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C++基于EasyX框架实现飞机大战小游戏

作者：Leleprogrammer

EasyX是针对C/C++的图形库，可以帮助使用C/C++语言的程序员快速上手图形和游戏编程。本文将利用EasyX框架实现飞机大战小游戏，需要的可以参考一下

正式使用Easyx之前，你需要先安装他！！

EasyX 2022 版 (2022-9-1 更新) - EasyX

选择合适的版本安装

安装结束后就可以开始敲代码啦！

这里作者使用的是Visual Studio 2022所以安装EasyX_20220901版本

启动Visual Studio 2022，新建一个空项目

这是工程目录：

首先来看看Bullet（子弹）类

头文件：

#pragma once
class Bullet
{
public:
    Bullet(int x, int y, int owner);
    int owner; // 0 means player, 1 means enemy
    int x;
    int y;
    int speed;
    int pic_w = 5;
    int pic_h = 11;
    bool dead = false;
    void move();
    void checkBound();
};

源文件：

#include "Bullet.h"
#include "constants.h"
 
Bullet::Bullet(int x, int y, int owner) {
    this->x = x;
    this->y = y;
    this->owner = owner;
    speed = 12;
}
 
void Bullet::move() {
    if (owner == 0) {
        y -= speed;
    }
    else {
        y += speed;
    }
}
 
void Bullet::checkBound() {
    if (owner == 0) {
        if (y + pic_h <= 0) {
            dead = true;
        }
    }
    else {
        if (y >= HEIGHT) {
            dead = true;
        }
    }
}

这里简单地实现了子弹的移动和检测超出边界，不难理解

Enemy类头文件：

#pragma once
class Enemy
{
public:
    Enemy(int type);
    int x;
    int y;
    int speed;
    int pic_w;
    int pic_h;
    int type;
    int health;
    int static_health;
    bool dead = false;
    void move();
    void checkBound();
};

源文件：

#include "Enemy.h"
#include "constants.h"
 
Enemy::Enemy(int type) {
    this->type = type;
    switch (type) {
    case 1:
        pic_w = 60;
        pic_h = 44;
        health = random(1, 2);
        break;
    case 2:
        pic_w = 70;
        pic_h = 100;
        health = random(3, 4);
        break;
    case 3:
        pic_w = 160;
        pic_h = 250;
        health = random(5, 6);
        break;
    default:
        pic_w = 60;
        pic_h = 44;
        health = 1;
        break;
    }
    x = random(0, WIDTH - pic_w);
    y = 0 - pic_h;
    speed = random(5,8);
    static_health = health;
}
 
void Enemy::move() {
    y += speed;
}
 
void Enemy::checkBound() {
    if (y >= HEIGHT || health <= 0) {
        dead = true;
    }
}

这里的类成员变量type表示敌机大小，3最大，同时血量最多，也实现了移动和检测超出边界功能

有的人会发现random方法以及WIDTH常量等，这里是因为我们将这些常量写在一个头文件下：

constants.h：

#pragma once
 
#ifndef WIDTH
#define WIDTH 800
#endif
 
#ifndef HEIGHT
#define HEIGHT 1000
#endif
 
#include <cstdlib>
#include <string>
 
using namespace std;
 
#ifndef random(a,x)
#define random(a,x) a+rand()%x
#endif
 
const string PATH = "./resources/";

接下来是Player.h

#pragma once
#include <string>
#include "constants.h"
using namespace std;
 
class Player
{
public:
    Player();
    int speed;
    int y;
    int x;
    int pic_w;
    int pic_h;
    void move(int a);
    void checkBound();
};

Player.cpp：

#include "Player.h"
#include "constants.h"
 
Player::Player() {
    speed = 12;
    y = HEIGHT - 170;
    x = 300;
    pic_w = 100;
    pic_h = 126;
}
 
void Player::move(int a) {
    if (a == 0) { // left
        x -= speed;
    }
    else { // right
        x += speed;
    }
}
 
void Player::checkBound() {
    if (x < 0) {
        x = 0;
    }
    else if (x + pic_w > WIDTH) {
        x = WIDTH - pic_w;
    }
}

代码都很短，也实现了移动和限制活动区域（checkBound）操作，不难理解

接下来是作者自己写了一个实用的头文件，用于判断2者是否碰撞，CheckCollide.h：

#pragma once
 
bool collide(
    int l,
    int r,
    int t,
    int d,
    int el,
    int er,
    int et,
    int ed) {
    if ((l <= er && t <= ed && l >= el && t >= et) ||
        (r >= el && t <= ed && r <= er && t >= et) ||
        (l <= er && d >= et && l >= el && d <= ed) ||
        (r >= el && d >= et && r <= er && d <= ed)) {
        return true;
    }
    return false;
}

其中，l、r、t、d分别为第一个物体的左边x坐标、右边x坐标、上边y坐标、下边y坐标，el、er、et、ed是第二个物体的，然后进行判断，返回bool值，这个待会在main.cpp会用到

