C++模拟OpenGL库——图形光栅化理论及实现（一)：项目设置、画布和画点等基本操作

目录

 

创建画布类以及画点操作、画布清洗

Render函数，画出屏幕雪花效果

⭐当前整体源码

---

创建Windows桌面应用程序

设置相关全局变量

// 全局变量:
HINSTANCE hInst;                                // 当前实例
WCHAR szTitle[MAX_LOADSTRING];                  // 标题栏文本
WCHAR szWindowClass[MAX_LOADSTRING];            // 主窗口类名

HWND    hWnd;
int     wWidth = 800;
int     wHeight = 600;
HDC     hDC;
HDC     hMem;

设置位图参数及绘制Render函数

    /*===========创建绘图用的位图========*/
    void* buffer = 0;

    hDC = GetDC(hWnd);
    hMem = ::CreateCompatibleDC(hDC);

    BITMAPINFO  bmpInfo;
    bmpInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    bmpInfo.bmiHeader.biWidth = wWidth;
    bmpInfo.bmiHeader.biHeight = wHeight;
    bmpInfo.bmiHeader.biPlanes = 1;
    bmpInfo.bmiHeader.biBitCount = 32;
    bmpInfo.bmiHeader.biCompression = BI_RGB; 
    bmpInfo.bmiHeader.biSizeImage = 0;
    bmpInfo.bmiHeader.biXPelsPerMeter = 0;
    bmpInfo.bmiHeader.biYPelsPerMeter = 0;
    bmpInfo.bmiHeader.biClrUsed = 0;
    bmpInfo.bmiHeader.biClrImportant = 0;

    HBITMAP hBmp = CreateDIBSection(hDC, &bmpInfo, DIB_RGB_COLORS, (void**)&buffer, 0, 0);//在这里创建buffer的内存
    SelectObject(hMem, hBmp);

    memset(buffer, 0, wWidth * wHeight * 4); //创建buffer内存

创建画布类以及画点操作、画布清洗

#pragma once
//#include "GTMATH.hpp"
#include 
typedef unsigned char	byte;
namespace GT{
	//像素结构体
	struct RGBA
	{
		byte m_b;
		byte m_g;
		byte m_r;
		byte m_a;

		RGBA(byte _r = 255,
			byte _g = 255,
			byte _b = 255,
			byte _a = 255)
		{
			m_r = _r;
			m_g = _g;
			m_b = _b;
			m_a = _a;
		}
	};

	//画布类，封装一些之后的图形API
	class Canvas {
	private:
		int m_width;
		int m_height;
		RGBA* m_buffer;

	public:
		Canvas(int _width, int _height, void* _buffer) {
			if (_width <= 0 || _height <= 0) {
				m_width = -1;
				m_height = -1;
				m_buffer = nullptr;
			}
			m_width = _width;
			m_height = _height;
			m_buffer = (RGBA*)_buffer;
		}
		~Canvas()
		{
		}

		//=========画布清洗============
		void clear() {
			if (m_buffer != nullptr) {
				memset(m_buffer, 0, sizeof(RGBA) * m_width * m_height);
			}
		}

		//=========画点操作============
		void drawPoint(int x, int y, RGBA _color) {
			if (x < 0 || x >= m_width || y < 0 || y >= m_height) {
				return;
			}
			m_buffer[y * m_width + x] = _color;
		}
	};
}

Render函数，画出屏幕雪花效果

void Render() {
    _canvas->clear();

    //逐像素绘制
    for (int i = 0; i < wWidth; i++) {
        for (int j = 0; j < wHeight; j++) {
            GT::RGBA _color(rand() % 255, rand() % 255, rand() % 255);
            _canvas->drawPoint(i, j, _color);
        }
    }

    //在这里画到设备上，hMem相当于缓冲区
    BitBlt(hDC, 0, 0, wWidth, wHeight, hMem, 0, 0, SRCCOPY);
}

效果如下：

⭐当前整体源码

之后的基础均在此基础代码上进行

C++_OpengL.cpp

// C++_OpenGL.cpp : 定义应用程序的入口点。
//

#include "framework.h"
#include "C++_OpenGL.h"
#include "Canvas.h"

