Mantis

Mantis is an iOS Image cropping library, which mimics the Photo App written in Swift and provides rich cropping interactions for your iOS/Mac app (Catalyst only).

🆕 What's New

Perspective Correction (Skew)

Mantis now supports Apple Photos–style perspective correction, allowing users to adjust horizontal and vertical skew in addition to straightening. When enabled, the slide dial displays three circular icon buttons — Straighten, Vertical, and Horizontal — letting users switch between adjustment modes with a single tap.

• Real-time 3D perspective preview powered by CATransform3D
• Accurate image export using CIPerspectiveCorrection
• Full integration with existing features: undo/redo, flip, 90° rotation, and preset transformations

Appearance Mode

Mantis now supports light, dark, and system appearance modes. By default Mantis uses a dark appearance (backward compatible). You can switch to a light theme or let it follow the system setting.

• .forceDark — Always dark (default)
• .forceLight — Always light, similar to Apple Photos in light mode
• .system — Follows the system light/dark mode setting

var config = Mantis.Config()
config.appearanceMode = .forceLight   // or .system
let cropViewController = Mantis.cropViewController(image: <Your Image>, config: config)

Demos

ScreenRecording_02-24-2026.2-37-35.AM_1.MP4

Mantis also provides rich crop shapes from the basic circle/square to polygon to arbitrary paths(We even provide a heart shape ❤️ 😏).

Requirements

• iOS 12.0+
• MacOS 10.15+
• Xcode 10.0+

Install

CocoaPods

pod 'Mantis', '~> 2.29.0'

Carthage

github "guoyingtao/Mantis"

Swift Packages

• Repository: https://github.com/guoyingtao/Mantis.git
• Rules: Version - Exact - 2.29.0

Usage

Basic

• Create a CropViewController from Mantis with default config

You need set (cropViewController or its navigation controller).modalPresentationStyle = .fullscreen for iOS 13+ when the cropViewController is presented

UIKit

    let cropViewController = Mantis.cropViewController(image: <Your Image>)
    cropViewController.delegate = self
    <Your ViewController>.present(cropViewController, animated: true)

SwiftUI

• Create an ImageCropperView from Mantis with default config

struct MyView: View {
    @State private var image: UIImage?
    @State private var transformation: Transformation?
    @State private var cropInfo: CropInfo?

    var body: some View {
        ImageCropperView(
            image: $image,
            transformation: $transformation,
            cropInfo: $cropInfo
        )
    }
}

Note:

• To start a crop operation programmatically, use the existing action binding(for ImageCropperView):

  action = .crop

• To receive the result of the crop (success or failure), use the new onCropCompleted callback.
  This is especially useful because cropping may not complete instantly in all cases, so relying on this callback ensures you update your UI only after the operation finishes.

• The caller needs to conform CropViewControllerDelegate

public protocol CropViewControllerDelegate: class {
    func cropViewControllerDidCrop(_ cropViewController: CropViewController, cropped: UIImage, transformation: Transformation, cropInfo: CropInfo)
    func cropViewControllerDidCancel(_ cropViewController: CropViewController, original: UIImage)
    
    // The implementation of the following functions are optional
    func cropViewControllerDidFailToCrop(_ cropViewController: CropViewController, original: UIImage)     
    func cropViewControllerDidBeginResize(_ cropViewController: CropViewController)
    func cropViewControllerDidEndResize(_ cropViewController: CropViewController, original: UIImage, cropInfo: CropInfo)    
}

CropToolbar mode

• CropToolbar has two modes:

  • normal mode

  In normal mode, you can use a set of standard CropViewController photo editing features with "Cancel" and "Done" buttons.

let cropViewController = Mantis.cropViewController(image: <Your Image>)

• embedded mode

This mode does not include "Cancel" and "Done" buttons, so you can embed CropViewController into another view controller

var config = Mantis.Config()
config.cropToolbarConfig.mode = .embedded
let cropViewController = Mantis.cropViewController(image: <Your Image>, config: config)

Add your own ratio

            // Add a custom ratio 1:2 for portrait orientation
            let config = Mantis.Config()
            config.addCustomRatio(byVerticalWidth: 1, andVerticalHeight: 2)            
            <Your Crop ViewController> = Mantis.cropViewController(image: <Your Image>, config: config)
            
            // Set the ratioOptions of the config if you don't want to keep all default ratios
            let config = Mantis.Config() 
            //config.ratioOptions = [.original, .square, .custom]
            config.ratioOptions = [.custom]
            config.addCustomRatio(byVerticalWidth: 1, andVerticalHeight: 2)            
            <Your Crop ViewController> = Mantis.cropViewController(image: <Your Image>, config: config)

• If you always want to use only one fixed ratio, set Mantis.Config.presetFixedRatioType = alwaysUsingOnePresetFixedRatio

    <Your Crop ViewController>.config.presetFixedRatioType = .alwaysUsingOnePresetFixedRatio(ratio: 16.0 / 9.0)

When choose alwaysUsingOnePresetFixedRatio, fixed-ratio setting button does not show.

