iOS 隐形水印之 LSB 实现

class func baseEncode(data: UnsafeMutablePointer<UInt8>, infoData: Data, width w: Int, height h: Int) {    let kQHKeyData = kQFkey.data(using: .utf8)!    let kQHKeyDataCount = kQHKeyData.count    let kLenghtCount = kLengthBit        let markCount = kQHKeyDataCount + kLengthBitCount + kLenghtCount + infoData.count        var bStop = false    var markIndex = -1    var markIndexText: Int = 0    var markBin: QFLSBMarkBin?    var markLengthBitCount = 0        // 1、读取原数据    for y in 0..<h {        if bStop {            break;        }        for x in 0..<w {            let index = (y * w + x)                        let markIndexTemp = index / 8            if markIndexTemp >= markCount {                bStop = true                break            }
            // 2、水印信息的计算            if markIndex != markIndexTemp {                markIndex = markIndexTemp                                if markIndex < kQHKeyDataCount {                    markBin = .key                    markIndexText = Int(kQHKeyData[markIndex])                }                else if markIndex < kQHKeyDataCount + kLengthBitCount {                    markBin = .lengthBit                    markIndexText = kLengthBit                }                else if markIndex < kQHKeyDataCount + kLengthBitCount + kLenghtCount {                    markLengthBitCount += 1                    markBin = .length                    if markLengthBitCount == 1 {                        markIndexText = markCount%256                    }                    else if markLengthBitCount == 2 {                        markIndexText = Int(markCount>>8)                    }                    else {                        bStop = true                        break                    }                }                else if markIndex < markCount {                    markBin = .info                    markIndexText = Int(infoData[markIndex - (kQHKeyDataCount + kLengthBitCount + kLenghtCount)])                }            }                        if markBin == nil {                bStop = true                break            }                        // 3、读取原数据 & 获取最低有效位            let offset = 4 * index            let red = data[offset+1]            let redBinary = red % 2                        let markIndexTextBinaryIndex = index % 8            let markIndexTextBinary = Int((markIndexText / (1<<Int(markIndexTextBinaryIndex))) % 2)                        // 4、最低有效位记录            if redBinary != markIndexTextBinary {                if markIndexTextBinary == 0 {                    if red == 255 {                        data[offset+1] = 254                    }                    else {                        data[offset+1] = red + 1                    }                }                else {                    if red == 0 {                        data[offset+1] = 1                    }                    else {                        data[offset+1] = red - 1                    }                }            }        }    }}
// 逻辑上与 baseEncode 相同，读取原数据后记录到对应的水印数据信息上。class func baseDecode(data: UnsafeMutablePointer<UInt8>, width w: Int, height h: Int) -> (result: Bool, info: String) {
	// ......	    return (false, "解密");}

private func toPng() -> Bool
if !toPng() {	print("showScreenshot toPng 失败")	return}

let text = "QFScreenshot" as NSStringlet p = CGPoint(x: 20, y: 160)text.draw(at: p, withAttributes: [NSAttributedString.Key.font : UIFont.systemFont(ofSize: 16), NSAttributedString.Key.foregroundColor: UIColor(white: 0.5, alpha: 1)])