在 Swift 中将像素数组转换为 UIImage [英] Pixel Array to UIImage in Swift

问题描述

我一直在研究如何在 Swift 中将 rgb 像素数据数组转换为 UIImage.

I've been trying to figure out how to convert an array of rgb pixel data to a UIImage in Swift.

我将每个像素的 rgb 数据保存在一个简单的结构中:

I'm keeping the rgb data per pixel in a simple struct:

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

我已经使用了以下功能，但生成的图像不正确:

I've made my way to the following function, but the resulting image is incorrect:

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)!
}

关于如何将 rgb 数组正确转换为 UIImage 的任何提示或指示?

Any tips or pointers on how to properly convert an rgb array to an UIImage?

推荐答案

注意: 这是 iOS 创建 UIImage 的解决方案.有关 macOS 和 NSImage 的解决方案，请参阅此答案.

Note: This is a solution for iOS creating a UIImage. For a solution for macOS and NSImage, see this answer.

您唯一的问题是PixelData 结构中的数据类型必须是UInt8.我在 Playground 中创建了一个测试图像，内容如下:

Your only problem is that the data types in your PixelData structure need to be UInt8. I created a test image in a Playground with the following:

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)

<小时>

Swift 4 更新:

我更新了 imageFromARGB32Bitmap 以使用 Swift 4.该函数现在返回一个 UIImage? 并且 guard 用于返回 nil 如果出现任何问题.

I updated imageFromARGB32Bitmap to work with Swift 4. The function now returns a UIImage? and guard is used to return nil if anything goes wrong.

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)
}

<小时>

使其成为 UIImage 的便捷初始化器:

这个函数作为 UIImage 的 convenience 初始化器工作得很好.这是实现:

This function works well as a convenience initializer for UIImage. Here is the implementation:

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)
    }
}

以下是它的用法示例:

// 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)

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