Operators

gen_circle (Operator)

Name

gen_circle — Create a circle.

Signature

gen_circle( : Circle : Row, Column, Radius : )

Description

The operator gen_circle generates one or more circles described by the center and Radius. If several circles shall be generated the coordinates must be passed in the form of tuples.

gen_circle only creates symmetric circles. To achieve this, the radius is internally rounded down to a multiple of 0.5. If an integer number is specified for the radius (i.e., 1, 2, 3, ...) an even diameter is obtained, and hence the circle can only be symmetric with respect to a center with coordinates that have a fractional part of 0.5. Consequently, internally the coordinates of the center are adapted to the closest coordinates that have a fractional part of 0.5. Here, integer coordinates are rounded down to the next smaller values with a fractional part of 0.5. For odd diameters (i.e., radius = 1.5, 2.5, 3.5, ...), the circle can only be symmetric with respect to a center with integer coordinates. Hence, internally the coordinates of the center are rounded to the nearest integer coordinates. It should be noted that the above algorithm may lead to the fact that circles with an even diameter are not contained in circles with the next larger odd diameter, even if the coordinates specified in Row and Column are identical.

If the circle extends beyond the image edge it is clipped to the current image format if the value of the system flag 'clip_region' is set to 'true' (set_system).

Attention

For speed reasons, the resulting region may contain additional pixels at the border and some individual pixels at the border may be missing. This may lead to an inconsistency between the operators smallest_circle and gen_circle.

Parallelization

• Multithreading type: reentrant (runs in parallel with non-exclusive operators).
• Processed without parallelization.

Parameters

Circle (output_object)  region(-array) object

Generated circle.

Row (input_control)  circle.center.y(-array) (real / integer)

Line index of center.

Default value: 200.0

Suggested values: 0.0, 10.0, 50.0, 100.0, 200.0, 300.0

Typical range of values: 1.0 ≤ Row ≤ 1024.0 (lin)

Minimum increment: 1.0

Recommended increment: 10.0

Column (input_control)  circle.center.x(-array) (real / integer)

Column index of center.

Default value: 200.0

Suggested values: 0.0, 10.0, 50.0, 100.0, 200.0, 300.0

Typical range of values: 1.0 ≤ Column ≤ 1024.0 (lin)

Minimum increment: 1.0

Recommended increment: 10.0

Default value: 100.5

Suggested values: 1.0, 1.5, 2.0, 2.5, 3, 3.5, 4, 4.5, 5.5, 6.5, 7.5, 9.5, 11.5, 15.5, 20.5, 25.5, 31.5, 50.5

Typical range of values: 1.0 ≤ Radius ≤ 1024.0 (lin)

Minimum increment: 1.0

Recommended increment: 10.0

Example (HDevelop)

```read_image(Image,'fabrik')
gen_circle(Circle,300.0,200.0,150.5)
dev_clear_window ()
```

Complexity

Storage complexity (byte): O(Radius * 8)

Result

If the parameter values are correct, the operator gen_circle returns the value 2 (H_MSG_TRUE). Otherwise an exception is raised. The clipping according to the current image format is set via the operator set_system('clip_region',<'true'/'false'>). If an empty region is created by clipping (the circle is completely outside of the image format) the operator set_system('store_empty_region',<'true'/'false'>) determines whether the empty region is put out.