3.1作业

原创已于 2024-03-04 10:14:36 修改 · 168 阅读

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#c语言

于 2024-03-01 20:12:02 首次发布

本文介绍了如何使用C语言中的fwrite和fread函数读取和修改BMP图片文件，将其转换为德国国旗，并通过getch函数实现密码输入时的星号隐藏功能。

使用fwrite、fread将一张随意的bmp图片，修改成德国的国旗

#include <stdio.h>
#include <stdint.h>

#define BMP_HEADER_SIZE 54
#define PIXEL_DATA_OFFSET 54

int main() {
    FILE *inputFile = fopen("input.bmp", "rb");
    FILE *outputFile = fopen("output.bmp", "wb");

    if (inputFile == NULL || outputFile == NULL) {
        printf("Error opening files.\n");
        return 1;
    }

    uint8_t header[BMP_HEADER_SIZE];
    fread(header, sizeof(uint8_t), BMP_HEADER_SIZE, inputFile);
    fwrite(header, sizeof(uint8_t), BMP_HEADER_SIZE, outputFile);

    fseek(inputFile, 0, SEEK_END);
    long fileSize = ftell(inputFile);
    fseek(inputFile, PIXEL_DATA_OFFSET, SEEK_SET);

    uint8_t pixelData[fileSize - PIXEL_DATA_OFFSET];
    fread(pixelData, sizeof(uint8_t), fileSize - PIXEL_DATA_OFFSET, inputFile);

for (int i = 0; i < (fileSize - PIXEL_DATA_OFFSET)/3; i += 3) {
         pixelData[i] = 0;     
        pixelData[i + 1] = 0; 
        pixelData[i + 2] = 0; 

}
for (int i = (fileSize -PIXEL_DATA_OFFSET)/3; i < (fileSize - PIXEL_DATA_OFFSET)/3*2; i += 3) {
        pixelData[i] = 0;     
        pixelData[i + 1] = 0; 
        pixelData[i + 2] = 255; 
	} 

for (int i = (fileSize-PIXEL_DATA_OFFSET)/3*2; i < (fileSize - PIXEL_DATA_OFFSET); i += 3) {
          pixelData[i] = 0;     
        pixelData[i + 1] = 255; 
        pixelData[i + 2] = 255; 
       
}

    fwrite(pixelData, sizeof(uint8_t), fileSize - PIXEL_DATA_OFFSET, outputFile);

    fclose(inputFile);
    fclose(outputFile);

    return 0;
}

使用提供的getch函数，编写一个专门用来输入密码的函数，要求输入密码的时候，显示 * 号，输入回车的时候，密码输入结束

#include <stdio.h>
#include <termios.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>

int getch() {
    int c = 0;
    struct termios org_opts, new_opts;
    int res = 0;
    res = tcgetattr(STDIN_FILENO, &org_opts);
    assert(res == 0);

    new_opts = org_opts;

    new_opts.c_lflag &= ~(ICANON | ECHO);
    tcsetattr(STDIN_FILENO, TCSANOW, &new_opts);

    c = getchar();

    res = tcsetattr(STDIN_FILENO, TCSANOW, &org_opts);
    assert(res == 0);
    return c;
}

char* getPassword() {
    char* password = (char*)malloc(100 * sizeof(char)); 
    if (!password) {
        printf("内存分配失败\n");
        exit(1);
    }

    int i = 0;
    char c;

    printf("请输入密码（按回车键结束）：");

    while (1) {
        c = getch();

        if (c == '\n') { 
            break;
        } else {
            password[i] = c; 
            printf("*"); 
            i++;
        }
    }

    printf("\n"); 
    return password;
}

int main() {
    char* password = getPassword();
    printf("您输入的密码是：%s\n", password);

    free(password); 

    return 0;
}