Huffman编码的多媒体应用

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武汉白云黄鹤站∶精华区
发信人: limey (石灰), 信区: Algorithm
标题: Huffman编码的多媒体应用
发信站: 武汉白云黄鹤站 (2001年12月30日20:32:06 星期天), 站内信件

    这是多媒体作业的一题：用Huffman编码压缩8*8的点阵图。
我自己写的，虽然多媒体已经考完了，但我仍然很高兴，呵呵。
把成果拿出来分享，也许下届师弟用得着。

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*                                                                  *
*HUFF.C Huffman encode for multimedia application 8*8 pixel Ver 3 *
*                                                                  *
*Ver 1: Complied in Borland Turbo C++ 3.0                         *
*Ver 2: Complied in Microsoft Visual C++ 6.0                      *
*Ver 3: Complied in Microsoft Visual C++ 6.0                      *
*          add code to print code table of the compression         *
*          print output message in Chinese                         *
*                                                                  *
*by Lee Meitz, Solid Mechanics, Huazhong Univ of Sci and Tech      *
*2001.11.15 - 2001.12.27                                           *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define DNUM 64    //define data number 8*8
#define LOOP 10000 //times of compression
typedef struct {
    unsigned short weight, data;
    unsigned short parent, lchild, rchild;
} HuffNode;
typedef struct {
    unsigned char code;
    unsigned short codelength;
} HuffCode;
unsigned int fCount[256] = {0};
unsigned int data_num;
unsigned int code_size;
unsigned int last_bit;
void FrequencyCount(unsigned char*);         //频率统计
void HuffSelect(HuffNode*, int, int*, int*); //从结点中选出权最小的两个节点
void HuffmanCodeTable(HuffNode*, HuffCode*); //构造huffman树，生成huffman编码
表
void HuffmanCompress(unsigned char*, unsigned char *, HuffCode*); //压缩数据

