SDL基础使用03（渲染显示bmp图片）

基于渲染器 显示bmp图片

• 1. 初始化SDL SDL_Init
• 1. 创建窗口 SDL_CreateWindow
• 1. 基于窗口创建渲染器 SDL_CreateRenderer
• 1. 加载bmp图片到surface SDL_LoadBMP
• 1. 根据图片surface创建纹理 SDL_CreateTextureFromSurface
• 1. 绘制三部曲

  清空渲染器上一次显示 SDL_RenderClear
  拷贝纹理数据到渲染器 SDL_RenderCopy
  更新渲染器显示 SDL_RenderPresent

• 1. 释放资源，退出 SDL_FreeSurface......

#include <iostream>
/* 纹理和渲染(渲染显示bmp图片) */
extern "C"
{
#include <SDL.h>
}

#pragma comment(lib, "SDL2.lib")


#undef main
int main()
{
    // 1. 初始化
    int nRet = SDL_Init(SDL_INIT_EVERYTHING);
    if (nRet < 0)
    {
        std::cout << "SDL Error: " << SDL_GetError() << std::endl;
        return -1;
    }

    // 2. 创建窗口
    SDL_Window* pWnd = SDL_CreateWindow("Title",
        SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
        640, 480,
        SDL_WINDOW_SHOWN);
    if (NULL == pWnd)
    {
        std::cout << "SDL Error: " << SDL_GetError() << std::endl;
        return -1;
    }

    // 3. 创建渲染        SDL_RENDERER_ACCELERATED   GPU硬件加速渲染
    SDL_Renderer* pRenderer = SDL_CreateRenderer(pWnd, -1, SDL_RENDERER_ACCELERATED); 
    if (NULL == pRenderer)
    {
        SDL_DestroyWindow(pWnd);
        std::cout << "SDL Error: " << SDL_GetError() << std::endl;
        return -1;
    }

    // 4. 加载bmp图片到surface
    SDL_Surface* pSurface = SDL_LoadBMP("./Panda.bmp");        // 加载bmp图片
    if (NULL == pSurface)
    {
        SDL_DestroyRenderer(pRenderer);
        SDL_DestroyWindow(pWnd);
        std::cout << "SDL Error: " << SDL_GetError() << std::endl;
        return -1;
    }

    SDL_Rect rect = { 0, 0, pSurface->w - 50, pSurface->h + 50 };
    // 5. 根据Surface创建纹理
    SDL_Texture*  pTexture = SDL_CreateTextureFromSurface(pRenderer, pSurface);
    if (NULL == pTexture)
    {
        SDL_FreeSurface(pSurface);
        SDL_DestroyRenderer(pRenderer);
        SDL_DestroyWindow(pWnd);
        std::cout << "SDL Error: " << SDL_GetError() << std::endl;
        return -1;
    }

    // 6. 绘制三部曲
    SDL_RenderClear(pRenderer);                                // 清空一下渲染器（防止有残留的数据）                            
    SDL_RenderCopy(pRenderer, pTexture, &rect, &rect);        // 将纹理数据拷贝到渲染器缓冲区中
    SDL_RenderPresent(pRenderer);                            // 刷新渲染器显示

    SDL_Delay(2000);

    // 7. 释放资源，退出
    // 释放表面
    if (pSurface)
    {
        SDL_FreeSurface(pSurface);
    }
    // 释放纹理
    if (pTexture)
    {
        SDL_DestroyTexture(pTexture);
    }
    // 释放渲染
    if (pRenderer)
    {
        SDL_DestroyRenderer(pRenderer);
    }
    // 释放窗口
    if (pWnd)
    {
        SDL_DestroyWindow(pWnd);
    }
    SDL_Quit();

    return 0;
}