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decode, inspect, edit, and encode jpeg images in pure swift


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

Swift JPEG is available under the Mozilla Public License 2.0. The example programs are public domain and can be adapted freely.

tutorials and example programs

api reference

getting started

To Swift JPEG in a project, add this descriptor to the dependencies list in your Package.swift:

.package(url: "https://github.com/kelvin13/jpeg", .exact("1.0.0")) 

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)
        // failed to access file from file system

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

Encode an image:

import JPEG
func encode(jpeg path:String, size:(x:Int, y:Int), pixels:[JPEG.RGB], 
    compression:Double) // 0.0 = highest quality
    let layout:JPEG.Layout<JPEG.Common> = .init(
        format:     .ycc8,
        process:    .baseline, 
            1: (factor: (2, 2), qi: 0), // Y
            2: (factor: (1, 1), qi: 1), // Cb
            3: (factor: (1, 1), qi: 1), // Cr 
            .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