ClipperJS

Clipper abstraction layer (simplified API)

Target of this library is to remove complexity and create an overall cleaner, JavaScript idiomatic API for Clipper.

When using this API one class, Shape, is used. Shape is a collection of paths that are all collectively closed or open. Shapes with holes are defined as multiple closed paths where the outlines are clockwise and the holes are counter-clockwise. Shapes has multiple functions that can be used to for instance compute complex boolean operations from one just call.

The next two code examples show a simple Boolean operation in clipper and in ClipperJS. Both use two predefined paths

const subjectPaths = [[{ X: 30, Y: 30 }, { X: 10, Y: 30 }, { X: 10, Y: 10 }, { X: 30, Y: 10 }]];
const clipPaths = [[{ X: 20, Y: 20 }, { X: 0, Y: 20 }, { X: 0, Y:0 }, { X: 20, Y: 0 }]];

A boolean intersect operation in clipper looks like this

const result = new ClipperLib.Paths();
const clipper = new ClipperLib.Clipper();
clipper.AddPaths(subjectPaths, ClipperLib.PolyType.ptSubject, true);
clipper.AddPaths(clipPaths, ClipperLib.PolyType.ptClip, true);
clipper.Execute(ClipperLib.ClipType.ctIntersection, result);

// result = [[{ X: 20, Y: 20 }, { X: 10, Y: 20 }, { X: 10, Y: 10 }, { X: 20, Y: 10 }]]

In ClipperJS

const subject = new Shape(subjectPaths, true);
const clip = new Shape(subjectPaths, true);

const result = subject.intersect(clip);

// result = { closed: true, paths: [[{ X: 20, Y: 20 }, { X: 10, Y: 20 }, { X: 10, Y: 10 }, { X: 20, Y: 10 }]] }

Usage

Using JSPM (ECMAScript / ES6 Module)

Install the library.

jspm install github:Doodle3D/clipper-js

Include the library.

import Shape from 'Doodle3D/clipper-js';

Using NPM (CommonJS module)

Install the library.

npm install @doodle3d/clipper-js --save

Include the library.

var Shape = require('clipper-js');

API

Shape

Shape accepts 3 optional arguments, paths, closed and capitalConversion. paths can be be devined with both upper case and lower case. Clipper only uses uppercase properties, when input is given with lower case captalConversion needs to be set to true.

new Shape([ paths = [], closed = true, capitalConversion = false, integerConversion = false, removeDuplicates = false ])

paths = [...[...{ X: Number, Y: Number }] || [...[...{ x: Number, y: Number }]
paths = Array
closed = Bool
capitalConversion = Bool
integerConversion = Bool
removeDuplicates = Bool

• paths: the paths that make up the shape
• closed: Shape is a polygon or line
• capitalConversion: converts lower case x and y to uppercase X and Y
• integerConversion: clipper only works with intergers, sometimes when input is in floats clipper fails
• removeDuplicates: clipper sometimes fails when there are duplicate points in the data set, this argument filters out all the duplicate points

Note: due to the nature of Clipper, some functions are destructive and some are non-destructive.

Boolean operation: Union

Shape = Shape.union( clipShape: Shape )

• clipShape: clip of the boolean operation

Boolean operation: Difference

Shape = Shape.difference( clipShape: Shape )

• clipShape: clip of the boolean operation

Boolean operation: Intersect

Shape = Shape.intersect( clipShape: Shape )

• clipShape: clip of the boolean operation

Boolean operation: Xor

Shape = Shape.xor( clipShape: Shape )

• clipShape: clip of the boolean operation

Offset

Shape = Shape.offset( offset: Number, options: {
  jointType = 'jtSquare',
  endType = 'etClosedPolygon',
  miterLimit = 2.0,
  roundPrecision = 0.25
} )

• offset: clip off the boolean operation
• options: optional arguments with default values
  • jointType: join type of the offset
  • endType: end type of the offset
  • mitterLimit: mitter limit
  • roundPrecision: arc tolerance

offsets the shape along its normal.

Scale Up

Shape.scaleUp( factor: Number )

scale up with factor.

Note: destructive

Scale Down

Shape.scaleDown( factor: Number )

scale up with factor.

Note: destructive

First Point

{ X: Number, Y: Number } || { x: Number, y: Number } = Shape.firstPoint([ capitalConversion: false ])

• capitalConversion: converts uppercase X and Y to lowercase x and y.

returns position of the first point.

Last Point

{ X: Number, Y: Number } || { x: Number, y: Number } = Shape.lastPoint([ capitalConversion: false ])

• capitalConversion: converts uppercase X and Y to lowercase x and y.

returns position of the last point.

Total Area

Number = Shape.totalArea()

returns total area of the shape.

Area

Number = Shape.area( index: Int )

• index: index of the sub shape

returns area of the sub shape (negative if counter-clock wise).

Areas

[...Number] = Shape.areas()

returns array of areas of all sub shapes.

Total Perimeter

Number = Shape.totalPerimeter()

returns total perimeter of the shape.

Perimeter

Number = Shape.perimeter( index: Int )

• index: index of the sub shape

returns perimeter of the sub shape.

Perimeters

[...Number] = Shape.perimeters()

returns array of perimeters of all sub shapes.

Reverse

Shape.reverse()

reverses the order of all sub shapes.

Treshold Area

Shape.tresholdArea( minArea: Number )

• minArea: minimal size of area

removes all sub shapes from shape which are smaller then min area.

Join

Shape.join( shape )

joins shape with given shape.

Note: destructive

Clone

Shape = Shape.clone()

returns copy of shape.

Shape Bounds

{
  left: Int,
  right: Int,
  top: Int,
  bottom: Int,
  width: Int,
  height: Int,
  size: Int
} = Shape.shapeBounds()

returns bounding box of shape.

Path Bounds

{
  left: Int,
  right: Int,
  top: Int,
  bottom: Int,
  width: Int,
  height: Int,
  size: Int
} = Shape.pathBounds( index: Int )

returns bounding box of sub shape.

Clean

Shape = Shape.clean( cleanDelta: Number )

Orientation

Bool = Shape.orientation( index: Int )

returns orientation of the sub shape. True if clockwise, false if counter clock wise.

Point In Shape

Bool = Shape.pointInShape( { X: Number, Y: Number }, [ capitalConversion = false, integerConversion = false ] )

• point: position used for hit detection
• capitalConversion: converts lower case x and y to uppercase X and Y
• integerConversion: converts point to intpoint

returns if point is in shape.

Point In Path

Bool = Shape.pointInPath( index: Int, { X: Number, Y: Number }, [ capitalConversion = false, integerConversion = false ] )

• point: position used for hit detection
• index: index of sub shape
• capitalConversion: converts lower case x and y to uppercase X and Y
• integerConversion: converts point to intpoint

returns if point is in sub shape.

Fix Orientation

Shape.fixOrientation()

when given path with holes, outline must be clockwise and holes must be counter-clockwise. Tries to fix the orientation.

Note: destructive

Simplify

Shape = Shape.simplify(fillType: String)

Simplifies shape using filltype. Only works for closed shapes.

Separate Shapes

[...Shape] = Shape.separateShapes()

when using union operations multiple shapes can be created. Separate Shapes splits these shapes into separate instances. All shapes keep their holes.

Round

Shape = Shape.round()

Returns new instance of Shape with all points rounded to Integers.

Remove Duplicates

Shape = Shape.removeDuplicates()

Returns new instance of Shape with all duplicate points removed.

Map To Lower

[...[...{ x: Number, y: Number }]] = Shape.mapToLower()

returns paths array with lower case x and y.