Create CGContext (then images) from raw pixel data

img@10x.png

RGBACGContext.swift

import QuartzCore

extension CGContext {
    private static let colorSpace = CGColorSpaceCreateDeviceRGB()

    private static let bitmapInfo =
        CGBitmapInfo.byteOrder32Big.rawValue |
        CGImageAlphaInfo.premultipliedLast.rawValue & CGBitmapInfo.alphaInfoMask.rawValue

    static func from(pixels: [UInt32], width: Int) -> CGContext? {
        var mutPixels = pixels
        let mutBufPtr = UnsafeMutableBufferPointer(start: &mutPixels, count: pixels.count)

        let height = pixels.count / width
        let bytesPerRow = width * 4

        return CGContext(data: mutBufPtr.baseAddress, width: width, height: height, bitsPerComponent: 8, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo: bitmapInfo, releaseCallback: nil, releaseInfo: nil)
    }
}

UIKit_CoreGraphics_Image_From_PIxels.swift

import UIKit

//              0xAABBGGRR
let b: UInt32 = 0xffff0000
let g: UInt32 = 0xff00ff00
let y: UInt32 = 0xff00ffff

let px = [
    b, b, y, y,
    b, b, b, y,
    g, g, b, b,
    g, g, g, g,
]

if let ctx = CGContext.from(pixels: px, width: 4), let cgImage = ctx.makeImage() {
    
    let uiImage = UIImage(cgImage: cgImage)
}