• If you want to hide rotation control view, set Mantis.Config.cropViewConfig.showAttachedRotationControlView = false
• If you want to use ratio list instead of presenter, set Mantis.CropToolbarConfig.ratioCandidatesShowType = .alwaysShowRatioList

public enum RatioCandidatesShowType {
    case presentRatioList
    case alwaysShowRatioList
}

• If you build your custom toolbar you can add your own fixed ratio buttons

// set a custom fixed ratio
cropToolbarDelegate?.didSelectRatio(ratio: 9 / 16)

Crop shapes

• If you want to set different crop shape, set Mantis.Config.cropViewConfig.cropShapeType

public enum CropShapeType {
    case rect
    case square
    case ellipse
    case circle(maskOnly: Bool = false)
    case diamond(maskOnly: Bool = false)
    case heart(maskOnly: Bool = false)
    case polygon(sides: Int, offset: CGFloat = 0, maskOnly: Bool = false)
    case path(points: [CGPoint], maskOnly: Bool = false)
}

Preset transformations

• If you want to apply transformations when showing an image, set Mantis.Config.cropViewConfig.presetTransformationType

public enum PresetTransformationType {
    case none
    case presetInfo(info: Transformation)
    case presetNormalizedInfo(normalizedInfo: CGRect)
}

Please use the transformation information obtained previously from delegate method cropViewControllerDidCrop(_ cropViewController: CropViewController, cropped: UIImage, transformation: Transformation, , cropInfo: CropInfo).

Undo/Redo Support

• Mantis offers full support for Undo, Redo, Revert to Original in both iOS and Catalyst.

• If you want to add support for this feature, set Mantis.Config.enableUndoRedo = true

• Catalyst menus for this feature are localized.

Perspective Correction (Skew) 🆕

• Enable perspective correction to let users adjust horizontal and vertical skew, similar to the Apple Photos app.

var config = Mantis.Config()
config.cropViewConfig.enablePerspectiveCorrection = true
let cropViewController = Mantis.cropViewController(image: <Your Image>, config: config)

When enablePerspectiveCorrection is true, the slide dial is used by default (no need to set builtInRotationControlViewType explicitly) and automatically switches to withTypeSelector mode, showing three circular icon buttons (Straighten / Vertical / Horizontal) above the ruler. Users can tap each button to switch adjustment modes.

• The skew values are included in the Transformation and CropInfo returned by the delegate, so you can persist and restore them via presetTransformationType.

• You can optionally customize the appearance of the type selector buttons through SlideDialConfig:

  • typeButtonSize — diameter of each circular button (default: 48)
  • typeButtonSpacing — spacing between buttons (default: 16)
  • activeColor — color for the selected button ring and value text
  • inactiveColor — color for unselected buttons
  • pointerColor — color of the center pointer on the ruler
  • skewLimitation — maximum skew angle in degrees (default: 30)

Appearance Mode 🆕

• Set the appearance mode to control the overall look of the crop UI.

var config = Mantis.Config()
config.appearanceMode = .forceLight   // or .forceDark (default), .system
let cropViewController = Mantis.cropViewController(image: <Your Image>, config: config)

public enum AppearanceMode {
    /// Always use dark appearance (default, backward compatible)
    case forceDark
    /// Always use light appearance
    case forceLight
    /// Follow system light/dark mode setting
    case system
}

• .forceDark is the default, keeping the existing dark-themed behavior.
• .forceLight uses a light color scheme similar to Apple Photos in light mode.
• .system dynamically adapts to the user's system-wide light/dark mode setting.

The appearance mode affects all UI components including the toolbar, dimming overlay, rotation dial, type selector, and ratio item views.

Localization

• UIKit project
  Add more languages support to the Localizations section for Project Info tab

fig 1

• SwiftUI project
  Please check this link

• Static frameworks If you use static frameworks in CocoaPods, you need to add the code below in order to find the correct resource bundle.

    Mantis.locateResourceBundle(by: Self.self)

• Custom localization tables and bundle

By default mantis will use built in localization tables to get string resources not every language is supported out of the box (see fig 1).

However if your app support multiple languages and those languages are not 'built in', then you can define your own strings table and localize them in the application target or framework. By doing so you'll need to configure Mantis localization.

IMPORTANT! Firstly you'll need to create strings file with these keys:

"Mantis.Done" = "";
"Mantis.Cancel" = "";
"Mantis.Reset" = "";
"Mantis.Original" = "";
"Mantis.Square" = "";
"Mantis.Straighten" = "";
"Mantis.Horizontal" = "";
"Mantis.Vertical" = "";

Then you'll need to configure Mantis:

let config = Mantis.Config()
config.localizationConfig.bundle = // a bundle where strings file is located
config.localizationConfig.tableName = // a localized strings file name within the bundle

Custom View Controller

• If needed you can subclass CropViewController:

class CustomViewController: CropViewController {
    override func viewDidLoad() {
        super.viewDidLoad()

        // Do your custom logic here.
        // The MantisExample project also has a showcase for a CustomViewController.
    }
}

• To get an instance, Mantis provides a factory method:

let cropViewController: CustomViewController = Mantis.cropViewController(image: image, config: config)

Demo projects

Mantis provide two demo projects

• MantisExample (using Storyboard)
• MantisSwiftUIExample (using SwiftUI)
  • Mantis provides an out-of-the-box SwiftUI wrapper named ImageCropperView,
    making it easy to integrate the image cropping interface directly in SwiftUI apps.

Showcases

Below are apps that use the Mantis framework. If your app also uses Mantis and you’d like it to be showcased here, please submit a PR following the existing format.

Pictopoem Where Images Whisper Poems	Text Behind Me Add Depth to Your Photos

Backers & Sponsors

Become a sponsor through GitHub Sponsors.

Credits

• The crop feature is strongly inspired by TOCropViewController
• The rotation feature is inspired by IGRPhotoTweaks
• The rotation dial is inspired by 10clock
• Thanks Leo Dabus for helping me to solve the problem of cropping an ellipse image with transparent background https://stackoverflow.com/a/59805317/288724
• Icons made by Freepik from www.flaticon.com is licensed by CC 3.0 BY