imageFromBitmap.swift

// Note this code was correct when written (for Swift 1.0 most likely).
// Swift has evolved and Phill Apley has provided an updated version in the comments.

public struct PixelData {
    var a:UInt8 = 255
    var r:UInt8
    var g:UInt8
    var b:UInt8
}

private let rgbColorSpace = CGColorSpaceCreateDeviceRGB()
private let bitmapInfo:CGBitmapInfo = CGBitmapInfo(CGImageAlphaInfo.PremultipliedFirst.toRaw())

public func imageFromARGB32Bitmap(pixels:[PixelData], width:UInt, height:UInt)->UIImage {
    let bitsPerComponent:UInt = 8
    let bitsPerPixel:UInt = 32
    
    assert(pixels.count == Int(width * height))
    
    var data = pixels // Copy to mutable []
    let providerRef = CGDataProviderCreateWithCFData(
            NSData(bytes: &data, length: data.count * sizeof(PixelData))
        )

    let cgim = CGImageCreate(
            width,
            height,
            bitsPerComponent,
            bitsPerPixel,
            width * UInt(sizeof(PixelData)),
            rgbColorSpace,
            bitmapInfo,
            providerRef,
            nil,
            true,
            kCGRenderingIntentDefault
        )
    return UIImage(CGImage: cgim)
}