接下来也是一个常用的头文件，因为easyx渲染透明图片很麻烦，所以这个方法通过计算来绘制，这个是借用了EasyX 绘制透明背景图这篇文章的代码，PhotoTransparent.h

#pragma once
 
#include <graphics.h>
#include "constants.h"
 
void drawAlpha(IMAGE* image, int x, int y, int width, int height, int pic_x = 0, int pic_y = 0, double AA = 1)
{
    // 变量初始化
    DWORD* dst = GetImageBuffer();            // GetImageBuffer() 函数，用于获取绘图设备的显存指针， EasyX 自带
    DWORD* draw = GetImageBuffer();
    DWORD* src = GetImageBuffer(image);        // 获取 picture 的显存指针
    int imageWidth = image->getwidth();        // 获取图片宽度
    int imageHeight = image->getheight();    // 获取图片宽度
    int dstX = 0;                            // 在 绘图区域 显存里像素的角标
    int srcX = 0;                            // 在 image 显存里像素的角标
 
    // 实现透明贴图 公式： Cp=αp*FP+(1-αp)*BP ， 贝叶斯定理来进行点颜色的概率计算
    for (int iy = 0; iy < height; iy++)
    {
        for (int ix = 0; ix < width; ix++)
        {
            // 防止越界
            if (ix + pic_x >= 0 && ix + pic_x < imageWidth && iy + pic_y >= 0 && iy + pic_y < imageHeight &&
                ix + x >= 0 && ix + x < WIDTH && iy + y >= 0 && iy + y < HEIGHT)
            {
                // 获取像素角标
                int srcX = (ix + pic_x) + (iy + pic_y) * imageWidth;
                dstX = (ix + x) + (iy + y) * WIDTH;
 
                int sa = ((src[srcX] & 0xff000000) >> 24) * AA;            // 0xAArrggbb; AA 是透明度
                int sr = ((src[srcX] & 0xff0000) >> 16);                // 获取 RGB 里的 R
                int sg = ((src[srcX] & 0xff00) >> 8);                    // G
                int sb = src[srcX] & 0xff;                                // B
 
                // 设置对应的绘图区域像素信息
                int dr = ((dst[dstX] & 0xff0000) >> 16);
                int dg = ((dst[dstX] & 0xff00) >> 8);
                int db = dst[dstX] & 0xff;
                draw[dstX] = ((sr * sa / 255 + dr * (255 - sa) / 255) << 16)  //公式： Cp=αp*FP+(1-αp)*BP  ； αp=sa/255 , FP=sr , BP=dr
                    | ((sg * sa / 255 + dg * (255 - sa) / 255) << 8)         //αp=sa/255 , FP=sg , BP=dg
                    | (sb * sa / 255 + db * (255 - sa) / 255);              //αp=sa/255 , FP=sb , BP=db
            }
        }
    }
}

接下来这一个是作者自己写的一个常用的头文件StringCharExchange.h：

#pragma once
 
#include <graphics.h>
#define BUFFERSIZE 1024
 
TCHAR* Transform(char c[BUFFERSIZE]) {
    TCHAR result[BUFFERSIZE];
    MultiByteToWideChar(CP_ACP, 0, c, -1, result, BUFFERSIZE);
    return result;
}
 
TCHAR* Transform(string s) {
    TCHAR result[BUFFERSIZE];
    char c[BUFFERSIZE];
    strcpy_s(c, s.c_str());
    MultiByteToWideChar(CP_ACP, 0, c, -1, result, BUFFERSIZE);
    return result;
}

上面实现了char*转TCHAR*以及string转TCHAR*

最后是main.cpp

#include <graphics.h>
#include "constants.h"
#include "Player.h"
#include "PhotoTransparent.h"
#include <time.h>
#include <vector>
#include "Bullet.h"
#include "Enemy.h"
#include "CheckCollide.h"
#include "StringCharExchange.h"
 
Player* player = new Player();
vector<Bullet>* bullets = new vector<Bullet>;
vector<Enemy>* enemies = new vector<Enemy>;
 
int startTime[5] = { 0 };
int durations[5] = { 200,1000,0,0,0 };
 
int health = 5;
int score = 0;
bool lose = false;
 
void DrawBackGroundImage() {
    IMAGE img;
    loadimage(&img, Transform(PATH+"background2.png"), WIDTH, HEIGHT);
    putimage(0, 0, &img);
}
 
void DrawPlayer() {
    IMAGE img;
    loadimage(&img, Transform(PATH + "myplane1.png"), player->pic_w, player->pic_h);
    drawAlpha(&img, player->x, player->y, player->pic_w, player->pic_h);
}
 
void DrawBullets() {
    for (int i = 0;i < bullets->size();i++) {
        Bullet* bullet = &(bullets->at(i));
        IMAGE img;
        loadimage(&img, Transform(PATH + "bullet1.png"));
        drawAlpha(&img, bullet->x, bullet->y, bullet->pic_w, bullet->pic_h);
    }
}
 