#define MAX_LOADSTRING 100

// 全局变量:
HINSTANCE hInst;                                // 当前实例
WCHAR szTitle[MAX_LOADSTRING];                  // 标题栏文本
WCHAR szWindowClass[MAX_LOADSTRING];            // 主窗口类名

HWND    hWnd;
int     wWidth = 800;
int     wHeight = 600;
HDC     hDC;
HDC     hMem;

GT::Canvas* _canvas = nullptr;

// 此代码模块中包含的函数的前向声明:
ATOM                MyRegisterClass(HINSTANCE hInstance);//向系统注册窗体类型
BOOL                InitInstance(HINSTANCE, int);
LRESULT CALLBACK    WndProc(HWND, UINT, WPARAM, LPARAM);
INT_PTR CALLBACK    About(HWND, UINT, WPARAM, LPARAM);

void Render() {
    _canvas->clear();

    //逐像素绘制
    for (int i = 0; i < wWidth; i++) {
        for (int j = 0; j < wHeight; j++) {
            GT::RGBA _color(rand() % 255, rand() % 255, rand() % 255);
            _canvas->drawPoint(i, j, _color);
        }
    }

    //在这里画到设备上，hMem相当于缓冲区
    BitBlt(hDC, 0, 0, wWidth, wHeight, hMem, 0, 0, SRCCOPY);
}

int APIENTRY wWinMain(_In_ HINSTANCE hInstance,
                     _In_opt_ HINSTANCE hPrevInstance,
                     _In_ LPWSTR    lpCmdLine,
                     _In_ int       nCmdShow)
{
    UNREFERENCED_PARAMETER(hPrevInstance);
    UNREFERENCED_PARAMETER(lpCmdLine);

    // TODO: 在此处放置代码。

    // 初始化全局字符串
    LoadStringW(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING);
    LoadStringW(hInstance, IDC_COPENGL, szWindowClass, MAX_LOADSTRING);
    MyRegisterClass(hInstance);

    // 执行应用程序初始化:
    if (!InitInstance (hInstance, nCmdShow))
    {
        return FALSE;
    }

    HACCEL hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_COPENGL));

    /*===========创建绘图用的位图========*/
    void* buffer = 0;

    hDC = GetDC(hWnd);
    hMem = ::CreateCompatibleDC(hDC);

    BITMAPINFO  bmpInfo;
    bmpInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    bmpInfo.bmiHeader.biWidth = wWidth;
    bmpInfo.bmiHeader.biHeight = wHeight;
    bmpInfo.bmiHeader.biPlanes = 1;
    bmpInfo.bmiHeader.biBitCount = 32;
    bmpInfo.bmiHeader.biCompression = BI_RGB; 
    bmpInfo.bmiHeader.biSizeImage = 0;
    bmpInfo.bmiHeader.biXPelsPerMeter = 0;
    bmpInfo.bmiHeader.biYPelsPerMeter = 0;
    bmpInfo.bmiHeader.biClrUsed = 0;
    bmpInfo.bmiHeader.biClrImportant = 0;

    HBITMAP hBmp = CreateDIBSection(hDC, &bmpInfo, DIB_RGB_COLORS, (void**)&buffer, 0, 0);//在这里创建buffer的内存
    SelectObject(hMem, hBmp);

    memset(buffer, 0, wWidth * wHeight * 4); //创建buffer内存

    //================创建绘图用的位图==========
    _canvas = new GT::Canvas(wWidth, wHeight, buffer);


    MSG msg;

