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https://github.com/intuit/AnimationEngine

Easily build advanced custom animations on iOS.
https://github.com/intuit/AnimationEngine

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Easily build advanced custom animations on iOS.

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# [![INTUAnimationEngine](https://github.com/intuit/AnimationEngine/blob/master/Images/INTUAnimationEngine.png?raw=true)](#)
[![Build Status](http://img.shields.io/travis/intuit/AnimationEngine.svg?style=flat)](https://travis-ci.org/intuit/AnimationEngine) [![Test Coverage](http://img.shields.io/coveralls/intuit/AnimationEngine.svg?style=flat)](https://coveralls.io/r/intuit/AnimationEngine) [![Version](http://img.shields.io/cocoapods/v/INTUAnimationEngine.svg?style=flat)](http://cocoapods.org/pods/INTUAnimationEngine) [![Platform](http://img.shields.io/cocoapods/p/INTUAnimationEngine.svg?style=flat)](http://cocoapods.org/pods/INTUAnimationEngine) [![License](http://img.shields.io/cocoapods/l/INTUAnimationEngine.svg?style=flat)](LICENSE)

INTUAnimationEngine makes it easy to build advanced custom animations on iOS.

INTUAnimationEngine provides a friendly interface to drive custom animations using a CADisplayLink, inspired by the UIView block-based animation API. It enables interactive animations (normally driven by user input, such as a pan or pinch gesture) to run automatically over a given duration. It can also be used to get a callback every frame of an animation.

INTUAnimationEngine includes an extensive library of easing functions that can be used to customize animation timing, as well as a complete library of interpolation functions to animate any type of value or property including those that are not animatable by Core Animation.

The project also includes a standalone spring physics library to simulate damped harmonic motion. This is used under the hood to power a spring animation API on INTUAnimationEngine that allows full control over the damping, stiffness, and mass parameters. Since the spring solver is a completely independent and generic library implemented in pure C, it can be used on its own for many other applications apart from animation.

## Installation
*INTUAnimationEngine requires iOS 5.0 or later.*

### Using [CocoaPods](http://cocoapods.org)

1. Add the pod `INTUAnimationEngine` to your [Podfile](http://guides.cocoapods.org/using/the-podfile.html).

```ruby
pod 'INTUAnimationEngine'
```

1. Run `pod install` from Terminal, then open your app's `.xcworkspace` file to launch Xcode.
1. Import the `INTUAnimationEngine.h` header. Typically, this should be written as `#import `.

#### Installing the Spring Solver Library Only
The Spring Solver used by INTUAnimationEngine is available as a standalone C library, where it can be used for other applications (including ones that are not related to animation). The Spring Solver has its own CocoaPods subspec so that it can be installed separately from the rest of the INTUAnimationEngine project. To install the Spring Solver only, add the following line to your Podfile:

```ruby
pod 'INTUAnimationEngine/SpringSolver'
```

Note that installing INTUAnimationEngine using `pod 'INTUAnimationEngine'` automatically includes the Spring Solver library as a dependency.

### Manually from GitHub

1. Download the contents of the [INTUAnimationEngine directory](INTUAnimationEngine).
1. Add all the files to your Xcode project (drag and drop is easiest).
1. Import the `INTUAnimationEngine.h` header.

## Usage
The primary difference between INTUAnimationEngine and the UIView animation methods is how the `animations` block works. With the UIView methods, the `animations` block is only executed once, and the changes made to views within this block represent the new state at the end of the animation.

With INTUAnimationEngine, the `animations` block is executed many times during the animation (once per frame), and each time it is executed, your code inside the block should update the state of views based upon the current value of the `percentage` or `progress` passed into the block. Typically, you'll want to use one of the interpolation functions included in this library to help generate all the intermediate values between the start and end states for a given property.

### Animation Engine
There are a few different API methods on INTUAnimationEngine that can be used to start an animation.

#### Without Easing (Linear)
```objc
+ (INTUAnimationID)animateWithDuration:(NSTimeInterval)duration
delay:(NSTimeInterval)delay
animations:(void (^)(CGFloat percentage))animations
completion:(void (^)(BOOL finished))completion;
```

This method will start an animation that calls the `animations` block each frame of the animation, passing in a `percentage` value that represents the animation's current percentage complete. The `completion` block will be executed when the animation completes, with the `finished` parameter indicating whether the animation was canceled.

#### With Easing
```objc
+ (INTUAnimationID)animateWithDuration:(NSTimeInterval)duration
delay:(NSTimeInterval)delay
easing:(INTUEasingFunction)easingFunction
animations:(void (^)(CGFloat progress))animations
completion:(void (^)(BOOL finished))completion;
```

This method will start an animation that calls the `animations` block each frame of the animation, passing in a `progress` value that represents the current progress of the animation (taking into account the easing function). The `easingFunction` can be any of the easing functions in [`INTUEasingFunctions.h`](INTUAnimationEngine/INTUEasingFunctions.h), or a block that defines a custom easing curve. The `completion` block will be executed when the animation completes, with the `finished` parameter indicating whether the animation was canceled.

There is also another variant of the above method that takes an `options:` parameter, which is a mask of `INTUAnimationOptions`. This can be used to repeat or autoreverse animations.