void DrawEnemies() {
    for (int i = 0;i < enemies->size();i++) {
        Enemy* enemy = &(enemies->at(i));
        IMAGE img;
        switch (enemy->type) {
        case 1:
            loadimage(&img, Transform(PATH + "small_enemy.png"));
            break;
        case 2:
            loadimage(&img, Transform(PATH + "mid_enemy.png"));
            break;
        case 3:
            loadimage(&img, Transform(PATH + "big_enemy.png"));
            break;
        default:
            break;
        }
        drawAlpha(&img, enemy->x, enemy->y, enemy->pic_w, enemy->pic_h);
    }
}
 
void UpdateBullets() {
    for (int i = 0;i < bullets->size();i++) {
        Bullet* bullet = &(bullets->at(i));
        bullet->move();
        bullet->checkBound();
        if (bullet->dead) {
            swap(bullets->at(i), bullets->at(bullets->size() - 1));
            bullets->pop_back();
            i--;
        }
    }
}
 
void UpdateEnemies() {
    for (int i = 0;i < enemies->size();i++) {
        Enemy* enemy = &(enemies->at(i));
        enemy->move();
        enemy->checkBound();
        if (enemy->dead) {
            swap(enemies->at(i), enemies->at(enemies->size() - 1));
            enemies->pop_back();
            i--;
        }
    }
}
 
void CheckPlayerHit() {
    for (int i = 0;i < enemies->size();i++) {
        Enemy* enemy = &(enemies->at(i));
        int l, r, t, d;
        int el, er, et, ed;
        l = player->x;
        r = player->x + player->pic_w;
        t = player->y;
        d = player->y + player->pic_h;
        el = enemy->x;
        er = enemy->x + enemy->pic_w;
        et = enemy->y;
        ed = enemy->y + enemy->pic_h;
        if (collide(l, r, t, d, el, er, et, ed)) {
            health--;
            swap(enemies->at(i), enemies->at(enemies->size() - 1));
            enemies->pop_back();
            i--;
        }
    }
}
 
void CheckBulletHit() {
    for (int i = 0;i < bullets->size();i++) {
        Bullet* bullet = &(bullets->at(i));
        int l, r, t, d;
        l = bullet->x;
        r = bullet->x + bullet->pic_w;
        t = bullet->y;
        d = bullet->y + bullet->pic_h;
        for (int j = 0;j < enemies->size();j++) {
            Enemy* enemy = &(enemies->at(j));
            int el, er, et, ed;
            el = enemy->x;
            er = enemy->x + enemy->pic_w;
            et = enemy->y;
            ed = enemy->y + enemy->pic_h;
            if (collide(l, r, t, d, el, er, et, ed)) {
                enemy->health--;
                if (enemy->health <= 0 || enemy->dead) {
                    score += enemy->static_health;
                    swap(enemies->at(j), enemies->at(enemies->size() - 1));
                    enemies->pop_back();
                }
                j--;
                swap(bullets->at(i), bullets->at(bullets->size() - 1));
                bullets->pop_back();
                i--;
                break;
            }
        }
    }
}
 
void _DrawText() {
    settextcolor(RGB(0, 0, 255));
    settextstyle(26, 0, _T("simhei"));
    char c[BUFFERSIZE];
    snprintf(c, 64, "Health: %d", health);
    TCHAR* c2 = Transform(c);
    outtextxy(10, 10, c2);
    settextcolor(RGB(255, 0, 0));
    settextstyle(26, 0, _T("simhei"));
    char c3[BUFFERSIZE];
    snprintf(c3, 64, "Score: %d", score);
    TCHAR* c4 = Transform(c3);
    outtextxy(10, 44, c4);
}
 
void CheckLose() {
    if (health <= 0) {
        lose = true;
    }
}
 
void Draw() {
    CheckLose();
    DrawBackGroundImage();
    _DrawText();
    if (!lose) {
        UpdateBullets();
        UpdateEnemies();
        CheckPlayerHit();
        CheckBulletHit();
        DrawPlayer();
        DrawEnemies();
        DrawBullets();
    }
}
 
void Timer() {
    int endTime = clock();
    if (endTime - startTime[0] >= durations[0]) { // Create bullet event
        bullets->push_back(Bullet(player->x + player->pic_w / 2, player->y, 0));
        startTime[0] = endTime;
    }
    if (endTime - startTime[1] >= durations[1]) { // Create enemy event
        enemies->push_back(Enemy(random(1,3)));
        startTime[1] = endTime;
    }
}
 
int Listen() {
    if (GetAsyncKeyState(VK_ESCAPE)) {
        return 1;
    }
    if (GetAsyncKeyState(VK_LEFT)) {
        player->move(0);
        player->checkBound();
    }
    if (GetAsyncKeyState(VK_RIGHT)) {
        player->move(1);
        player->checkBound();
    }
    return 0;
}
 
int main() {
    initgraph(WIDTH, HEIGHT);
    setbkmode(TRANSPARENT);
    BeginBatchDraw();
    while (true) {
        Draw();
        if (Listen()) {
            break;
        }
        Timer();
        FlushBatchDraw();
    }
    EndBatchDraw();
    closegraph();
    return 0;
}

实现了程序的主流程

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