影像處理的實現與應用（Swift 版）

啊飒飒大苏打發表於2024-10-24
Swift

影像處理在現代技術中扮演著重要的角色，廣泛應用於計算機視覺、影像分析和機器學習等領域。本文將介紹一種簡單的影像處理方法，主要包括灰度轉換、去除邊框、提取有效區域和影像分割，並提供相應的 Swift 程式碼示例。

灰度轉換
灰度轉換是將彩色影像轉換為灰度影像的技術，目的是減少影像的複雜性。在 Swift 中，我們可以使用 Core Graphics 來實現灰度轉換：

swift

import UIKit

func convertToGray(image: UIImage) -> UIImage? {
let size = image.size
UIGraphicsBeginImageContext(size)

let context = UIGraphicsGetCurrentContext()
context?.translateBy(x: 0, y: size.height)
context?.scaleBy(x: 1.0, y: -1.0)

context?.setBlendMode(.copy)
context?.draw(image.cgImage!, in: CGRect(x: 0, y: 0, width: size.width, height: size.height))

context?.setBlendMode(.sourceIn)
context?.setFillColor(UIColor.gray.cgColor)
context?.fill(CGRect(x: 0, y: 0, width: size.width, height: size.height))

let grayImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()

return grayImage

}
去除影像邊框
去除影像的邊框可以透過遍歷影像的每一行和每一列來實現。以下是相應的程式碼：

swift

func clearBorders(image: UIImage, borderWidth: Int) -> UIImage? {
guard let cgImage = image.cgImage else { return nil }
let width = cgImage.width
let height = cgImage.height
let colorSpace = CGColorSpaceCreateDeviceRGB()

guard let context = CGContext(data: nil, width: width, height: height, bitsPerComponent: 8, bytesPerRow: 0, space: colorSpace, bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue) else { return nil }

context.draw(cgImage, in: CGRect(x: 0, y: 0, width: width, height: height))

let data = context.data?.assumingMemoryBound(to: UInt8.self)

for y in 0..<height {
    for x in 0..<width {
        if x < borderWidth || y < borderWidth || x >= width - borderWidth || y >= height - borderWidth {
            let pixelIndex = (y * width + x) * 4
            data?[pixelIndex] = 255     // Red
            data?[pixelIndex + 1] = 255 // Green
            data?[pixelIndex + 2] = 255 // Blue
        }
    }
}

let newCGImage = context.makeImage()
return newCGImage != nil ? UIImage(cgImage: newCGImage!) : nil

}
提取有效區域
有效區域提取是影像分析中的關鍵步驟。我們可以使用以下程式碼來提取有效區域：

swift

func extractValidRegion(image: UIImage, grayThreshold: UInt8) -> UIImage? {
guard let cgImage = image.cgImage else { return nil }
let width = cgImage.width
let height = cgImage.height
let colorSpace = CGColorSpaceCreateDeviceRGB()

guard let context = CGContext(data: nil, width: width, height: height, bitsPerComponent: 8, bytesPerRow: 0, space: colorSpace, bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue) else { return nil }

context.draw(cgImage, in: CGRect(x: 0, y: 0, width: width, height: height))

let data = context.data?.assumingMemoryBound(to: UInt8.self)

var minX = width, minY = height
var maxX = 0, maxY = 0

for y in 0..<height {
    for x in 0..<width {
        let pixelIndex = (y * width + x) * 4
        let grayValue = data?[pixelIndex] ?? 255
        
        if grayValue < grayThreshold {
            if minX > x { minX = x }
            if minY > y { minY = y }
            if maxX < x { maxX = x }
            if maxY < y { maxY = y }
        }
    }
}

let validRegion = context.makeImage()?.cropping(to: CGRect(x: minX, y: minY, width: maxX - minX + 1, height: maxY - minY + 1))
return validRegion != nil ? UIImage(cgImage: validRegion!) : nil

}更多內容聯絡1436423940
影像分割
影像分割可以將影像劃分為多個小塊。以下是實現這一功能的程式碼：

swift

func splitImage(image: UIImage, rows: Int, cols: Int) -> [UIImage] {
guard let cgImage = image.cgImage else { return [] }
let width = cgImage.width
let height = cgImage.height
var splitImages: [UIImage] = []

let pieceWidth = width / cols
let pieceHeight = height / rows

for i in 0..<rows {
    for j in 0..<cols {
        let rect = CGRect(x: j * pieceWidth, y: i * pieceHeight, width: pieceWidth, height: pieceHeight)
        if let pieceCGImage = cgImage.cropping(to: rect) {
            splitImages.append(UIImage(cgImage: pieceCGImage))
        }
    }
}

return splitImages

}
生成二進位制編碼
最後，將灰度影像轉換為二進位制字串：

swift

func generateBinaryCode(image: UIImage, grayThreshold: UInt8) -> String {
guard let cgImage = image.cgImage else { return "" }
let width = cgImage.width
let height = cgImage.height
let colorSpace = CGColorSpaceCreateDeviceRGB()

guard let context = CGContext(data: nil, width: width, height: height, bitsPerComponent: 8, bytesPerRow: 0, space: colorSpace, bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue) else { return "" }

context.draw(cgImage, in: CGRect(x: 0, y: 0, width: width, height: height))

let data = context.data?.assumingMemoryBound(to: UInt8.self)
var binaryCode = ""

for y in 0..<height {
    for x in 0..<width {
        let pixelIndex = (y * width + x) * 4
        let grayValue = data?[pixelIndex] ?? 255
        
        binaryCode.append(grayValue < grayThreshold ? "1" : "0")
    }
}
return binaryCode

}

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