Pi*(FERET*FERET)), measure of roundness

**MIN_X** - minimum bounding box x coordinate

**MIN_Y** - minimum bounding box y coordinate

**MAX_X** - maximum bounding box x coordinate

**MAX_Y** - maximum bounding box y coordinate

**EXTENT** - proportion of the pixels in the bounding box that are also in the region. Calculated as (blob area / bounding box area).

**
TOP_LEFT_X
TOP_LEFT_Y
TOP_RIGHT_X
TOP_RIGHT_Y
RIGHT_TOP_X
RIGHT_TOP_Y
RIGHT_BOTTOM_X
RIGHT_BOTTOM_Y
BOTTOM_LEFT_X
BOTTOM_LEFT_Y
BOTTOM_RIGHT_X
BOTTOM_RIGHT_Y
LEFT_TOP_X
LEFT_TOP_Y
LEFT_BOTTOM_X
LEFT_BOTTOM_Y** -
the extrema points of the image

**FERET_ASPECT_RATIO** - FERET/BREATH

**BOX_ASPECT_RATIO** - (MAX_X-MIN_X)/(MAX_Y-MIN_Y)

**WIDTH** - the width of the object in pixels

**HEIGHT** - the height of the object in pixels

Note that you can highlight the appropriate statistics and press CTRL-C to copy the information to your clipboard. This information can then be pasted into Excel or other statistics programs.

## See Also

Center of Gravity

Moments of Inertia

Color Statistics

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