void BitPrint(unsigned char*);               //按位打印结果，用于调试
void main(void)
{
    int i, j, loop; //variable for loop
    HuffNode hfdata[2*DNUM] = {{0, 0, 0, 0, 0}}; //Huffman node
    HuffCode code_table[256] = {{0, 0}};     //code table will be searched
by subscript
    unsigned char hfcode[2*DNUM];            //output code
    time_t time1, time2;
/* unsigned char pixel[DNUM] = {
    1,2,3,4, 1,2,3,4, 1,2,3,4, 1,1,1,1};
*/
/* unsigned char pixel[DNUM] = {
        139,144,149,153,155,155,155,155,
        144,151,153,156,159,156,156,156,
        150,155,160,163,158,156,156,156,
        159,161,162,160,160,159,159,159,
        159,160,161,162,162,155,155,155,
        161,161,161,161,160,157,157,157,
        162,162,161,163,162,157,157,157,
        162,162,161,161,163,158,158,158};
*/
    unsigned char pixel[DNUM] = { //random data
        141, 101, 126, 111, 163, 112, 133, 156,
        103, 144, 111, 176, 117, 120, 188, 187,
        175, 164, 190, 156, 112, 179, 142, 119,
        140, 111, 127, 186, 196, 190, 189, 127,
        185, 103, 185, 110, 192, 139, 159, 104,
        151, 193, 178, 198, 114, 170, 179, 149,
        124, 149, 165, 108, 141, 176, 113, 164,
        101, 140, 120, 126, 173, 189, 158, 184};
/* unsigned char pixel[DNUM] = {
        202, 221, 159, 183, 41, 136, 247, 66,
        146, 29, 101, 108, 45, 61, 210, 236,
        90, 130, 54, 66, 132, 206, 119, 232,
        184, 135, 96, 78, 120, 41, 231, 203,
        150, 94, 172, 142, 122, 180, 150, 204,
        232, 121, 180, 221, 3, 207, 115, 147,
        72, 149, 169, 121, 76, 208, 235, 43,
        107, 58, 0, 237, 197, 7, 210, 89};
*/
    FrequencyCount(pixel);
    time1 = time(NULL);
    for (loop=0; loop<LOOP; loop++) {
        //set huffman nodes data and weight, i=0:255, j=1:64
        for (i=0, j=1, data_num=0; i<256; i++) {
            if (fCount[i]) {
                hfdata[j].weight = fCount[i];
                hfdata[j++].data = i;
                data_num ++;
            }
        }
        //build huffman tree and generate huffman code table
        HuffmanCodeTable(hfdata, code_table);
        //compress source data to huffman code using code table
        HuffmanCompress(pixel, hfcode, code_table);
        //initial hfdata and code_table
        for (j=0; j<2*DNUM; j++) {
            hfdata[j].data=0;
            hfdata[j].lchild=0;
            hfdata[j].parent=0;
            hfdata[j].rchild=0;
            hfdata[j].weight=0;
        }
    }
    time2 = time(NULL);
    //conclude
    printf("/n哈夫曼编码压缩图块，压缩报告/n华中科技大学力学系：李美之/n");
    printf("/n◎源数据（%d字节）:/n ", DNUM);
    for (i=0; i<DNUM; i++) {
        printf(i%8==7 ? "%02X/n " : "%02X ", pixel[i]);
    }
    printf("/n◎压缩数据（%d字节）:/n ", code_size);
    for (i=0; i<code_size; i++) {
        printf(i%8==7 ? "%02X/n " : "%02X ", hfcode[i]);
    }
    //打印码表
    printf("/n/n◎码表－编码字典（%d项）/n", data_num);
    for (i=0; i<256; i++) {
        if (code_table[i].codelength) {
            printf("%3d|%02X: ", i, i);
            for (j=0; j<code_table[i].codelength; j++) {
                printf("%d", ((code_table[i].code << j)&0x80)>>7);
            }
            printf("/t");
        }
    }
    printf("/n/n◎压缩率：%2.0f%% /t压缩时间：%.3f毫秒/n",
(float)code_size/DNUM * 100, 1E3*(time2-time1)/LOOP);
}
void BitPrint(unsigned char *hfcode)
{
    int i, j;
    int endbit = last_bit;
    unsigned char thebyte;
    for (i=0; i < code_size-1; i++) {
        thebyte = hfcode[i];
        for (j=0; j<8; j++) {
            printf("%d", ((thebyte<<j)&0x80)>>7);
        }
    }
    if (last_bit == 7) {
        endbit = -1;
    }
    thebyte = hfcode[i];
    for (j=7; j>endbit; j--) {
        printf("%d", ((thebyte<<(7-j))&0x80)>>7);
    }
}
void HuffmanCompress(unsigned char *pixel, unsigned char *hfcode, HuffCode *
code_table)
{
    int i, j;
    int curbit=7; //current bit in _thebyte_
    unsigned int bytenum=0; //number of destination code can also be
position of byte processed in destination
    unsigned int ptbyte=0; //position of byte processed in destination
    unsigned int curlength; //code's length of _curcode_
    unsigned char curcode; //current byte's huffman code
    unsigned char thebyte=0; //destination byte write
    unsigned char value; //current byte's value (pixel[])
    //process every byte
    for (i=0; i<DNUM; i++) {
        value = pixel[i];
        curcode = (code_table[value]).code;
        curlength = (code_table[value]).codelength;
        //move out every bit from curcode to destination
        for (j=0;j<=curlength;j++) {
            if ((curcode<<j)&0x80) {
                thebyte |= (unsigned char)(0x01<<curbit);
            }
            curbit --;
            if (curbit < 0) {
                hfcode[ptbyte++] = thebyte;
                thebyte = 0;
                curbit = 7;
                bytenum ++;
            }
        }
    }
    //think about which bit is the end
    if (curbit != 7) {
        hfcode[ptbyte] = thebyte;
        bytenum ++;
    }
    code_size = bytenum;
    last_bit = curbit;
}
void HuffmanCodeTable(HuffNode *hfdata, HuffCode *code_table)
{
    int i, j; //variable for loop
    int tree_num = 2*data_num - 1; //node of huffman tree
    int min1, min2; //two minimum weight
    int p; //the id of parent node
    unsigned char curcode; //current code being processing
    int curlength; //current code's length
    //build huffman tree
    for (i=data_num; i<tree_num; i++) {
        HuffSelect(hfdata, i, &min1, &min2);
        hfdata[min1].parent = i+1;
        hfdata[min2].parent = i+1;
        hfdata[i+1].lchild = min1;
        hfdata[i+1].rchild = min2;
        hfdata[i+1].weight = hfdata[min1].weight + hfdata[min2].weight;
    }
    //generate huffman code
    //i present the i th code, j present from leaf to root in huffman tree
    //hfdata[i].data (0:255) is a byte number
    //编码从叶读到根，按位从高往低压入一个字节，读编码从左向右
    for (i=1; i<=data_num; i++) {
        curcode = 0;
        curlength = 0;
        for (j=i, p=hfdata[j].parent; p!=0; j=p, p=hfdata[j].parent) {
            curlength ++;
            if (j==hfdata[p].lchild) curcode >>= 1;
            else curcode = (curcode >> 1) | 0x80; //0x80 = 128 = B1000 0000
        }
        code_table[hfdata[i].data].code = curcode;
        code_table[hfdata[i].data].codelength = curlength;
    }
}
void HuffSelect(HuffNode *hfdata, int end, int *min1, int *min2)
{
    int i; //variable for loop
    int s1, s2;
    HuffNode wath[30];
    for (i=0; i<30; i++) {
        wath[i] = hfdata[i];
    }
    s1 = s2 = 1;
    while (hfdata[s1].parent) {
        s1++;
    }
    for (i=2; i<=end; i++) {
        if (hfdata[i].parent == 0 && hfdata[i].weight < hfdata[s1].weight) {
            s1 = i;
        }
    }
    while (hfdata[s2].parent || s1 == s2) {
        s2++;
    }
    for (i=1; i<=end; i++) {
        if (hfdata[i].parent ==0 && hfdata[i].weight < hfdata[s2].weight &&
(i - s1)) {
            s2 = i;
        }
    }
    *min1 = s1;
    *min2 = s2;
}
void FrequencyCount(unsigned char *chs)
{
    int i;
    for (i=0; i<DNUM; i++) {
        fCount[*(chs+i)] ++;
    }
}

Limey
ilimey@263.net

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