1.首先在準備一張圖片

2.測試壓縮效果

3.測試解壓縮效果

將桌面a.jpg刪除



4.源代碼

package com.zsh.algorithm.tree;import java.io.*; import java.util.*;/*** @author:Ronin* @since:2021/9/29* @email:1817937322@qq.com*/public class HuffmanEncrypt {public static void main(String[] args) { // String str = "i love china china china oh"; // byte[] bytes = huffmanZip(str.getBytes()); // System.out.println(Arrays.toString(bytes)); // String s = calHuffmanZipRatio(str.getBytes(), bytes); // System.out.println("壓縮率為:" + s); // String s1 = byteToBinaryString(false, (byte) -1); // System.out.println("測試-1的補碼為:"+ s1); // decode(huffmanCodesMap, bytes); // System.out.println("以下是文件壓縮的測試----------------");// fileEncode("C:\\Users\\18179\\Desktop\\a.jpg", "C:\\Users\\18179\\Desktop\\a.zip");fileDecode("C:\\Users\\18179\\Desktop\\a.zip", "C:\\Users\\18179\\Desktop\\a.jpg");}//用來存儲轉換二進制字符串集合private static StringBuilder stringBuilder = new StringBuilder();//哈夫曼編碼表private static Map<Byte, String> huffmanCodesMap = new HashMap<>();//---------------------------------------以下是壓縮相關函數------------------------------------------///*** 赫夫曼編碼封裝方法** @param bytes* @return*/public static byte[] huffmanZip(byte[] bytes) {//1.計算字符串中每個字符出現的次數，并字符、次數封裝到EncryptNode結點中，將其加入到list集合中List<EncryptNode> encryptNodeList = calByteNums(bytes);//outputList(encryptNodeList);//2.構建哈夫曼樹EncryptNode root = buildHuffmanTree(encryptNodeList);// preErgodic(root);//3.生成赫夫曼編碼表Map<Byte, String> huffmanCodes = getHuffmanCodes(root);//System.out.println(huffmanCodes);//4.轉換為赫夫曼編碼字節表return zip(bytes, huffmanCodes);}/*** 計算字符串中的每個字符的長度** @param bytes 待計算的字符串* @return 返回list集合*/public static List<EncryptNode> calByteNums(byte[] bytes) {Map<Byte, Integer> map = new HashMap<>();byte[] charArray = bytes;for (byte c : charArray) {if (map.containsKey(c)) {int num = map.get(c);map.replace(c, num, num + 1);} else {map.put(c, 1);}}List<EncryptNode> list = new ArrayList<>();for (Map.Entry<Byte, Integer> entry : map.entrySet()) {Byte key = entry.getKey();Integer value = entry.getValue();list.add(new EncryptNode(key, value));}return list;}/*** 構建赫夫曼樹** @param list 權重集合* @return 返回root節點*/public static EncryptNode buildHuffmanTree(List<EncryptNode> list) {while (list.size() > 1) {Collections.sort(list);EncryptNode leftNode = list.remove(0);EncryptNode rightNode = list.remove(0);EncryptNode parentNode = new EncryptNode(null, leftNode.value + rightNode.value);parentNode.left = leftNode;parentNode.right = rightNode;list.add(parentNode);}return list.remove(0);}/*** 重載getHuffmanCodes(EncryptNode node, String path, StringBuilder stringBuilder)** @param root 根節點* @return 哈夫曼編碼map集合*/public static Map<Byte, String> getHuffmanCodes(EncryptNode root) {if (root == null) {return null;} else {getHuffmanCodes(root.left, "0", stringBuilder);getHuffmanCodes(root.right, "1", stringBuilder);}return huffmanCodesMap;}/*** 赫夫曼編碼** @param node 結點* @param path 1代表右結點，0代表左結點路徑* @param stringBuilder 用于path拼接*/public static void getHuffmanCodes(EncryptNode node, String path, StringBuilder stringBuilder) {StringBuilder stringBuilder2 = new StringBuilder(stringBuilder);stringBuilder2.append(path);if (node != null) {if (node.c == null) {getHuffmanCodes(node.left, "0", stringBuilder2);getHuffmanCodes(node.right, "1", stringBuilder2);} else {huffmanCodesMap.put(node.c, stringBuilder2.toString());}}}/*** @param bytes 待編碼字節數組* @param entry 赫夫曼編碼集合* @return 返回編碼后的byte數組*/public static byte[] zip(byte[] bytes, Map<Byte, String> entry) {StringBuilder stringBuilder = new StringBuilder();for (byte ch : bytes) {stringBuilder.append(entry.get(ch));}//System.out.println("stringBuilder=" + stringBuilder.toString());int length = stringBuilder.length();int len = (length + 7) / 8;byte[] huffmanCodeBytes = new byte[len];int index = 0;for (int k = 0; k < length; k += 8) {String str;if ((k + 8) > length) {str = stringBuilder.substring(k);} else {str = stringBuilder.substring(k, k + 8);}huffmanCodeBytes[index] = (byte) Integer.parseInt(str, 2);index++;}return huffmanCodeBytes;}/*** 計算赫夫曼壓縮率** @param original 未壓縮前的字節數組* @param newByte 壓縮后的字節數組* @return 壓縮率*/public static String