swift 判斷/比較兩張圖片是否相同 - 感知哈希算法

首先是對圖片進行處理:

//1.縮小圖片尺寸
    func scaleToSize(img: UIImage, size: CGSize) -> UIImage {
        UIGraphicsBeginImageContext(size)
        img.draw(in: CGRect(x: 0, y: 0, width: size.width, height: size.height))
        let scaledImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return scaledImage!
    }

//2.簡化色彩 將圖片轉換成灰度圖片
    func getGrayImage(sourceImage: UIImage) -> UIImage {
        let imageRef: CGImage = sourceImage.cgImage!
        let width: Int = imageRef.width
        let height: Int = imageRef.height

        let colorSpace = CGColorSpaceCreateDeviceGray()
        let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.none.rawValue)
        let context: CGContext = CGContext(data: nil, width: width, height: height, bitsPerComponent: 8, bytesPerRow: 0, space: colorSpace, bitmapInfo: bitmapInfo.rawValue)!

        let rect: CGRect = CGRect.init(x: 0, y: 0, width: width, height: height)
        context.draw(imageRef, in: rect)

        let outPutImage: CGImage = context.makeImage()!

        let newImage: UIImage = UIImage.init(cgImage: outPutImage)

        return newImage
    }

//3. 計算平均值, 比較像素的灰度
    func pHashValueWithImage(image: UIImage) -> NSString {
        let pHashString = NSMutableString()
        let imageRef = image.cgImage!
        let width = imageRef.width
        let height = imageRef.height
        let pixelData = imageRef.dataProvider!.data
        let data: UnsafePointer<UInt8> = CFDataGetBytePtr(pixelData)
        var sum: Int = 0
        for i in 0..<width * height {
            if data[i] != 0 {
                sum = sum + Int(data[i])
            }
        }
        let avr = sum / (width * height)
        for i in 0..<width * height {
            if Int(data[i]) >= avr {
                pHashString.append("1")
            } else {
                pHashString.append("0")
            }
        }
        return pHashString
    }

//4.計算哈希值 如果不相同的數據位不超過5，就說明兩張圖片很相似；如果大於10，就說明這是兩張不同的圖片。
    func getDifferentValueCountWithString(str1: NSString, str2: NSString) -> NSInteger {
        var diff: NSInteger = 0
        let s1 = str1.utf8String!
        let s2 = str2.utf8String!
        for i in 0..<str1.length {
            if s1[i] != s2[i] {
                diff += 1
            }
        }
        return diff
    }

寫個共用方法來比較兩個圖片是否相同

    /// 比較兩個圖片是否相同, 這裏比較尺寸爲20*20
    ///
    /// - Parameters:
    ///   - imageOne: 圖片1
    ///   - imageTwo: 圖片2
    /// - Returns: 是否相同的布爾值
    func isEqualImage(imageOne: UIImage, imageTwo: UIImage) -> Bool {
        var equalResult = false
        let mImageOne = self.getGrayImage(sourceImage: self.scaleToSize(img: imageOne, size: CGSize(width: 20, height: 20)))
        let mImageTwo = self.getGrayImage(sourceImage: self.scaleToSize(img: imageTwo, size: CGSize(width: 20, height: 20)))
        let diff = self.getDifferentValueCountWithString(str1: self.pHashValueWithImage(image: mImageOne), str2: self.pHashValueWithImage(image: mImageTwo))
        print(diff)
        if diff > 10 {
            equalResult = false
        } else {
            equalResult = true
        }
        return equalResult
    }

通過調用上面的共用方法,傳入兩個待比較的UIImage對象, 得到返回的Bool, 根據該布爾值進行相應的操作