用c语言写一个基于游程编码算法的图片压缩

好的，以下是基于游程编码算法的图片压缩的C语言代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_RLEN 255

// 定义游程编码结构体
struct rle {
    int len;
    int val;
};

// 读取图片像素矩阵
void readPixels(unsigned char *pixels, int width, int height, FILE *f)
{
    int count = 0;
    while (count < width * height) {
        int c = fgetc(f);
        if (c == EOF) {
            break;
        }
        pixels[count++] = (unsigned char)c;
    }
}

// 游程编码
int rle_encode(unsigned char *in, int len, struct rle **out)
{   
    *out = malloc(sizeof(struct rle) * len);
    if (*out == NULL) {
        return -1;
    }

    int count = 0, k = 0;
    for (int i = 0; i < len; i++) {
        (*out)[k].val = in[i];
        count = 1;
        while (i < len - 1 && in[i] == in[i+1] && count < MAX_RLEN) {
            count++;
            i++;
        }
        (*out)[k].len = count;
        k++;
    }

    return k;
}

// 游程解码
void rle_decode(struct rle *in, int len, unsigned char *out)
{
    int count = 0;
    for (int i = 0; i < len; i++) {
        for (int j = 0; j < in[i].len; j++) {
            out[count++] = (unsigned char)in[i].val;
        }
    }
}

// 压缩图片
void compressImage(unsigned char *pixels, int width, int height, char *filename)
{
    FILE *f = fopen(filename, "wb");
    if (f == NULL) {
        printf("Error: could not open file for writing\n");
        return;
    }

    struct rle *rle_pixels;
    int rle_len = rle_encode(pixels, width * height, &rle_pixels);

    fwrite(&width, sizeof(int), 1, f);
    fwrite(&height, sizeof(int), 1, f);
    fwrite(rle_pixels, sizeof(struct rle), rle_len, f);

    fclose(f);
}

// 解压图片
void decompressImage(char *filename, unsigned char **pixels, int *width, int *height)
{
    FILE *f = fopen(filename, "rb");
    if (f == NULL) {
        printf("Error: could not open file for reading\n");
        return;
    }

    fread(width, sizeof(int), 1, f);
    fread(height, sizeof(int), 1, f);
    struct rle *rle_pixels = malloc(sizeof(struct rle) * (*width) * (*height));
    fread(rle_pixels, sizeof(struct rle), (*width) * (*height), f);

    *pixels = malloc((*width) * (*height));
    rle_decode(rle_pixels, (*width) * (*height), *pixels);

    free(rle_pixels);
    fclose(f);
}

int main()
{
    // 读取图片像素矩阵
    FILE *f = fopen("input.pgm", "rb");
    if (f == NULL) {
        printf("Error: could not open file for reading\n");
        return -1;
    }

    char format[3];
    fgets(format, 3, f);
    if (strcmp(format, "P5") != 0) {
        printf("Error: not a PGM file\n");
        return -1;
    }

    int width, height, maxval;
    fscanf(f, "%d %d %d", &width, &height, &maxval);
    if (maxval > 255) {
        printf("Error: cannot handle PGM files with maxval > 255\n");
        return -1;
    }

    unsigned char *pixels = malloc(width * height);
    readPixels(pixels, width, height, f);
    fclose(f);

    // 压缩图片
    compressImage(pixels, width, height, "output.rle");

    // 解压图片
    unsigned char *decompressed_pixels;
    int decompressed_width, decompressed_height;
    decompressImage("output.rle", &decompressed_pixels, &decompressed_width, &decompressed_height);

    // 检查解压是否正确
    if (decompressed_width != width || decompressed_height != height) {
        printf("Error: decompressed image has incorrect dimensions\n");
        return -1;
    }

    for (int i = 0; i < width * height; i++) {
        if (pixels[i] != decompressed_pixels[i]) {
            printf("Error: decompressed image is incorrect\n");
            return -1;
        }
    }

    printf("Compression and decompression successful\n");

    free(pixels);
    free(decompressed_pixels);

    return 0;
}

这段代码实现了对PGM格式图片的压缩和解压缩。其中，`rle_encode()`函数实现了游程编码算法，将像素矩阵压缩成了一个游程编码数组；`rle_decode()`函数实现了游程解码算法，将游程编码数组解码成了一个像素矩阵。`compressImage()`函数将像素矩阵压缩成了文件，`decompressImage()`函数将压缩文件解压成了像素矩阵。程序通过读取PGM格式图片来进行测试，也可以通过修改代码以适应其他图片格式。