在C上读取二进制PGM

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

typedef struct {
    int width;
    int height;
    int maxVal;
    unsigned char* data;
} PGMImage;

PGMImage* readPGM(const char* filename) {
    FILE* file = fopen(filename, "rb");
    if (file == NULL) {
        printf("Failed to open file.\n");
        return NULL;
    }

    // 读取文件头
    char magicNum[3];
    fscanf(file, "%s", magicNum);
    if (magicNum[0] != 'P' || magicNum[1] != '5') {
        printf("Invalid PGM file.\n");
        fclose(file);
        return NULL;
    }

    int width, height, maxVal;
    fscanf(file, "%d %d %d", &width, &height, &maxVal);

    // 分配内存
    unsigned char* data = (unsigned char*)malloc(width * height * sizeof(unsigned char));
    if (data == NULL) {
        printf("Memory allocation failed.\n");
        fclose(file);
        return NULL;
    }

    // 读取图像数据
    fread(data, sizeof(unsigned char), width * height, file);

    // 关闭文件
    fclose(file);

    // 创建PGMImage结构体并返回
    PGMImage* image = (PGMImage*)malloc(sizeof(PGMImage));
    image->width = width;
    image->height = height;
    image->maxVal = maxVal;
    image->data = data;

    return image;
}

int main() {
    const char* filename = "image.pgm";
    PGMImage* image = readPGM(filename);
    if (image == NULL) {
        return 1;
    }

    // 使用读取到的图像数据进行后续处理

    // 释放内存
    free(image->data);
    free(image);

    return 0;
}