上面就是一个精灵图，由多个固定间隔的图标组成。利用精灵图的好处就是不必将图标逐个读入内存进行操作。我们可以将精灵图中需要的部分用一个个矩形截取下来，然后再输出到渲染器上。
环境：SDL2 + VC++2015
下面的代码将打开sprite.png，并对相应的操作做出响应。
sprite.png
#include <stdexcept>
#include <string>
#include <iostream>
#include "SDL.h"
#include "SDL_image.h" //屏幕宽度
const int SCREEN_WIDTH = ;
const int SCREEN_HEIGHT = ; //全局窗口和渲染器
SDL_Window *window = nullptr;
SDL_Renderer *renderer = nullptr; //记录SDL错误
void logSDLError(std::ostream &os, const std::string &msg)
{
os << msg << " error: " << SDL_GetError() << std::endl;
} //加载图像材质
SDL_Texture* loadTexture(const std::string &file, SDL_Renderer *ren)
{
SDL_Texture *texture = IMG_LoadTexture(ren, file.c_str());
if (texture == nullptr) logSDLError(std::cout, "LoadTexture");
return texture;
} //根据坐标生成截取区域并复制输出到渲染器
void renderTexture(SDL_Texture *tex, SDL_Renderer *ren, int x, int y, SDL_Rect *clip = nullptr)
{
//目标截面区域初始化，提供目标在渲染器的坐标
SDL_Rect dst; dst.x = x; dst.y = y;
//源截面区域不为空，将其值赋给目标截面
if (clip != nullptr) { dst.w = clip->w; dst.h = clip->h; }
//将截面输出到渲染器
SDL_RenderCopy(ren, tex, clip, &dst);
} int main(int argc, char** argv)
{
//初始化SDL
if (SDL_Init(SDL_INIT_EVERYTHING) == -)
{
std::cout << SDL_GetError() << std::endl;
return ;
} //创建窗口
window = SDL_CreateWindow("Lesson 5",
SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN);
if (window == nullptr)
{
std::cout << SDL_GetError() << std::endl;
return ;
} //创建渲染器
renderer = SDL_CreateRenderer(window, -, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
if (renderer == nullptr)
{
std::cout << SDL_GetError() << std::endl;
return ;
} //创建纹理
SDL_Texture *image = nullptr;
try
{
image = loadTexture("sprite.png", renderer);
}
catch (const std::runtime_error &e)
{
std::cout << e.what() << std::endl;
return ;
} //iW，iH 表示截面宽高
int iW = , iH = ;
//x，y 分别为截面在渲染器输出的坐标
int x = SCREEN_WIDTH / - iW / ;
int y = SCREEN_HEIGHT / - iH / ; //为精灵图设置截面
SDL_Rect clips[]; //初始化截面信息
for (int i = ; i < ; ++i)
{
clips[i].x = i / * iW;
clips[i].y = i % * iH;
clips[i].w = iW;
clips[i].h = iH;
} //表示将要输出的截面
int useClip = ; SDL_Event e;
bool quit = false;
//主循环
while (!quit)
{
//事件轮询
while (SDL_PollEvent(&e))
{
//按右上角的X退出
if (e.type == SDL_QUIT) quit = true; //点击鼠标随机输出截面
if (e.type == SDL_MOUSEBUTTONDOWN) useClip = rand() % ; //使用数字键决定输出截面，分别有1，2，3，4
if (e.type == SDL_KEYDOWN)
{
switch (e.key.keysym.sym)
{
case SDLK_1:
case SDLK_KP_1:
useClip = ;
break;
case SDLK_2:
case SDLK_KP_2:
useClip = ;
break;
case SDLK_3:
case SDLK_KP_3:
useClip = ;
break;
case SDLK_4:
case SDLK_KP_4:
useClip = ;
break;
case SDLK_ESCAPE:
quit = true;
break;
default:
break;
}
}
}
//清空渲染器
SDL_RenderClear(renderer);
//绘制材质
renderTexture(image, renderer, x, y, &clips[useClip]);
//呈现渲染器
SDL_RenderPresent(renderer);
} //释放资源
SDL_DestroyTexture(image);
SDL_DestroyRenderer(renderer);
SDL_DestroyWindow(window); SDL_Quit(); return ;
}