在 Swift 中创建随机像素图像

Question

我想在 swift 中创建一个随机像素生成器。

我怎样才能在 swift 中创建类似以下代码的内容？

演示随机像素图像创建的Java程序

import java.io.File; 
import java.io.IOException; 
import java.awt.image.BufferedImage; 
import javax.imageio.ImageIO; 
public class RandomImage 
{ 
    public static void main(String args[])throws IOException 
    { 
        // Image file dimensions 
        int width = 640, height = 320; 

        // Create buffered image object 
        BufferedImage img = null; 
        img = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB); 

        // file object 
        File f = null; 

        // create random values pixel by pixel 
        for (int y = 0; y < height; y++) 
        { 
            for (int x = 0; x < width; x++) 
            { 
                int a = (int)(Math.random()*256); //generating 
                int r = (int)(Math.random()*256); //values 
                int g = (int)(Math.random()*256); //less than 
                int b = (int)(Math.random()*256); //256 

                int p = (a<<24) | (r<<16) | (g<<8) | b; //pixel 

                img.setRGB(x, y, p); 
            } 
        } 

        // write image 
        try
        { 
            f = new File("G:\\Out.jpg"); 
            ImageIO.write(img, "jpg", f); 
        } 
        catch(IOException e) 
        { 
            System.out.println("Error: " + e); 
        } 
    } 
} 

这是我只能实现的。从下面的代码中，你就会知道我绝对是一个快速的新手。

import Cocoa

class ViewController: NSViewController {

                let height=500
                let width=500
                for y in 0..<height {
                    for x in 0..<width {

                    }
                }



    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    }

    override var representedObject: Any? {
        didSet {
        }
    }
}

Answer 1

你可以使用下面的函数来创建随机的 UIImage

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

    func createRandomUIImage(width: Int, height: Int) -> UIImage? {
        var pixels = [PixelData]()
        let rgbColorSpace = CGColorSpaceCreateDeviceRGB()
        let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedFirst.rawValue)
        let bitsPerComponent = 8
        let bitsPerPixel = 32

        for _ in 0..<width {
            for _ in 0..<height {
                pixels.append(PixelData(a: .random(in: 0...255), r: .random(in: 0...255), g: .random(in: 0...255), b: .random(in: 0...255)))
            }
        }

        guard let providerRef = CGDataProvider(data: NSData(bytes: &pixels,
                                length: pixels.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)
    }

Answer 2

这是一个针对 macOS 的解决方案（基于 this iOS solution），它创建了一个 NSImage：

public struct Pixel {
    var a,r,g,b: UInt8
}

extension NSImage {
    convenience init?(pixels: [Pixel], 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<Pixel>.size) as CFData)
            else { return nil }
        guard let cgim = CGImage(
            width: width,
            height: height,
            bitsPerComponent: 8,
            bitsPerPixel: 32,
            bytesPerRow: width * MemoryLayout<Pixel>.size,
            space: CGColorSpaceCreateDeviceRGB(),
            bitmapInfo: CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedFirst.rawValue),
            provider: providerRef,
            decode: nil,
            shouldInterpolate: true,
            intent: .defaultIntent)
        else { return nil }
        self.init(cgImage: cgim, size: NSSize(width: width, height: height))
    }
}

要使用此初始化程序，请创建一个 Pixel 数组，然后调用 NSImage，传入 pixels、width 和 height。它返回一个可选的NSImage，即nil，如果在创建图像时出现任何问题。

示例用法：

let height = 500
let width = 500

var pixels: [Pixel] = .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 = NSImage(pixels: pixels, width: width, height: height)

感谢@LeoDabus 建议将该函数作为NSImage 的便捷初始化器。