WolfDan/swift-jpeg

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

jpeg

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 Apache 2.0 License. The example programs are public domain and can be adapted freely.

documentation · license

Requirements

The swift-jpeg library requires Swift 5.10 or later.

Platform	Status
🐧 Linux
🍏 Darwin
🍏 Darwin (iOS)
🍏 Darwin (tvOS)
🍏 Darwin (visionOS)
🍏 Darwin (watchOS)

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 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),
        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
    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
    ])
}