Operators

# inner_circle (Operator)

## Name

inner_circle — Largest inner circle of a region.

## Signature

inner_circle(Regions : : : Row, Column, Radius)

## Description

The operator inner_circle determines the largest inner circle of a region. This is the biggest discrete circle region that completely fits into the region. For this circle the center (Row, Column) and the radius (Radius) are calculated. If the position of the circle is ambiguous, the "first possible" position (as far upper left as possible) is returned.

In the documentation of this chapter (Regions / Features), you can find an image illustrating regions with varying inner circles.

The output of the operator is chosen in such a way that it can be used as an input for the operators disp_circle, gen_circle, and gen_ellipse_contour_xld.

If several regions are passed in Regions corresponding tuples are returned as output parameters. In case of an empty input region all parameters have the value 0.0 if no other behavior was set with set_system.

## Attention

If several inner circles are present at a region only the most upper left solution is returned.

## Parallelization

• Multithreading type: reentrant (runs in parallel with non-exclusive operators).
• Automatically parallelized on tuple level.

## Parameters

Regions (input_object)  region(-array) object

Regions to be examined.

Row (output_control)  circle.center.y(-array) (real)

Line index of the center.

Column (output_control)  circle.center.x(-array) (real)

Column index of the center.

## Example (HDevelop)

```read_image(Image,'fabrik')
regiongrowing(Image,Seg,5,5,6,100)
select_shape(Seg,H,'area','and',100,2000)
dev_set_draw('margin')
dev_display(Circles)
```

## Complexity

If F is the area of the region and R is the radius of the inner circle the runtime complexity is O(sqrt(F) * R).

## Result

The operator inner_circle returns the value 2 (H_MSG_TRUE) if the input is not empty. The behavior in case of empty input (no input regions available) is set via the operator set_system('no_object_result',<Result>), the behavior in case of empty region is set via set_system('empty_region_result',<Result>). If necessary an exception is raised.