https://github.com/psharanda/easing
Unified set of easing functions
https://github.com/psharanda/easing
easing interpolation transition
Last synced: 19 days ago
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Unified set of easing functions
- Host: GitHub
- URL: https://github.com/psharanda/easing
- Owner: psharanda
- License: mit
- Created: 2017-04-14T07:51:40.000Z (almost 9 years ago)
- Default Branch: master
- Last Pushed: 2024-06-11T23:20:56.000Z (over 1 year ago)
- Last Synced: 2025-10-19T11:02:37.613Z (4 months ago)
- Topics: easing, interpolation, transition
- Language: Swift
- Homepage:
- Size: 833 KB
- Stars: 31
- Watchers: 1
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
The Easing library is a comprehensive set of easing functions, useful for interactive transitions and other time-based calculations.
## Features
- Easy-to-use 'swifty' API to invoke calculations
- Unified [set](#reference) of easing functions
- Arbitrary cubic bezier based easings (see `.cubicBezier(...)`)
- Piecewise linear easings similar to CSS `linear()` (see `piecewiseLinear(...)`)
- Spring-based easings with physics configuration (see `spring(...)`)
- Emulate default easings from iOS (see `.caEaseIn`, `.caEaseOut`, `.caEaseInEaseOut`)
- Interpolation shorthands for commonly used types like `CGPoint`, `CGSize`, `CGAffineTransform`, `UIColor` and `UIBezierPath`
- Interactive demo app
- Extensive test coverage and fully documented
- Supports iOS 12.0+ / Mac OS X 10.13+ / tvOS 12.0+ / watchOS 4.0+ / visionOS 1.0+
## Usage
### Basic
```swift
let startValue = 20.0
let endValue = 60.0
let progress = 0.5 // Assume a progress variable that ranges from 0 to 1
let valueAtProgress = Easing.cubicEaseIn.calculate(
d1: startValue,
d2: endValue,
g: progress
)
```
### Ranges (g1/g2 and d1/d2)
`g` is the input (often time or progress). `g1`/`g2` define the input range, and `d1`/`d2` define the output range. The easing maps `g` from `[g1, g2]` to `[d1, d2]` using the chosen curve.
```swift
// Map input range to output range
let output = Easing.quadraticEaseInOut.calculate(
g1: 0,
d1: 0,
g2: 100,
d2: 1,
g: input
)
```
With `clamp: true` (default), values outside `[g1, g2]` are clamped to the nearest endpoint: for example `g = -20` behaves like `g = 0` and returns `d1`, while `g = 140` behaves like `g = 100` and returns `d2`. With `clamp: false`, those inputs will extrapolate beyond the range (e.g. `g = -20` gives a value below `d1`, `g = 140` gives a value above `d2`).
### Real world example
Imagine an interaction with a `UIScrollView` where its header is fully visible when the content offset is zero and fades out completely as the content offset exceeds 100 points. You can express this behavior with the following code in your `scrollViewDidScroll` method:
```swift
let minOffset = 0.0
let alphaForMinOffset = 0.0
let maxOffset = 100.0
let alphaForMaxOffset = 1.0
let offset = scrollView.contentOffset.y
headerView.alpha = Easing.quadraticEaseInOut.calculate(
g1: minOffset,
d1: alphaForMinOffset,
g2: maxOffset,
d2: alphaForMaxOffset,
g: offset
)
```
### Interpolatable
```swift
let startTransform = CGAffineTransform.identity
let endTransform = CGAffineTransform(scaleX: 2, y: 2)
let progress = 0.5 // Assume a progress variable that ranges from 0 to 1
view.transform = startTransform.interpolate(to: endTransform,
progress: progress,
easing: .linear)
```
### Piecewise linear (CSS `linear()` style)
CSS `linear(0, 0.25 75%, 1)` translates to:
```swift
let easing = Easing.piecewiseLinear([
PiecewiseLinearStop(0), // x defaults to 0
PiecewiseLinearStop(0.25, at: 0.75), // explicit stop position
PiecewiseLinearStop(1) // x defaults to 1
])
```
### Spring
```swift
let swiftUISpring = Easing.spring(.swiftUISpring, initialVelocity: 0)
let customSpring = Easing.spring(
mass: 1,
stiffness: 100,
damping: 10,
initialVelocity: 0,
duration: 1
)
```
## Reference
| Easing | |
| :---------------------------------------------------: | :-------------------------------------------------------------------------------------------------------------------------------------------: |
| `.linear` | 
|
| `.piecewiseLinear(0, 0.25@0.75, 1)` | 
|
| `.piecewiseLinear(spring)` | 
|
| `.spring(.swiftUISpring)` | 
|
| `.spring(.swiftUIInteractiveSpring)` | 
|
| `.spring(dampingRatio:0.7,response:0.4)` | 
|
| `.spring(response:0.5,dampingFraction:0.825)` | 
|
| `.spring(mass:1,stiffness:100,damping:10,duration:1)` | 
|
| `.smoothStep` | 
|
| `.smootherStep` | 
|
| `.quadraticEaseIn` | 
|
| `.quadraticEaseOut` | 
|
| `.quadraticEaseInOut` | 
|
| `.cubicEaseIn` | 
|
| `.cubicEaseOut` | 
|
| `.cubicEaseInOut` | 
|
| `.quarticEaseIn` | 
|
| `.quarticEaseOut` | 
|
| `.quarticEaseInOut` | 
|
| `.quinticEaseIn` | 
|
| `.quinticEaseOut` | 
|
| `.quinticEaseInOut` | 
|
| `.sineEaseIn` | 
|
| `.sineEaseOut` | 
|
| `.sineEaseInOut` | 
|
| `.circularEaseIn` | 
|
| `.circularEaseOut` | 
|
| `.circularEaseInOut` | 
|
| `.exponentialEaseIn` | 
|
| `.exponentialEaseOut` | 
|
| `.exponentialEaseInOut` | 
|
| `.elasticEaseIn` | 
|
| `.elasticEaseOut` | 
|
| `.elasticEaseInOut` | 
|
| `.backEaseIn` | 
|
| `.backEaseOut` | 
|
| `.backEaseInOut` | 
|
| `.bounceEaseIn` | 
|
| `.bounceEaseOut` | 
|
| `.bounceEaseInOut` | 
|
| `.caEaseIn` | 
|
| `.caEaseOut` | 
|
| `.caEaseInEaseOut` | 
|
| `.cubicBezier(0.11, 0.87, 0.21, -0.88)` | 
|
## Demo app
In the repo, you will find an interactive demo iOS app to experiment with different easings and discover the most suitable one for your needs.
## Integration
Use Swift Package Manager and add dependency to `Package.swift` file.
```swift
dependencies: [
.package(url: "https://github.com/psharanda/Easing.git", .upToNextMajor(from: "4.0.0"))
]
```
Alternatively, in Xcode select `File > Add Package Dependencies…` and add Easing repository URL:
```
https://github.com/psharanda/Easing.git
```
## References
The main set of easing functions is a Swift port of https://github.com/warrenm/AHEasing and https://github.com/ai/easings.net
`CubicBezierInterpolator` is a Swift port of `nsSMILKeySpline` code from Mozilla https://github.com/mozilla-services/services-central-legacy/blob/master/content/smil/nsSMILKeySpline.cpp
## Contributing
We welcome contributions! If you find a bug, have a feature request, or want to contribute code, please open an issue or submit a pull request.
## License
Easing is available under the MIT license. See the LICENSE file for more info.