哈夫曼编码—文件的压缩与解压（Java）
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压缩代码
package cn.guizimo.huffmancode;
import java.io.*;
import java.util.*;
/**
* @author guizimo
* @date 2020/8/8 11:55 上午
*/
public class HuffmanCode {
public static void main(String[] args) {
String zipFile = "d://123.png";
String dstFile = "d://123.zip";
zipFile(zipFile, dstFile);;
System.out.println("压缩成功!");
}
public static void unZipFile(String zipFile, String dstFile) {
InputStream is = null;
ObjectInputStream ois = null;
OutputStream 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 = huffmanUnzip(huffmanCodes, huffmanBytes);
os = new FileOutputStream(dstFile);
os.write(bytes);
} catch (Exception e) {
System.out.println(e.getMessage());
} finally {
try {
os.close();
ois.close();
is.close();
} catch (Exception e2) {
System.out.println(e2.getMessage());
}
}
}
public static void zipFile(String srcFile, String dstFile) {
OutputStream os = null;
ObjectOutputStream oos = null;
FileInputStream is = null;
try {
is = new FileInputStream(srcFile);
byte[] b = new byte[is.available()];
is.read(b);
byte[] huffmanBytes = huffmanZip(b);
os = new FileOutputStream(dstFile);
oos = new ObjectOutputStream(os);
oos.writeObject(huffmanBytes);
oos.writeObject(huffmanCodes);
} catch (Exception e) {
System.out.println(e.getMessage());
} finally {
try {
is.close();
oos.close();
os.close();
} catch (Exception e) {
System.out.println(e.getMessage());
}
}
}
//哈夫曼解压
private static byte[] huffmanUnzip(Map<Byte, String> huffmanCodes, byte[] huffmanBytes) {
StringBuilder stringBuilder = new StringBuilder();
for (int i = 0; i < huffmanBytes.length; i++) {
byte b = huffmanBytes[i];
boolean flag = (i == huffmanBytes.length - 1);
stringBuilder.append(byteToBitString(!flag, b));
}
//解码,反向编码表
HashMap<String, Byte> map = new HashMap<>();
for (Map.Entry<Byte, String> entry : huffmanCodes.entrySet()) {
map.put(entry.getValue(), entry.getKey());
}
//根据编码扫描到对应的ASCLL码对应的字符
List<Byte> list = new ArrayList<>();
for (int i = 0; i < stringBuilder.length(); ) {
int count = 1;
boolean flag = true;
Byte b = null;
while (flag) {
String key = stringBuilder.substring(i, i + count);
b = map.get(key);
if (b == null) {
count++;
} else {
flag = false;
}
}
list.add(b);
i += count;
}
byte b[] = new byte[list.size()];
for (int i = 0; i < b.length; i++) {
b[i] = list.get(i);
}
return b;
}
//转化二进制
private static String byteToBitString(boolean flag, byte b) {
int temp = b;
if (flag) {
temp |= 256;
}
String str = Integer.toBinaryString(temp);
if (flag) {
return str.substring(str.length() - 8);
} else {
return str;
}
}
//哈夫曼编码压缩
private static byte[] huffmanZip(byte[] bytes) {
List<Node> nodes = getNodes(bytes);
//哈夫曼树
Node huffmanTree = createHuffmanTree(nodes);
//哈夫曼编码表
Map<Byte, String> huffmanCodes = getCodes(huffmanTree);
//哈夫曼编码
byte[] zip = zip(bytes, huffmanCodes);
return zip;
}
//压缩
private static byte[] zip(byte[] bytes, Map<Byte, String> huffmanCodes) {
StringBuilder stringBuilder = new StringBuilder();
for (byte b : bytes) {
stringBuilder.append(huffmanCodes.get(b));
}
int len;
if (stringBuilder.length() % 8 == 0) {
len = stringBuilder.length() / 8;
} else {
len = stringBuilder.length() / 8 + 1;
}
byte[] by = new byte[len];
int index = 0;
for (int i = 0; i < stringBuilder.length(); i += 8) {
String strByte;
if (i + 8 > stringBuilder.length()) {
strByte = stringBuilder.substring(i);
by[index] = (byte) Integer.parseInt(strByte, 2);
index++;
} else {
strByte = stringBuilder.substring(i, i + 8);
by[index] = (byte) Integer.parseInt(strByte, 2);
index++;
}
}
return by;
}
static Map<Byte, String> huffmanCodes = new HashMap<Byte, String>();
static StringBuilder stringBuilder = new StringBuilder();
//重载
private static Map<Byte, String> getCodes(Node root) {
if (root == null) {
return null;
}
getCodes(root.left, "0", stringBuilder);
