2D游戏引擎（九）——添加背景支持

2d游戏中，基本背景类型为以下4种:
1.纯色背景

2.图像背景

3.动画背景

4.滚动背景

在下面的Background类中，支持前3种背景(其中第3种背景为自定义的:星空背景)，第4种背景将在以后展开。

程序清单:

//-----------------------------------------------------------------

// Background Object

// C++ Header - Background.h

//-----------------------------------------------------------------

#pragma once

//-----------------------------------------------------------------

// Include Files

//-----------------------------------------------------------------

#include <windows.h>

#include "Bitmap.h"

//-----------------------------------------------------------------

// Background Class

//-----------------------------------------------------------------

class Background

{

protected:

// Member Variables

int m_iWidth, m_iHeight;

COLORREF m_crColor;

Bitmap* m_pBitmap;

public:

// Constructor(s)/Destructor

Background(int iWidth, int iHeight, COLORREF crColor);

Background(Bitmap* pBitmap);

virtual ~Background();

// General Methods

virtual void Update();

virtual void Draw(HDC hDC);

// Accessor Methods

int GetWidth() { return m_iWidth; };

int GetHeight() { return m_iHeight; };

};

//-----------------------------------------------------------------

// Starry Background Class

//-----------------------------------------------------------------

class StarryBackground : Background

{

protected:

// Member Variables

int m_iNumStars; //星星数量

int m_iTwinkleDelay; //星星闪烁延迟

POINT m_ptStars[100]; //位置

COLORREF m_crStarColors[100]; //颜色

public:

// Constructor(s)/Destructor

StarryBackground(int iWidth, int iHeight, int iNumStars = 100,

int iTwinkleDelay = 50);

virtual ~StarryBackground();

// General Methods

virtual void Update();

virtual void Draw(HDC hDC);

};

//-----------------------------------------------------------------

// Background Object

// C++ Source - Background.cpp

//-----------------------------------------------------------------

//-----------------------------------------------------------------

// Include Files

//-----------------------------------------------------------------

#include "Background.h"

//-----------------------------------------------------------------

// Background Constructor(s)/Destructor

//-----------------------------------------------------------------

Background::Background(int iWidth, int iHeight, COLORREF crColor)

{

// Initialize the member variables

m_iWidth = iWidth;

m_iHeight = iHeight;

m_crColor = crColor;

m_pBitmap = NULL;

}

Background::Background(Bitmap* pBitmap)

{

// Initialize the member variables

m_crColor = 0;

m_pBitmap = pBitmap;

m_iWidth = pBitmap->GetWidth();

m_iHeight = pBitmap->GetHeight();

}

Background::~Background()

{

}

//-----------------------------------------------------------------

// Background General Methods

//-----------------------------------------------------------------

void Background::Update()

{

// Do nothing since the basic background is not animated

}

void Background::Draw(HDC hDC)

{

// Draw the background

if (m_pBitmap != NULL)

m_pBitmap->Draw(hDC, 0, 0);

else

{

RECT rect = { 0, 0, m_iWidth, m_iHeight };

HBRUSH hBrush = CreateSolidBrush(m_crColor);

FillRect(hDC, &rect, hBrush);

DeleteObject(hBrush);

}

}

//-----------------------------------------------------------------

// StarryBackground Constructor

//-----------------------------------------------------------------

StarryBackground::StarryBackground(int iWidth, int iHeight, int iNumStars,

int iTwinkleDelay) : Background(iWidth, iHeight, 0)

{

// Initialize the member variables

m_iNumStars = min(iNumStars, 100);

m_iTwinkleDelay = iTwinkleDelay;

// Create the stars

for (int i = 0; i < iNumStars; i++)

{

m_ptStars[i].x = rand() % iWidth;

m_ptStars[i].y = rand() % iHeight;

m_crStarColors[i] = RGB(128, 128, 128);

}

}

StarryBackground::~StarryBackground()

{

}

//-----------------------------------------------------------------

// StarryBackground General Methods

//-----------------------------------------------------------------

void StarryBackground::Update()

{

// Randomly change the shade of the stars so that they twinkle

int iRGB;

for (int i = 0; i < m_iNumStars; i++)

if ((rand() % m_iTwinkleDelay) == 0)

{

iRGB = rand() % 256;

m_crStarColors[i] = RGB(iRGB, iRGB, iRGB);

}

}

void StarryBackground::Draw(HDC hDC)

{

// Draw the solid black background

RECT rect = { 0, 0, m_iWidth, m_iHeight };

HBRUSH hBrush = CreateSolidBrush(RGB(0, 0, 0));

FillRect(hDC, &rect, hBrush);

DeleteObject(hBrush);

// Draw the stars

for (int i = 0; i < m_iNumStars; i++)

SetPixel(hDC, m_ptStars[i].x, m_ptStars[i].y, m_crStarColors[i]);

}