#### Using a Spring
```objc
+ (INTUAnimationID)animateWithDamping:(CGFloat)damping
stiffness:(CGFloat)stiffness
mass:(CGFloat)mass
delay:(NSTimeInterval)delay
animations:(void (^)(CGFloat progress))animations
completion:(void (^)(BOOL finished))completion;
```

This method will start a spring animation that calls the `animations` block each frame of the animation, passing in a `progress` value that represents the current progress of the animation. The animation will simulate the physics of a spring-mass system with the specified properties:

* `damping` – The amount of friction. Must be greater than or equal to zero. If exactly zero, the harmonic motion will continue indefinitely. Typical range: `1.0` to `30.0`
* `stiffness` – The stiffness of the spring. Must be greater than zero. Typical range: `1.0` to `500.0`
* `mass` – The amount of mass being moved by the spring. Must be greater than zero. Typical range: `0.1` to `10.0`

Note that the total duration of the animation is determined by simulating a spring-mass system with the above parameters until it reaches a resting state. The `completion` block will be executed when the animation completes, with the `finished` parameter indicating whether the animation was canceled.

#### Canceling Animations
```objc
+ (void)cancelAnimationWithID:(INTUAnimationID)animationID;
```

When starting an animation, you can store the returned animation ID, and pass it to the above method to cancel the animation before it completes. If the animation is canceled, the completion block will execute with `finished` parameter equal to NO.

### Easing Functions
[`INTUEasingFunctions.h`](INTUAnimationEngine/INTUEasingFunctions.h) is a library of standard easing functions. Here's a [handy cheat sheet](http://easings.net) that includes visualizations and animation demos for these functions.

### Interpolation Functions
[`INTUInterpolationFunctions.h`](INTUAnimationEngine/INTUInterpolationFunctions.h) is a library of interpolation functions.

#### Proximal Interpolation
For discrete values (where linear interpolation does not make sense), there are two proxmial interpolation functions. For example:

```objc
INTUInterpolateDiscrete(NSTextAlignmentLeft, NSTextAlignmentRight, progress)
// Returns NSTextAlignmentLeft when progress is < 0.5, NSTextAlignmentRight otherwise

[INTUInterpolateDiscreteValues(@[@(NSTextAlignmentLeft), @(NSTextAlignmentCenter), @(NSTextAlignmentRight)], progress) integerValue]
// Returns NSTextAlignmentLeft, then NSTextAlignmentCenter, and finally NSTextAlignmentRight as progress increases from 0.0 to 1.0
```

#### Linear Interpolation
For continuous values, there are a variety of linear interpolation functions. The following types are supported:

* `CGFloat`
* `CGPoint`
* `CGSize`
* `CGRect`
* `CGVector`
* `UIOffset`
* `UIEdgeInsets`
* `UIColor` / `CGColor`

There is also an untyped function `INTUInterpolate()` that takes values of type `id` and returns an interpolated value by automatically determining the type of the values. Proximal interpolation is used if the value types do not match, or if linear interpolation isn't supported for their type.

##### CGAffineTransform & CATransform3D
There are no functions that directly interpolate transforms. This is by design: linear interpolation of raw matrices often yields unexpected or invalid results. To interpolate between two transforms, decompose them into their translation, rotation, and scale components:

```objc
CGFloat rotation = INTUInterpolateCGFloat(0.0, M_PI, progress);
view.transform = CGAffineTransformMakeRotation(rotation);
// view will rotate from upright (progress = 0.0) to upside down (progress = 1.0)
```

You can concatenate transforms to combine them:

```objc
CGFloat rotation = INTUInterpolateCGFloat(0.0, M_PI, progress);
CGFloat scale = INTUInterpolateCGFloat(1.0, 0.5, progress);
view.transform = CGAffineTransformConcat(CGAffineTransformMakeScale(scale, scale), CGAffineTransformMakeRotation(rotation));
// view will rotate from upright and full size (progress = 0.0), to upside down and half size (progress = 1.0)
```

##### UIColor / CGColor
When interpolating between two colors, both colors must be in the same color space (grayscale, RGB, or HSB). Interpolating between colors in the HSB color space will generally yield better visual results than the RGB color space.

```objc
[UIColor colorWithWhite:1.0 alpha:1.0] // Grayscale color space; white
[UIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:1.0] // RGB color space; white
[UIColor colorWithHue:0.0 saturation:0.0 brightness:1.0 alpha:1.0] // HSB color space; white
```

### Spring Solver
The [SpringSolver directory](INTUAnimationEngine/SpringSolver) in the project contains a spring physics library to simulate damped harmonic motion, based on the spring solver that powers Facebook's [Pop](https://github.com/facebook/pop). The INTUAnimationEngine spring solver has been extensively refactored for simplicity and performance, and as a fully independent pure C library is highly portable to any platform and can be leveraged for other use cases beyond animation.

## Example Project
An [example project](AnimationEngineExample) is provided. It requires Xcode 6 and iOS 6.0 or later.

## Issues & Contributions
Please [open an issue here on GitHub](https://github.com/intuit/AnimationEngine/issues/new) if you have a problem, suggestion, or other comment.

Pull requests are welcome and encouraged! There are no official guidelines, but please try to be consistent with the existing code style.

## License
INTUAnimationEngine is provided under the [MIT license](LICENSE). The spring solver library within the project is provided under a [BSD license](LICENSE-SpringSolver).

# INTU on GitHub
Check out more [iOS and OS X open source projects from Intuit](https://github.com/search?utf8=✓&q=user%3Aintuit+language%3Aobjective-c&type=Repositories&ref=searchresults)!