getCodes(root.right, "1", stringBuilder);
return huffmanCodes;
}
//获取哈夫曼编码
private static void getCodes(Node node, String code, StringBuilder stringBuilder) {
StringBuilder builder = new StringBuilder(stringBuilder);
builder.append(code);
if (node != null) {
if (node.data == null) { //递归
getCodes(node.left, "0", builder);
getCodes(node.right, "1", builder);
} else {
huffmanCodes.put(node.data, builder.toString());
}
}
}
//前序遍历
private static void preOrder(Node root) {
if (root != null) {
root.preOrder();
} else {
System.out.println("哈夫曼树为空");
}
}
//生成哈夫曼树
private static Node createHuffmanTree(List<Node> nodes) {
while (nodes.size() > 1) {
Collections.sort(nodes);
Node leftNode = nodes.get(0);
Node rightNode = nodes.get(1);
Node parent = new Node(null, leftNode.weight + rightNode.weight);
parent.left = leftNode;
parent.right = rightNode;
nodes.remove(leftNode);
nodes.remove(rightNode);
nodes.add(parent);
}
return nodes.get(0);
}
//接收字节数组
private static List<Node> getNodes(byte[] bytes) {
List<Node> nodes = new ArrayList<>();
Map<Byte, Integer> counts = new HashMap<>();
for (byte b : bytes) {
Integer count = counts.get(b);
if (count == null) {
counts.put(b, 1);
} else {
counts.put(b, count + 1);
}
}
//遍历map
for (Map.Entry<Byte, Integer> entry : counts.entrySet()) {
nodes.add(new Node(entry.getKey(), entry.getValue()));
}
return nodes;
}
}
class Node implements Comparable<Node> {
Byte data;
int weight; //字符出现的次数
Node left;
Node right;
//前序遍历
public void preOrder() {
System.out.println(this);
if (this.left != null) {
this.left.preOrder();
}
if (this.right != null) {
this.right.preOrder();
}
}
public Node(Byte data, int weight) {
this.data = data;
this.weight = weight;
}
@Override
public int compareTo(Node o) {
//从小到大排序
return this.weight - o.weight;
}
@Override
public String toString() {
return "Node{" +
"data=" + data +
", weight=" + weight +
'}';
}
}
解压代码
package cn.guizimo.huffmancode;
import java.io.*;
import java.util.*;
/**
* @author guizimo
* @date 2020/8/8 11:55 上午
*/
public class HuffmanCode {
public static void main(String[] args) {
String zipFile = "d://Uninstall.zip";
String dstFile = "d://Uninstall2.xml";
unZipFile(zipFile, dstFile);
System.out.println("解压成功!");
}
public static void unZipFile(String zipFile, String dstFile) {
InputStream is = null;
ObjectInputStream ois = null;
OutputStream 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 = huffmanUnzip(huffmanCodes, huffmanBytes);
os = new FileOutputStream(dstFile);
os.write(bytes);
} catch (Exception e) {
System.out.println(e.getMessage());
} finally {
try {
os.close();
ois.close();
is.close();
} catch (Exception e2) {
System.out.println(e2.getMessage());
}
}
}
public static void zipFile(String srcFile, String dstFile) {
OutputStream os = null;
ObjectOutputStream oos = null;
FileInputStream is = null;
try {
is = new FileInputStream(srcFile);
byte[] b = new byte[is.available()];
is.read(b);
byte[] huffmanBytes = huffmanZip(b);
os = new FileOutputStream(dstFile);
oos = new ObjectOutputStream(os);
oos.writeObject(huffmanBytes);
oos.writeObject(huffmanCodes);
} catch (Exception e) {
System.out.println(e.getMessage());
} finally {
try {
is.close();
oos.close();
os.close();
} catch (Exception e) {
System.out.println(e.getMessage());
}
}
}
//哈夫曼解压
private static byte[] huffmanUnzip(Map<Byte, String> huffmanCodes, byte[] huffmanBytes) {
StringBuilder stringBuilder = new StringBuilder();
for (int i = 0; i < huffmanBytes.length; i++) {
byte b = huffmanBytes[i];
boolean flag = (i == huffmanBytes.length - 1);
stringBuilder.append(byteToBitString(!flag, b));
}
//解码,反向编码表
HashMap<String, Byte> map = new HashMap<>();
for (Map.Entry<Byte, String> entry : huffmanCodes.entrySet()) {
map.put(entry.getValue(), entry.getKey());
}
//根据编码扫描到对应的ASCLL码对应的字符
List<Byte> list = new ArrayList<>();
