🦋   swift-jpeg   🦋

a cross-platform pure Swift framework for decoding, inspecting, editing, and encoding JPEG images

documentation · license

Requirements

The core framework has no external dependencies, including Foundation, and should compile and provide consistent behavior on all Swift platforms. The framework supports additional features, such as file system support, on Linux and MacOS.

The swift-jpeg library requires Swift 6.0 or later.

Platform	Status
💬 Documentation
🐧 Linux
🐧 Linux (musl)
🍏 Darwin
🍏 Darwin (iOS)
🍏 Darwin (tvOS)
🍏 Darwin (visionOS)
🍏 Darwin (watchOS)
🤖 Android

Check deployment minimums

tutorials and example programs

• basic decoding
• basic encoding
• advanced decoding
• advanced encoding
• using in-memory images
• online decoding
• requantizing images
• lossless rotations
• custom color formats

api reference

• JPEG.JPEG
• JPEG.General
• JPEG.System

getting started

To use swift-jpeg in a project, add this descriptor to the dependencies list in your Package.swift:

.package(url: "https://github.com/tayloraswift/swift-jpeg", from: "2.0.0")

basic usage

Decode an image:

import JPEG

func decode(jpeg path: String) throws {
    guard
    let image: JPEG.Data.Rectangular<JPEG.Common> = try .decompress(path: path) else {
        // failed to access file from file system
    }

    let rgb: [JPEG.RGB] = image.unpack(as: JPEG.RGB.self)
    let size: (x:Int, y:Int) = image.size
    // ...
}

Encode an image:

import JPEG

func encode(
    jpeg path: String,
    size: (x:Int, y:Int),
    pixels rgb: [JPEG.RGB],
    compression: Double, // 0.0 = highest quality
) throws {
    let layout: JPEG.Layout<JPEG.Common> = .init(
        format: .ycc8,
        process: .baseline,
        components: [
            1: (factor: (2, 2), qi: 0), // Y
            2: (factor: (1, 1), qi: 1), // Cb
            3: (factor: (1, 1), qi: 1), // Cr
        ],
        scans: [
            .sequential((1, \.0, \.0), (2, \.1, \.1), (3, \.1, \.1)),
        ]
    )
    let jfif: JPEG.JFIF = .init(version: .v1_2, density: (72, 72, .inches))
    let image: JPEG.Data.Rectangular<JPEG.Common> = .pack(
        size: size,
        layout: layout,
        metadata: [.jfif(jfif)],
        pixels: rgb
    )

    try image.compress(
        path: path,
        quanta: [
            0: JPEG.CompressionLevel.luminance(compression).quanta,
            1: JPEG.CompressionLevel.chrominance(compression).quanta
        ]
    )
}