SDL教程-001.创建窗体& 显示bmp图片

note1. hello,world

#include 
#include 

int main(int argc, char* argv[])
{
	if (SDL_Init(SDL_INIT_EVERYTHING) == -1)
		return(1);
	SDL_Delay(2000);
	SDL_Quit();

	return 0;
}

note2. sdl 展示一张bmp图片

#include 
#include 
int main(int argc, char* argv[])
{
	if (SDL_Init(SDL_INIT_VIDEO))
	{
		std::cout << "SDL_Init Error: " << SDL_GetError() << std::endl;
		return 1;
	}
	SDL_Window *win = SDL_CreateWindow("Hello World!", 100, 100, 640, 480, SDL_WINDOW_SHOWN);
	if (win == nullptr)
	{
		std::cout << "SDL_CreateWindow Error: " << SDL_GetError() << std::endl;
		return 1;
	}
	SDL_Renderer *ren = SDL_CreateRenderer(win, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
	if (ren == nullptr)
	{
		SDL_DestroyWindow(win);
		std::cout << "SDL_CreateRender Error: " << SDL_GetError() << std::endl;
		SDL_Quit();
		return 1;
	}
	std::string imagePath = "G:\\code\\AudioDemo\\Res\\bmps\\childrensday.bmp";
	SDL_Surface *bmp = SDL_LoadBMP(imagePath.c_str());
	if (bmp == nullptr)
	{
		SDL_DestroyRenderer(ren);
		SDL_DestroyWindow(win);
		std::cout << "SDL_LoadBMP Error: " << SDL_GetError() << std::endl;
		SDL_Quit();
		return 1;
	}
	SDL_Texture *tex = SDL_CreateTextureFromSurface(ren, bmp);
	SDL_FreeSurface(bmp);
	if (tex == nullptr)
	{
		SDL_DestroyRenderer(ren);
		SDL_DestroyWindow(win);
		std::cout << "SDL_CreateTextureFromSurface Error: " << SDL_GetError() << std::endl;
		SDL_Quit();
		return 1;
	}
	for (int i = 0; i < 3; ++i)
	{
		SDL_RenderClear(ren);
		SDL_RenderCopy(ren, tex, NULL, NULL);
		SDL_RenderPresent(ren);
		SDL_Delay(10000);
	}

	SDL_DestroyTexture(tex);
	SDL_DestroyRenderer(ren);
	SDL_DestroyWindow(win);
	SDL_Quit();
	return 0;
}

默认SDL2 支持BMP格式图片的加载，示例如上代码，接下来，介绍的是SDL加载其他格式的图片jpeg,png,webp…格式
依赖新的库：SDL_image

https://www.libsdl.org/projects/SDL_image/
下载对应平台的SDL_Image库，我是win平台vs2013开发，所以下载是SDL2_image-devel-2.0.5-VC.zip (Visual C++ 32/64-bit)这个。

与加载BMP方式唯一的不同是改了如下加载函数即可。

	std::string imagePath = "G:\\code\\AudioDemo\\Res\\jpgs\\015.jpg";
	SDL_Surface *bmp = IMG_Load(imagePath.c_str());

完整代码如下：

#include 
#include 
#include 
int main(int argc, char* argv[])
{
	if (SDL_Init(SDL_INIT_VIDEO))
	{
		std::cout << "SDL_Init Error: " << SDL_GetError() << std::endl;
		return 1;
	}
	SDL_Window *win = SDL_CreateWindow("Hello World!", 100, 100, 640, 480, SDL_WINDOW_SHOWN);
	if (win == nullptr)
	{
		std::cout << "SDL_CreateWindow Error: " << SDL_GetError() << std::endl;
		return 1;
	}
	SDL_Renderer *ren = SDL_CreateRenderer(win, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
	if (ren == nullptr)
	{
		SDL_DestroyWindow(win);
		std::cout << "SDL_CreateRender Error: " << SDL_GetError() << std::endl;
		SDL_Quit();
		return 1;
	}
	//std::string imagePath = "G:\\code\\AudioDemo\\Res\\bmps\\childrensday.bmp";
	//SDL_Surface *bmp = SDL_LoadBMP(imagePath.c_str());

	std::string imagePath = "G:\\code\\AudioDemo\\Res\\jpgs\\015.jpg";
	SDL_Surface *bmp = IMG_Load(imagePath.c_str());
	if (bmp == nullptr)
	{
		SDL_DestroyRenderer(ren);
		SDL_DestroyWindow(win);
		std::cout << "SDL_LoadBMP Error: " << SDL_GetError() << std::endl;
		SDL_Quit();
		return 1;
	}
	SDL_Texture *tex = SDL_CreateTextureFromSurface(ren, bmp);
	SDL_FreeSurface(bmp);
	if (tex == nullptr)
	{
		SDL_DestroyRenderer(ren);
		SDL_DestroyWindow(win);
		std::cout << "SDL_CreateTextureFromSurface Error: " << SDL_GetError() << std::endl;
		SDL_Quit();
		return 1;
	}
	for (int i = 0; i < 3; ++i)
	{
		SDL_RenderClear(ren);
		SDL_RenderCopy(ren, tex, NULL, NULL);
		SDL_RenderPresent(ren);
		SDL_Delay(10000);
	}

	SDL_DestroyTexture(tex);
	SDL_DestroyRenderer(ren);
	SDL_DestroyWindow(win);
	SDL_Quit();
	return 0;
}