Note: IELLIPSE creates an annotation object with an identifier of OVAL. This identifier must be used when manipulating the object with routines like ISETPROPERTY.

Note: If you create the ellipse with an anisotropic coordinate system, the resulting ellipse object might not appear as expected. If the ellipse object appears distorted, try using device input coordinates.

Examples

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In the following example, we overlay an ellipse on an interesting muscle tissue feature.

 

; Open the data         

file = FILEPATH('muscle.jpg', $        

   SUBDIRECTORY = ['examples', 'data'])        

; Create an iTool with the image data        

IIMAGE, file, TITLE = 'Muscle Tissue', IDENTIFIER = iToolID        

; Ellipse center (in data space coordinates)        

center = [238, 315]        

; Major and minor axis distances (data space coords)        

majAxisDist = 50.0        

minAxisDist = 30.0        

; Calculate the ellipse eccentricity        

eccentricity = SQRT(1 - (minAxisDist^2 / majAxisDist^2))        

; Write the ellipse to the iTool's data space        

IELLIPSE, majAxisDist, center[0], center[1], $        

   /DATA, ECCENTRICITY = eccentricity, $        

   VISUALIZATION = iToolID, THETA = 120        

; Change the ellipse's color, thickness, and transparency        

ISETPROPERTY, 'oval', THICK=3, COLOR=[240,0,0], FILL_BACKGROUND=0

Syntax

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IELLIPSE, A, X, Y [, Z] [, /DATA | , /DEVICE | , /NORMAL] [, ECCENTRICITY=Value] [, IDENTIFIER=Variable] [, PROPERTY=Value] [, TARGET_IDENTIFIER=iToolID] [, THETA=Value] [, TOOL=iToolID] [, /VISUALIZATION]

Arguments

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A

The length of the semi-major axis, specified in normalized coordinates, unless the DATA or DEVICE keyword is set.

X, Y, Z

The center point of the ellipse, specified in normalized coordinates, unless the DATA or DEVICE keyword is set.

Keywords

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Any property of an ellipse annotation can be set using this routine. To set the value of a property, specify the property name as a keyword set equal to the appropriate property value. See ISETPROPERTY for details.

DATA

Set this keyword if the input arguments are specified in data coordinates.

DEVICE

Set this keyword if the input arguments are specified in device coordinates (pixels).

ECCENTRICITY

Set this keyword to a floating-point value between 0.0 and 1.0 specifying the eccentricity of the ellipse, defined here as

where a is the length of the semi-major axis and b is the length of the semi-minor axis. If a value is not supplied, a default value of 0 (representing a circle) is used.

IDENTIFIER

Set this keyword to a named variable that will contain the full identifier of the newly-created object.

NORMAL

Set this keyword if the input arguments are specified in normalized [0, 1] coordinates (the default).

TARGET_IDENTIFIER

Set this keyword to the iTools identifier of an object that is contained in the data space into which the ellipse object should be placed. If a value is not supplied, the first data space in the current view is used.

THETA

Set this keyword to the angle (in degrees) to rotate the object.

If a single value is supplied, the ellipse is rotated counter-clockwise from horizontal.

If a three-element vector is supplied, the values define the degrees of rotation around the X, Y, and Z axis, respectively. Rotation is applied in the order of X, Y, and then Z.

If a value is not supplied, a default of 0 ([0,0,0]) is used.

Note: The coordinate system is right-handed, such that when looking from a positive axis to the origin, a positive rotation is counter-clockwise.

TOOL

Set this keyword to the iTools identifier of the iTool in which TARGET_IDENTIFIER is found. If a value is not supplied, the current iTool is used.

VISUALIZATION

Set this keyword to add the object to the data space. If this keyword is not set, the object is added to the annotation layer.

Version History

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7.1	Introduced

See Also

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IPOLYLINE, IPOLYGON, ICONVERTCOORD, ITEXT