bmp_image_compression_bmp图像压缩算法_

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <windows.h> #define lmax 256 //压缩时每一段包含的最大像素数 #define header 11 //每一段需要11位来保存这一段的信息（8位用来表示段长度 //，3位用来表示每一像素占的位数） int bmpWidth; //图像的宽 int bmpHeight; //图像的高 RGBQUAD *pColorTable; //颜色表指针 int biBitCount; //图像类型，每像素位数 unsigned char *pBmpBuf; //灰度值数组 int lineByte; //每一行的字节数 BITMAPFILEHEADER h; //头部 BITMAPINFOHEADER head; //头部信息 int i, j; // 循环要用到的遍历变量 int *s, *l, *b; //这三个数组的意义和书上是一样的 int m; //分割的段数 int le(int i) //log(i+1)向上取整 { int k = 1; i = i / 2; while (i > 0) { k++; i = i / 2; } return k; } void traceback(int n, int s[], int l[]) //和书上一样不解释了 { if (n == 0) return; traceback(n - l[n], s, l); s[m++] = n - l[n]; } void compress(unsigned char p[], int s[], int l[], int b[])//这个也和书上一样 { int n = bmpWidth * bmpHeight; int bmax; s[0] = 0; for (i = 1; i <= n; i++) { b[i] = le(p[i]); bmax = b[i]; s[i] = s[i - 1] + bmax; l[i] = 1; for (j = 2; j <= i && j <= lmax; j++) { if (bmax < b[i - j + 1]) bmax = b[i - j + 1]; if (s[i] > s[i - j] + j * bmax) { s[i] = s[i - j] + j * bmax; l[i] = j; } } s[i] += header; } } void collect(unsigned char p[], int s[], int l[], int b[]) { int max; int n = bmpWidth * bmpHeight; traceback(n, s, l); s[m] = n; for (j = 1; j <= m; j++) { l[j] = l[s[j]]; max = -1; for (i = s[j - 1] + 1; i <= s[j]; i++) { //特别注意这个地方，书上错了 if (le(p[i]) > max) //b[i]应该取第i段中占用位数最大的那个 max = le(p[i]); } b[j] = max; } } void store(unsigned char *a, int *j, int *left, int bit, int temp)//将temp存到数组里 { if (*left <=bit) { a[(*j)++] += temp >> (bit - (*left)); a[(*j)] +=(temp << (8 + (*left) - bit)) & 0xff; *left = 8 - (bit - (*left)); }else { a[(*j)] += (temp << (*left - bit)) & 0xff; *left -= bit; } } void compressToFile(char*file,unsigned char p[], int l[], int b[], int m) //压缩存到文件里 { FILE *out = fopen(file, "wb"); int n = bmpWidth * bmpHeight, left, k = 1, t; unsigned char *a = (unsigned char*) malloc(n); memset(a, 0, n); left = 8; j = 0; for (i = 1; i <= m; i++) { store(a,&j,&left,8,l[i] - 1); store(a,&j,&left,3,b[i] - 1); t = k + l[i]; for (; k < t; k++) { store(a,&j,&left,b[i],p[k]); } } head.biSizeImage = j + 1; //修改文件大小，这个解压图像中要用到 fwrite(&h, sizeof(BITMAPFILEHEADER), 1, out); fwrite(&head, sizeof(BITMAPINFOHEADER), 1, out); fwrite(pColorTable, sizeof(RGBQUAD), 256, out); fwrite(a, 1, j + 1, out); fclose(out); } unsigned char* readBmp(char *file) //读取文件 { unsigned char*pBmpBuf; FILE *fp = fopen(file, "rb"); fread(&h, sizeof(BITMAPFILEHEADER), 1, fp); //获取图片头信息 fread(&head, sizeof(BITMAPINFOHEADER), 1, fp); //定义位图信息头结构变量，读取位图信息头进内存，存放在变量head中 bmpWidth = head.biWidth; //获取图像宽、高、每像素所占位数等信息 bmpHeight = head.biHeight; biBitCount = head.biBitCount; lineByte = (bmpWidth * biBitCount / 8 + 3) / 4 * 4;//定义变量，计算图像每行像素所占的字节数（必须是4的倍数） if (biBitCount == 8) { pColorTable = (RGBQUAD*) malloc(sizeof(RGBQUAD) * 256);//申请颜色表所需要的空间，读颜色表进内存 fread(pColorTable, sizeof(RGBQUAD), 256, fp); //灰度图像有颜色表，且颜色表表项为256 } pBmpBuf = (unsigned char*) malloc(sizeof(unsigned char) * (lineByte //申请位图数据所需要的空间，读位图数据进内存 * bmpHeight + 1)); fread(pBmpBuf + 1, 1, lineByte * bmpHeight, fp); //位图数组下标从1开始 fclose(fp); //关闭文件 return pBmpBuf; } int main() { char *file = "input.bmp";//原始图像 pBmpBuf = readBmp(file); s = (int*) malloc(sizeof(int) * (bmpWidth * bmpHeight + 1)); l = (int*) malloc(sizeof(int) * (bmpWidth * bmpHeight + 1)); b = (int*) malloc(sizeof(int) * (bmpWidth * bmpHeight + 1)); compress(pBmpBuf, s, l, b); collect(pBmpBuf, s, l, b); compressToFile("sqh.bmp",pBmpBuf, l, b, m); return 0; }