Swift 中的像素數組到 UIImage

Question

我一直在試圖弄清楚如何在 Swift 中將 rgb 像素數據數組轉換為 UIImage。

我將每個像素的 rgb 數據保存在一個簡單的結構中：

public struct PixelData {
   var a: Int
   var r: Int
   var g: Int
   var b: Int
}

我已經使用了以下功能，但生成的圖像不正確：

func imageFromARGB32Bitmap(pixels:[PixelData], width: Int, height: Int)-> UIImage {
    let rgbColorSpace = CGColorSpaceCreateDeviceRGB()
    let bitmapInfo:CGBitmapInfo = CGBitmapInfo(CGImageAlphaInfo.PremultipliedFirst.rawValue)
    let bitsPerComponent:Int = 8
    let bitsPerPixel:Int = 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 * Int(sizeof(PixelData)),
        rgbColorSpace,
        bitmapInfo,
        providerRef,
        nil,
        true,
        kCGRenderingIntentDefault
    )
    return UIImage(CGImage: cgim)!
}

關於如何將 rgb 數組正確轉換為 UIImage 的任何提示或指示？

Answer 1

注意：這是 iOS 創建UIImage的解決方案。 有關 macOS 和NSImage的解決方案，請參閱此答案。

您唯一的問題是PixelData結構中的數據類型需要為UInt8 。 我在 Playground 中創建了一個測試圖像，如下所示：

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

var pixels = [PixelData]()

let red = PixelData(a: 255, r: 255, g: 0, b: 0)
let green = PixelData(a: 255, r: 0, g: 255, b: 0)
let blue = PixelData(a: 255, r: 0, g: 0, b: 255)

for _ in 1...300 {
    pixels.append(red)
}
for _ in 1...300 {
    pixels.append(green)
}
for _ in 1...300 {
    pixels.append(blue)
}

let image = imageFromARGB32Bitmap(pixels: pixels, width: 30, height: 30)

---

Swift 4 更新：

我更新了imageFromARGB32Bitmap以使用 Swift 4。該函數現在返回一個UIImage? 如果出現任何問題， guard用於返回nil 。

func imageFromARGB32Bitmap(pixels: [PixelData], width: Int, height: Int) -> UIImage? {
    guard width > 0 && height > 0 else { return nil }
    guard pixels.count == width * height else { return nil }

    let rgbColorSpace = CGColorSpaceCreateDeviceRGB()
    let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedFirst.rawValue)
    let bitsPerComponent = 8
    let bitsPerPixel = 32

    var data = pixels // Copy to mutable []
    guard let providerRef = CGDataProvider(data: NSData(bytes: &data,
                            length: data.count * MemoryLayout<PixelData>.size)
        )
        else { return nil }

    guard let cgim = CGImage(
        width: width,
        height: height,
        bitsPerComponent: bitsPerComponent,
        bitsPerPixel: bitsPerPixel,
        bytesPerRow: width * MemoryLayout<PixelData>.size,
        space: rgbColorSpace,
        bitmapInfo: bitmapInfo,
        provider: providerRef,
        decode: nil,
        shouldInterpolate: true,
        intent: .defaultIntent
        )
        else { return nil }

    return UIImage(cgImage: cgim)
}

---

使其成為 UIImage 的便利初始化程序：

這個函數可以很好地作為UIImage的convenience初始化器。 這是實現：

extension UIImage {
    convenience init?(pixels: [PixelData], width: Int, height: Int) {
        guard width > 0 && height > 0, pixels.count == width * height else { return nil }
        var data = pixels
        guard let providerRef = CGDataProvider(data: Data(bytes: &data, count: data.count * MemoryLayout<PixelData>.size) as CFData)
            else { return nil }
        guard let cgim = CGImage(
            width: width,
            height: height,
            bitsPerComponent: 8,
            bitsPerPixel: 32,
            bytesPerRow: width * MemoryLayout<PixelData>.size,
            space: CGColorSpaceCreateDeviceRGB(),
            bitmapInfo: CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedFirst.rawValue),
            provider: providerRef,
            decode: nil,
            shouldInterpolate: true,
            intent: .defaultIntent)
        else { return nil }
        self.init(cgImage: cgim)
    }
}

下面是它的用法示例：

// Generate a 500x500 image of randomly colored pixels

let height = 500
let width = 500

var pixels: [PixelData] = .init(repeating: .init(a: 0, r: 0, g: 0, b: 0), count: width * height)
for index in pixels.indices {
    pixels[index].a = 255
    pixels[index].r = .random(in: 0...255)
    pixels[index].g = .random(in: 0...255)
    pixels[index].b = .random(in: 0...255)
}
let image = UIImage(pixels: pixels, width: width, height: height)

Answer 2

Swift 3 更新

struct PixelData {
    var a: UInt8 = 0
    var r: UInt8 = 0
    var g: UInt8 = 0
    var b: UInt8 = 0
}

func imageFromBitmap(pixels: [PixelData], width: Int, height: Int) -> UIImage? {
    assert(width > 0)

    assert(height > 0)

    let pixelDataSize = MemoryLayout<PixelData>.size
    assert(pixelDataSize == 4)

    assert(pixels.count == Int(width * height))

    let data: Data = pixels.withUnsafeBufferPointer {
        return Data(buffer: $0)
    }

    let cfdata = NSData(data: data) as CFData
    let provider: CGDataProvider! = CGDataProvider(data: cfdata)
    if provider == nil {
        print("CGDataProvider is not supposed to be nil")
        return nil
    }
    let cgimage: CGImage! = CGImage(
        width: width,
        height: height,
        bitsPerComponent: 8,
        bitsPerPixel: 32,
        bytesPerRow: width * pixelDataSize,
        space: CGColorSpaceCreateDeviceRGB(),
        bitmapInfo: CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedFirst.rawValue),
        provider: provider,
        decode: nil,
        shouldInterpolate: true,
        intent: .defaultIntent
    )
    if cgimage == nil {
        print("CGImage is not supposed to be nil")
        return nil
    }
    return UIImage(cgImage: cgimage)
}