calHuffmanZipRatio(byte[] original, byte[] newByte) {double zipRatio = (double) (original.length - newByte.length) / original.length * 100;String s = String.format("%.2f", zipRatio);return s + "%";}//---------------------------------以上是壓縮相關函數--------------------------------------------------------////---------------------------------以下是解壓縮相關函數-----------------------------------------------------//private static byte[] decode(Map<Byte, String> huffmanCodesMap, byte[] bytes) {StringBuilder stringBuilder = new StringBuilder();for (int k = 0; k < bytes.length; k++) {boolean flag = (k == bytes.length - 1);stringBuilder.append(byteToBinaryString(!flag, bytes[k]));}Map<String, Byte> reverseMap = new HashMap<>();for (Map.Entry<Byte, String> map : huffmanCodesMap.entrySet()) {reverseMap.put(map.getValue(), map.getKey());}List<Byte> list = new ArrayList<>();for (int i = 0; i < stringBuilder.length(); ) {int count = 1;Byte b = null;boolean flag = true;while (flag) {String key = stringBuilder.substring(i, i + count);b = reverseMap.get(key);if (b == null) {count++;} else {flag = false;}}list.add(b);i += count;}byte[] result = new byte[list.size()];for (int k = 0; k < result.length; k++) {result[k] = list.get(k);}return result;}/*** @param flag 如果為true, 表示需要進行高位補齊；如果是false，表示不需要進行高位補齊-->因為最后一位不一定剛好是滿足八位* @param be 這是將轉換為二進制字符串的字節* @return 返回二進制字符串*/private static String byteToBinaryString(boolean flag, byte be) {int beInt = be;if (flag) {beInt |= 256; //按位與 , 解決正數的高位補齊的問題}String s = Integer.toBinaryString(beInt); //補碼，正數需要高位補齊，負數需要截取if (flag) {return s.substring(s.length() - 8);} else {return s;}}//---------------------------------以上是解壓縮相關函數-----------------------------------------------------////---------------------------------以下是文件壓縮解壓相關函數-----------------------------------------------------///*** 文件壓縮方法 --- 赫夫曼編碼壓縮* @param readFile 壓縮文件路徑 文件 + 文件名* @param storeFile 壓縮之后存儲的路徑 文件 + 文件名*/private static void fileEncode(String readFile, String storeFile) {FileInputStream is = null;ObjectOutputStream oos = null;FileOutputStream os = null;try {is = new FileInputStream(readFile);byte[] bytes = new byte[is.available()];is.read(bytes);byte[] huffmanBytes = huffmanZip(bytes);os = new FileOutputStream(storeFile);oos = new ObjectOutputStream(os);oos.writeObject(huffmanBytes);oos.writeObject(huffmanCodesMap);os.write(huffmanBytes);} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} finally {try {oos.close();os.close();is.close();} catch (IOException e) {e.printStackTrace();}}}public static void fileDecode(String zipFile, String dstFile) {System.out.println("文件解壓開始----------------------");FileInputStream is = null;ObjectInputStream ois = null;FileOutputStream os = null;try {is = new FileInputStream(zipFile);ois = new ObjectInputStream(is);byte[] huffmanBytes = (byte[])ois.readObject();Map<Byte, String> huffmanCodes = (Map<Byte, String>) ois.readObject();byte[] bytes = decode(huffmanCodes, huffmanBytes);os = new FileOutputStream(dstFile);os.write(bytes);} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} catch (ClassNotFoundException e) {e.printStackTrace();} finally {try {os.close();ois.close();is.close();} catch (IOException e) {e.printStackTrace();}}}//---------------------------------以上是文件壓縮解壓相關函數-----------------------------------------------------////先序遍歷赫夫曼樹public static void preErgodic(EncryptNode cur) {if (cur == null) {return;}System.out.println(cur);preErgodic(cur.left);preErgodic(cur.right);}//打印list集合public static <T> void outputList(List<T> list) {for (T t : list) {System.out.println(t);}} }/*** 實現Comparable接口，便于使用Collections.sort排序*/ class EncryptNode implements Comparable<EncryptNode> {public int value; //出現的次數public Byte c; //字符public EncryptNode left;public EncryptNode right;public EncryptNode(int value) {this.value = value;}public EncryptNode(Byte c, int value) {this.value = value;this.c = c;}@Overridepublic int compareTo(EncryptNode o) {return this.value - o.value; //升序}@Overridepublic String toString() {return "EncryptNode{" +"value=" + value +", c=" + c +'}';} }

結束~

總結

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