SDL无法正确下载libpng16-16dll?

Question

我在vs里使用sdl的第三方库SDL_image的时候，库及lib文件引用正常，待显示的图片资源也放置在了合适的位置，在执行exe文件的时候报错

LoadTexture error: Failed loading libpng16-16.dll: 鎵句笉鍒版寚瀹氱殑妯″潡銆

可是它所依赖的dll文件确实已经正确放在和.cpp同级的目录下了呀。。

顺便付一下我的代码

#include <string>
#include <iostream>
#include <SDL.h>
#include <SDL_image.h>

//Screen attributes
const int SCREEN_WIDTH = 640;
const int SCREEN_HEIGHT = 480;

void logSDLError(std::ostream &os, const std::string &msg){
    os << msg << " error: " << SDL_GetError() << std::endl;
}

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;
}

void renderTexture(SDL_Texture *tex, SDL_Renderer *ren, int x, int y, int w, int h){
    //Setup the destination rectangle to be at the position we want
    SDL_Rect dst;
    dst.x = x;
    dst.y = y;
    dst.w = w;
    dst.h = h;
    SDL_RenderCopy(ren, tex, NULL, &dst);
}

void renderTexture(SDL_Texture *tex, SDL_Renderer *ren, int x, int y){
    int w, h;
    SDL_QueryTexture(tex, NULL, NULL, &w, &h);
    renderTexture(tex, ren, x, y, w, h);
}
int main(int, char**){
    //Start up SDL and make sure it went ok
    if (SDL_Init(SDL_INIT_VIDEO) != 0){
        logSDLError(std::cout, "SDL_Init");
        return 1;
    }

    SDL_Window *window = SDL_CreateWindow("Lesson 4", SDL_WINDOWPOS_CENTERED,
        SDL_WINDOWPOS_CENTERED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN);
    if (window == nullptr){
        logSDLError(std::cout, "CreateWindow");
        SDL_Quit();
        return 1;
    }
    SDL_Renderer *renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
    if (renderer == nullptr){
        logSDLError(std::cout, "CreateRenderer");
        //cleanup(window);
        SDL_Quit();
        return 1;
    }

    SDL_Texture *bg = loadTexture("buttonBg.bmp", renderer);
    SDL_Texture *boggle = loadTexture("loggle.bmp", renderer);
    SDL_Texture *bulbOff = loadTexture("background.png", renderer);
    SDL_Texture *bulbOn = loadTexture("bulb_off.bmp", renderer); 

    if (bg == nullptr){
        //    cleanup(image, renderer, window);
        IMG_Quit();
        SDL_Quit();
        return 1;
    }

    int iW, iH;
    int bW, bH;
    int moveDis;
    SDL_QueryTexture(bg, NULL, NULL, &iW, &iH);
    SDL_QueryTexture(bulbOff, NULL, NULL, &bW, &bH);

    int x = SCREEN_WIDTH / 2 - iW / 2;
    int y = SCREEN_HEIGHT / 2 + iH;
    int bX = SCREEN_WIDTH / 2 - bW / 2;
    int bY = SCREEN_HEIGHT / 2 - 220;
    moveDis = iW;
    /*
    每次显示图画的时候必须清理一次render渲染器
    然后调用renderTexture
    最后用renderPresent显示图画
    */
    //Rendering
    SDL_RenderClear(renderer);
    //Draw the image
    renderTexture(bg, renderer, x, y);
    renderTexture(boggle, renderer, x + 30, y + 10);
    renderTexture(bulbOff, renderer, bX, bY);
    //Update the screen
    SDL_RenderPresent(renderer);
    //Our event structure

    int flag = 0; //控制灯泡亮灭
    int flagDown = false;
    SDL_Event e_down;
    SDL_Event e_move;
    //For tracking if we want to quit
    bool quit = false;
    int xButton = x;
    int yButton = y;
    while (!quit){
        //Read any events that occured, for now we'll just quit if any event occurs
        while (SDL_PollEvent(&e_down)){
            if (e_down.type == SDL_MOUSEBUTTONDOWN)
                //当事件为触屏
            {
                std::cout << "down";
                flagDown = true;
            }

        }

        while (SDL_PollEvent(&e_move)){
            if (e_down.type == SDL_MOUSEMOTION && flagDown)
                //当事件为触屏
            {
                std::cout << "OK";
            }

        }

    }


    //Destroy the various items
    //cleanup(image, renderer, window);
    IMG_Quit();
    SDL_Quit();
    return 0;
}

请问到底是哪里有问题，求指导？？