for (int i = 0; i < stringBuilder.length(); ) {
int count = 1;
boolean flag = true;
Byte b = null;
while (flag) {
String key = stringBuilder.substring(i, i + count);
b = map.get(key);
if (b == null) {
count++;
} else {
flag = false;
}
}
list.add(b);
i += count;
}
byte b[] = new byte[list.size()];
for (int i = 0; i < b.length; i++) {
b[i] = list.get(i);
}
return b;
}
//转化二进制
private static String byteToBitString(boolean flag, byte b) {
int temp = b;
if (flag) {
temp |= 256;
}
String str = Integer.toBinaryString(temp);
if (flag) {
return str.substring(str.length() - 8);
} else {
return str;
}
}
//哈夫曼编码压缩
private static byte[] huffmanZip(byte[] bytes) {
List<Node> nodes = getNodes(bytes);
//哈夫曼树
Node huffmanTree = createHuffmanTree(nodes);
//哈夫曼编码表
Map<Byte, String> huffmanCodes = getCodes(huffmanTree);
//哈夫曼编码
byte[] zip = zip(bytes, huffmanCodes);
return zip;
}
//压缩
private static byte[] zip(byte[] bytes, Map<Byte, String> huffmanCodes) {
StringBuilder stringBuilder = new StringBuilder();
for (byte b : bytes) {
stringBuilder.append(huffmanCodes.get(b));
}
int len;
if (stringBuilder.length() % 8 == 0) {
len = stringBuilder.length() / 8;
} else {
len = stringBuilder.length() / 8 + 1;
}
byte[] by = new byte[len];
int index = 0;
for (int i = 0; i < stringBuilder.length(); i += 8) {
String strByte;
if (i + 8 > stringBuilder.length()) {
strByte = stringBuilder.substring(i);
by[index] = (byte) Integer.parseInt(strByte, 2);
index++;
} else {
strByte = stringBuilder.substring(i, i + 8);
by[index] = (byte) Integer.parseInt(strByte, 2);
index++;
}
}
return by;
}
static Map<Byte, String> huffmanCodes = new HashMap<Byte, String>();
static StringBuilder stringBuilder = new StringBuilder();
//重载
private static Map<Byte, String> getCodes(Node root) {
if (root == null) {
return null;
}
getCodes(root.left, "0", stringBuilder);
getCodes(root.right, "1", stringBuilder);
return huffmanCodes;
}
//获取哈夫曼编码
private static void getCodes(Node node, String code, StringBuilder stringBuilder) {
StringBuilder builder = new StringBuilder(stringBuilder);
builder.append(code);
if (node != null) {
if (node.data == null) { //递归
getCodes(node.left, "0", builder);
getCodes(node.right, "1", builder);
} else {
huffmanCodes.put(node.data, builder.toString());
}
}
}
//前序遍历
private static void preOrder(Node root) {
if (root != null) {
root.preOrder();
} else {
System.out.println("哈夫曼树为空");
}
}
//生成哈夫曼树
private static Node createHuffmanTree(List<Node> nodes) {
while (nodes.size() > 1) {
Collections.sort(nodes);
Node leftNode = nodes.get(0);
Node rightNode = nodes.get(1);
Node parent = new Node(null, leftNode.weight + rightNode.weight);
parent.left = leftNode;
parent.right = rightNode;
nodes.remove(leftNode);
nodes.remove(rightNode);
nodes.add(parent);
}
return nodes.get(0);
}
//接收字节数组
private static List<Node> getNodes(byte[] bytes) {
List<Node> nodes = new ArrayList<>();
Map<Byte, Integer> counts = new HashMap<>();
for (byte b : bytes) {
Integer count = counts.get(b);
if (count == null) {
counts.put(b, 1);
} else {
counts.put(b, count + 1);
}
}
//遍历map
for (Map.Entry<Byte, Integer> entry : counts.entrySet()) {
nodes.add(new Node(entry.getKey(), entry.getValue()));
}
return nodes;
}
}
class Node implements Comparable<Node> {
Byte data;
int weight; //字符出现的次数
Node left;
Node right;
//前序遍历
public void preOrder() {
System.out.println(this);
if (this.left != null) {
this.left.preOrder();
}
if (this.right != null) {
this.right.preOrder();
}
}
public Node(Byte data, int weight) {
this.data = data;
this.weight = weight;
}
@Override
public int compareTo(Node o) {
//从小到大排序
return this.weight - o.weight;
}
@Override
public String toString() {
return "Node{" +
"data=" + data +
", weight=" + weight +
'}';
}
}
感谢
尚硅谷
以及勤劳的自己
来源：oschina
链接：https://my.oschina.net/guizimo/blog/4479349