Transformation | API Reference | ArcGIS Maps SDK for JavaScript 4.31

Constructors

Transformation Constructor new Transformation()

Method Overview

Return Type	Summary	Class
ErrorResult	Calculates distance errors for a transformation on a given set of the input points to the output points.	Transformation
	Flips all the `x` coordinates of geometries on the vertical y-axis (right or left) that is centered between `x0` and `x1`.	Transformation
	Flips all the `y` coordinates of geometries on the horizontal x-axis (up or down) that is centered between `y0` and `y1`.	Transformation
	Initializes a new transformation from the input and output control points.	Transformation
Boolean	Determines if the transformation is in its default state, which is an identity matrix.	Transformation
	Rotates the geometries by the specified angle in degrees around the point specified by the x and y coordinates.	Transformation
	Resizes the geometries by the specified scale factors defined by the x and y coordinates.	Transformation
	Use this method to reset the transformation to its default state, which is an identity matrix.	Transformation
	Use this method to swap the x and y coordinate values in the transformation.	Transformation
	Shifts a geometry's points by the specified proportion in parallel to the x and y directions, except those points that are along the shear axis, which is a line defined by the x and y coordinates.	Transformation
	Shifts all the coordinates of the geometries by the distance and direction between the specified `x` and `y` coordinates and their current location.	Transformation

Method Details

calculateErrors Method calculateErrors(input, output){ErrorResult}

Calculates distance errors for a transformation on a given set of the input points to the output points. This method is usually used to calculate errors for the transformation initialized by initializeFromControlPoints.

The length of the input and output arrays must be the same.

Parameters

input Point []

The input points to transform from.

output Point []

The output points to transform to.

Returns

Type	Description
ErrorResult	Returns an object representing the errors incurred during transformation.

Example

// Calculate the errors for a transformation
const errors = transformation.calculateErrors(inputPoints, outputPoints);
// Example returned object:
// { rms: 0.5, errorsOut: [0.1, 0.2, 0.3, 0.4, 0.5] }

flipX Method flipX(x0, x1)

Flips all the x coordinates of geometries on the vertical y-axis (right or left) that is centered between x0 and x1. For example, if x0 is 0 and x1 is 10, all the x coordinates of the geometries will be flipped, or mirrored, on the vertical axis centered at x = 5.

Parameters

x0 Number

The x-coordinate of the first geometry.

x1 Number

The x-coordinate of the second geometry.

Example

// Flip the x-coordinates of a geometry on the vertical axis
const transform = new Transformation();
transform.flipX(0, 10);
const result = affineTransformOperator.execute(polygon, transform);

// Flip the x-coordinates of a geometry on the vertical axis centered at the geometry's center
const centerX = polygon.extent.center.x;
transform.flipX(centerX, centerX);
const result = affineTransformOperator.execute(polygon, transform);

flipY Method flipY(y0, y1)

Flips all the y coordinates of geometries on the horizontal x-axis (up or down) that is centered between y0 and y1. For example, if y0 is 0 and y1 is 10, all the y coordinates of the geometries will be flipped, or mirrored, on the horizontal axis centered at y = 5.

Parameters

y0 Number

The y-coordinate of the first geometry.

y1 Number

The y-coordinate of the second geometry.

Example

// Flip the y-coordinates of a geometry on the vertical axis
transformation.flipY(0, 10);
const result = affineTransformOperator.execute(polygon, transform);

// Flip the y-coordinates of a geometry on the horizontal axis centered at the geometry's center
const centerY = polygon.extent.center.y;
transform.flipY(centerY, centerY);
const result = affineTransformOperator.execute(polygon, transform);

initializeFromControlPoints Method initializeFromControlPoints(type, input, output, inverseOut)

Initializes a new transformation from the input and output control points. Uses least squares method to find the best fit transformation. Adding control points allows you to snap lines and polygons to the input and output points on a map.

The length of the input and output arrays must be the same.

Parameters

type String

The type of transformation to initialize.

Value	Description
"conformal"	Preserves the angles between curves.
"general"	Preserves lines and parallelisms. Does not preserve angles or lengths.

Possible Values:"conformal"|"general"

input Point []

The input points to transform from.

output Point []

The output points to transform to.

inverseOut Transformation

optional

The transformation instance that is the inverse of the calculated transformation.

Example

// Initialize a transformation from control points
transformation.initializeFromControlPoints("conformal", inputPoints, outputPoints);

isIdentity Method isIdentity(){Boolean}

Determines if the transformation is in its default state, which is an identity matrix.

Returns

Type	Description
Boolean	Returns `true` if the transformation is the default and has not been changed. There will be no change in the geometries when applying the transformation.

See also

setIdentity()

rotate Method rotate(angleInDegrees, rotationX, rotationY)

Rotates the geometries by the specified angle in degrees around the point specified by the x and y coordinates. The point can be the center of the geometries or any other point.

Parameters

angleInDegrees Number

The angle to rotate the geometries in degrees.

rotationX Number

The x-coordinate of the point to rotate around.

rotationY Number

The y-coordinate of the point to rotate around.

Example

// Rotate a geometry
transformation.rotate(90, 0, 0);
const result = affineTransformOperator.execute(polygon, transform);

scale Method scale(x, y)

Resizes the geometries by the specified scale factors defined by the x and y coordinates. The coordinates define how much scaling is applied to the geometries in the x and y directions.

Parameters

x Number

The x-coordinate that defines the horizontal scale factor.

y Number

The y-coordinate that defines the vertical scale factor.

Example

// Scale a geometry
transformation.scale(2, 2);
const result = affineTransformOperator.execute(polygon, transform);

setIdentity Method setIdentity()

Use this method to reset the transformation to its default state, which is an identity matrix. This method is useful when reusing the class instance for multiple transformations.

See also

Wikipedia - Identity Matrix

setSwapCoordinates Method setSwapCoordinates()

Use this method to swap the x and y coordinate values in the transformation. An example usage is when slicing vertically with the polgonSlicerOperator.findSlicesByArea() method.

shear Method shear(proportionX, proportionY)

Shifts a geometry's points by the specified proportion in parallel to the x and y directions, except those points that are along the shear axis, which is a line defined by the x and y coordinates. This transformation preserves lines and parallelisms, however it may distort angles and distances. Applying this transformation will not change a geometry's area.

Parameters

proportionX Number

The proportion to shear the geometry in the x direction.

proportionY Number

The proportion to shear the geometry in the y direction.

Example

// Shear a geometry
transformation.shear(0.5, 0.5);
const result = affineTransformOperator.execute(polygon, transform);

shift Method shift(x, y)

Shifts all the coordinates of the geometries by the distance and direction between the specified x and y coordinates and their current location. This operation does not change the size or shape of the geometries.

Parameters

x Number

The x-coordinate to shift by.

y Number

The y-coordinate to shift by.

Example

// Shift the coordinates of a geometry
transformation.shift(5, 2);
const result = affineTransformOperator.execute(polygon, transform);

Type Definitions

ErrorResult Type Definition ErrorResult

Object returned from the calculateErrors() method.

Properties: rms Number

The root mean square (rms) of the 'average' distance error between the specified output points and the transformed input points.

errorsOut Number []

Contains the errors of the individual distance differences between specific pairs of points.