    // 主消息循环:
    while (GetMessage(&msg, nullptr, 0, 0))
    {
        if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg))
        {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
        Render();
    }

    return (int) msg.wParam;
}



//
//  函数: MyRegisterClass()
//
//  目标: 注册窗口类。
//
ATOM MyRegisterClass(HINSTANCE hInstance)
{
    WNDCLASSEXW wcex;

    wcex.cbSize = sizeof(WNDCLASSEX);

    wcex.style          = CS_HREDRAW | CS_VREDRAW;
    wcex.lpfnWndProc    = WndProc;
    wcex.cbClsExtra     = 0;
    wcex.cbWndExtra     = 0;
    wcex.hInstance      = hInstance;
    wcex.hIcon          = LoadIcon(hInstance, MAKEINTRESOURCE(IDI_COPENGL));
    wcex.hCursor        = LoadCursor(nullptr, IDC_ARROW);
    wcex.hbrBackground  = (HBRUSH)(COLOR_WINDOW+1);
    wcex.lpszMenuName   = NULL;
    wcex.lpszClassName  = szWindowClass;
    wcex.hIconSm        = LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_SMALL));

    return RegisterClassExW(&wcex);
}

//
//   函数: InitInstance(HINSTANCE, int)
//
//   目标: 保存实例句柄并创建主窗口
//
//   注释:
//
//        在此函数中，我们在全局变量中保存实例句柄并
//        创建和显示主程序窗口。
//
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
   hInst = hInstance; // 将实例句柄存储在全局变量中

   hWnd = CreateWindowW(szWindowClass, szTitle, WS_POPUP,
      CW_USEDEFAULT, 0, wWidth, wHeight, nullptr, nullptr, hInstance, nullptr);

   if (!hWnd)
   {
      return FALSE;
   }

   ShowWindow(hWnd, nCmdShow);
   UpdateWindow(hWnd);

   return TRUE;
}

//
//  函数: WndProc(HWND, UINT, WPARAM, LPARAM)
//
//  目标: 处理主窗口的消息。
//
//  WM_COMMAND  - 处理应用程序菜单
//  WM_PAINT    - 绘制主窗口
//  WM_DESTROY  - 发送退出消息并返回
//
//
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_COMMAND:
        {
            int wmId = LOWORD(wParam);
            // 分析菜单选择:
            switch (wmId)
            {
            case IDM_ABOUT:
                DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About);
                break;
            case IDM_EXIT:
                DestroyWindow(hWnd);
                break;
            default:
                return DefWindowProc(hWnd, message, wParam, lParam);
            }
        }
        break;
    case WM_PAINT:
        {
            PAINTSTRUCT ps;
            HDC hdc = BeginPaint(hWnd, &ps);
            // TODO: 在此处添加使用 hdc 的任何绘图代码...
            EndPaint(hWnd, &ps);
        }
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hWnd, message, wParam, lParam);
    }
    return 0;
}

// “关于”框的消息处理程序。
INT_PTR CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{
    UNREFERENCED_PARAMETER(lParam);
    switch (message)
    {
    case WM_INITDIALOG:
        return (INT_PTR)TRUE;

    case WM_COMMAND:
        if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL)
        {
            EndDialog(hDlg, LOWORD(wParam));
            return (INT_PTR)TRUE;
        }
        break;
    }
    return (INT_PTR)FALSE;
}

Canvas.h

#pragma once
//#include "GTMATH.hpp"
#include 
typedef unsigned char	byte;
namespace GT{
	//像素结构体
	struct RGBA
	{
		byte m_b;
		byte m_g;
		byte m_r;
		byte m_a;

		RGBA(byte _r = 255,
			byte _g = 255,
			byte _b = 255,
			byte _a = 255)
		{
			m_r = _r;
			m_g = _g;
			m_b = _b;
			m_a = _a;
		}
	};

	//画布类，封装一些之后的图形API
	class Canvas {
	private:
		int m_width;
		int m_height;
		RGBA* m_buffer;

	public:
		Canvas(int _width, int _height, void* _buffer) {
			if (_width <= 0 || _height <= 0) {
				m_width = -1;
				m_height = -1;
				m_buffer = nullptr;
			}
			m_width = _width;
			m_height = _height;
			m_buffer = (RGBA*)_buffer;
		}
		~Canvas()
		{
		}

		//=========画布清洗============
		void clear() {
			if (m_buffer != nullptr) {
				memset(m_buffer, 0, sizeof(RGBA) * m_width * m_height);
			}
		}

		//=========画点操作============
		void drawPoint(int x, int y, RGBA _color) {
			if (x < 0 || x >= m_width || y < 0 || y >= m_height) {
				return;
			}
			m_buffer[y * m_width + x] = _color;
		}
	};
}