EasyImagy：像素级图片处理工具库

EasyImagy makes it easy to process images in Swift.

var image = Image<RGBA<UInt8>>(named: "ImageName")!

print(image[x, y])
image[x, y] = RGBA(red: 255, green: 0, blue: 0, alpha: 127)
image[x, y] = RGBA(0xFF00007F) // red: 255, green: 0, blue: 0, alpha: 127

// Iterates over all pixels
for pixel in image {
    // ...
}

// Processes images (e.g. binarizations)
let binarized: Image<Bool> = image.map { $0.gray >= 127 }

// From/to `UIImage`
image = Image<RGBA<UInt8>>(uiImage: imageView.image!)
imageView.image = image.uiImage

Introduction

Processing images by CoreGraphics is complicated: various formats, old C APIs and painful memory management. EasyImagy provides easier APIs to process images.

Typically the Image type is used with the RGBA type. The RGBA is a simple structure declared as follows.

struct RGBA<Channel> {
    var red: Channel
    var green: Channel
    var blue: Channel
    var alpha: Channel
}

You can easily access to pixels using subscripts like image[x, y] and also their channels using properties red, green, blue and alpha.

In addition, Image and RGBA provide some powerful APIs to process images. For example, it is possible to convert an image to grayscale combining Image.map with RGBA.gray in one line as shown below.

let grayscale: Image<UInt8> = image.map { $0.gray }

Another notable feature of EasyImagy is that the Image is a struct, i.e. a value type, with copy-on-write. It means

Image instances never be shared
defensive copying is unnecessary
no wastful copying of Image instances
copying is executed lazily when it is required

var another = image // Not copied here because of copy-on-write
another[x, y] = RGBA(0xff0000ff) // Copied here lazily

Usage

Import

import EasyImagy

Initialization

let image = Image<RGBA<UInt8>>(named: "ImageName")!

let image = Image<RGBA<UInt8>>(contentsOfFile: "path/to/file")!

let image = Image<RGBA<UInt8>>(data: Data(/* ... */))!

let image = Image<RGBA<UInt8>>(uiImage: imageView.image!) // from a UIImage

let image = Image<RGBA<UInt8>>(width: 640, height: 480, pixels: pixels) // from pixels

let image = Image<RGBA<UInt8>>(width: 640, height: 480, pixel: .black) // a black RGBA image

let image = Image<UInt8>(width: 640, height: 480, pixel: .min) // a black grayscale image

let image = Image<Bool>(width: 640, height: 480, pixel: false) // a black binary image

Access to a pixel

// Gets a pixel by subscripts
let pixel = image[x, y]

// Sets a pixel by subscripts
image[x, y] = RGBA(0xFF0000FF)
image[x, y].alpha = 127

// Safe get for a pixel
if let pixel = image.pixelAt(x: x, y: y) {
    print(pixel.red)
    print(pixel.green)
    print(pixel.blue)
    print(pixel.alpha)
    
    print(pixel.gray) // (red + green + blue) / 3
    print(pixel) // formatted like "#FF0000FF"
} else {
    // `pixel` is safe: `nil` is returned when out of bounds
    print("Out of bounds")
}

Iteration

for pixel in image {
    ...
}

Rotation

let result = image.rotated(by: .pi) // Rotated clockwise by π

let result = image.rotated(byDegrees: 180) // Rotated clockwise by 180 degrees

// Rotated clockwise by π / 4 and fill the background with red
let result = image.rotated(by: .pi / 4, extrapolatedBy: .filling(.red))

Flip

let result = image.xReversed() // Flip Horizontally

let result = image.yReversed() // Flip Vertically

Resizing

let result = image.resizedTo(width: 320, height: 240)

let result = image.resizedTo(width: 320, height: 240,
    interpolatedBy: .nearestNeighbor) // Nearest neighbor

Crop

Slicing is executed with no copying costs.

let slice: ImageSlice<RGBA<UInt8>> = image[32..<64, 32..<64] // No copying costs
let cropped = Image<RGBA<UInt8>>(slice) // Copying is executed here

Conversion

Image can be converted by map as well as Array. Followings are the examples.

Grayscale

let result: Image<UInt8> = image.map { (pixel: RGBA<UInt8>) -> UInt8 in
    pixel.gray
}

// Shortened form
let result = image.map { $0.gray }

Binarization

let result: Image<Bool> = image.map { (pixel: RGBA<UInt8>) -> Bool in
    pixel.gray >= 128
}

// Shortened form
let result = image.map { $0.gray >= 128 }

Binarization (auto threshold)

let threshold = UInt8(image.reduce(0) { $0 + $1.grayInt } / image.count)
let result = image.map { $0.gray >= threshold }

Mean filter

let kernel = Image<Float>(width: 3, height: 3, pixel: 1.0 / 9.0)
let result = image.convoluted(kernel)

Gaussian filter

let kernel = Image<Int>(width: 5, height: 5, pixels: [
    1,  4,  6,  4, 1,
    4, 16, 24, 16, 4,
    6, 24, 36, 24, 6,
    4, 16, 24, 16, 4,
    1,  4,  6,  4, 1,
]).map { Float($0) / 256.0 }
let result = image.convoluted(kernel)

With `UIImage`

// From `UIImage`
let image = Image<RGBA<UInt8>>(uiImage: imageView.image!)

// To `UIImage`
imageView.image = image.uiImage

With `NSImage`

// From `NSImage`
let image = Image<RGBA<UInt8>>(nsImage: imageView.image!)

// To `NSImage`
imageView.image = image.nsImage

Requirements

Swift 4 or later
Xcode 9 or later

Installation

Swift Package Manager

Package.swift

// swift-tools-version:4.0
// The swift-tools-version declares the minimum version of Swift required to build this package.

import PackageDescription

let package = Package(
  ...
  dependencies: [
    .package(url: "https://github.com/koher/EasyImagy.git", from: "0.4.0-alpha"),
  ],
  targets: [
    .target(
      ...
      dependencies: [
        "EasyImagy",
      ]),
    ]
)

Carthage

Cartfile

github "koher/EasyImagy" "0.4.0-alpha.7"

Manually

Put EasyImagy.xcodeproj into your project/workspace in Xcode.
Click your project icon and select the application target and the "General" tab.
Add EasyImagy.framework to "Embedded Binaries".

License

The MIT License