[SDL] SDL_image Image Rendering - SDL 이미지 렌더링

SDL 기본 라이브러리는 BMP 형식의 이미지만 처리할 수 있다. JPG나 PNG 형식을 처리하기 위해서는 SDL_image 라이브러리가 필요하다.

 

우선 SDL 기본 라이브러리로 BMP 이미지를 렌더링 해 보자.

 

#include <iostream>
#include "SDL.h"
 
#pragma comment(lib, "sdl2.lib")
#pragma comment(lib, "sdl2main.lib")
 
int main(int argc, char* argv[]) {
    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
        printf("SDL Initialization Fail: %s\n", SDL_GetError());
        return -1;
    }
 
    SDL_Window* window = SDL_CreateWindow("SDL Test", SDL_WINDOWPOS_UNDEFINED,
        SDL_WINDOWPOS_UNDEFINED, 640, 480, SDL_WINDOW_RESIZABLE);
 
    if (!window) {
        printf("SDL_CreateWindow Error: %s\n", SDL_GetError());
        SDL_Quit();
        return -1;
    }
 
    SDL_Renderer* renderer = SDL_CreateRenderer(window, -1, 0);
 
    SDL_Surface* bmpSurface = SDL_LoadBMP("image.bmp");
    // Load a BMP image from a file path.
    if (bmpSurface == NULL) {
        SDL_DestroyRenderer(renderer);
        SDL_DestroyWindow(window);
        printf("SDL_LoadBMP Error: %s\n", SDL_GetError());
        SDL_Quit();
        return -1;
    }
    SDL_Rect destRect = { 0, 0, bmpSurface->w, bmpSurface->h };
 
    SDL_Texture* texture = SDL_CreateTextureFromSurface(renderer, bmpSurface);
    // Create a texture from an existing surface.
    if (texture == NULL) {
        SDL_FreeSurface(bmpSurface);
        // Free an RGB surface.
        SDL_DestroyRenderer(renderer);
        SDL_DestroyWindow(window);
        printf("SDL_CreateTextureFromSurface Error: %s\n", SDL_GetError());
        SDL_Quit();
        return -1;
    }
    SDL_FreeSurface(bmpSurface);
 
    SDL_Event event;
    bool quit = false;
 
    while (!quit) {
        while (SDL_PollEvent(&event)) {
            switch (event.type) {
            case SDL_QUIT:
                quit = true;
                break;
            case SDL_KEYDOWN:
                printf("Key pressed: %s\n", SDL_GetKeyName(event.key.keysym.sym));
                if (event.key.keysym.sym == SDLK_ESCAPE)
                    quit = true;
                break;
            default:
                break;
            }
        }
 
        SDL_SetRenderDrawColor(renderer, 255, 255, 255, SDL_ALPHA_OPAQUE);
        SDL_RenderClear(renderer);
        SDL_RenderCopy(renderer, texture, NULL, &destRect);
        // Copy a portion of the texture to the current rendering target.
        SDL_RenderPresent(renderer);
    }
 
    SDL_DestroyTexture(texture);
    // Destroy the specified texture.
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    SDL_Quit();
 
    return 0;
}

 

코드를 작성하고 빌드한다.

 

실행하면 윈도우에 이미지가 렌더링 된다.

 

만약 그래픽 카드의 지원을 받을 수 없는 Embedded System 등에서 소프트웨어 방식의 렌더링만 사용할 수 있다면 Texture, Renderer 를 사용하지 않고 Window Surface, BMP Surface 를 사용해 직접 화면에 이미지를 출력할 수 있다.

 

#include <iostream>
#include "SDL.h"
 
#pragma comment(lib, "sdl2.lib")
#pragma comment(lib, "sdl2main.lib")
 
int main(int argc, char* argv[]) {
    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
        printf("SDL Initialization Fail: %s\n", SDL_GetError());
        return -1;
    }
 
    SDL_Window* window = SDL_CreateWindow("SDL Test", SDL_WINDOWPOS_UNDEFINED,
        SDL_WINDOWPOS_UNDEFINED, 640, 480, SDL_WINDOW_RESIZABLE);
 
    if (!window) {
        printf("SDL_CreateWindow Error: %s\n", SDL_GetError());
        SDL_Quit();
        return -1;
    }
 
    SDL_Surface* windowSurface = SDL_GetWindowSurface(window);
    // Get the SDL surface associated with the window.
    // A new surface will be created with the optimal format for the window,
    // if necessary. This surface will be freed when the window is destroyed.
    // Do not free this surface.
    // This surface will be invalidated if the window is resized. After resizing
    // a window this function must be called again to return a valid surface.
    // You may not combine this with 3D or the rendering API on this window.
 
    SDL_Surface* bmpSurface = SDL_LoadBMP("image.bmp");
    if (bmpSurface == NULL) {
        SDL_DestroyWindow(window);
        printf("SDL_LoadBMP Error: %s\n", SDL_GetError());
        SDL_Quit();
        return -1;
    }
 
    SDL_Event event;
    bool quit = false;
 
    while (!quit) {
        while (SDL_PollEvent(&event)) {
            switch (event.type) {
            case SDL_QUIT:
                quit = true;
                break;
            case SDL_KEYDOWN:
                printf("Key pressed: %s\n", SDL_GetKeyName(event.key.keysym.sym));
                if (event.key.keysym.sym == SDLK_ESCAPE)
                    quit = true;
                break;
            default:
                break;
            }
        }
 
        SDL_BlitSurface(bmpSurface, NULL, windowSurface, NULL);
        // Use this function to perform a fast surface copy to a destination surface.
        SDL_UpdateWindowSurface(window);
        // Copy the window surface to the screen. This is the function you use to
        // reflect any changes to the surface on the screen.
    }
 
    SDL_FreeSurface(bmpSurface);
    SDL_DestroyWindow(window);
    SDL_Quit();
 
    return 0;
}

 

코드를 작성하고 빌드한다.

 

윈도우에 이미지가 출력된다.

 

 

 

이번엔 SDL_image를 이용해 JPG, PNG 등의 이미지를 출력해 보자. 아래 링크에서 SDL_image를 다운받고 적당히 설치한다.

SDL Libraries

 

#include <iostream>
#include "SDL.h"
#include "SDL_image.h"
 
#pragma comment(lib, "sdl2.lib")
#pragma comment(lib, "sdl2main.lib")
#pragma comment(lib, "sdl2_image.lib")
 
int main(int argc, char* argv[]) {
    SDL_Init(SDL_INIT_VIDEO);
    SDL_Window* window = SDL_CreateWindow("SDL Test", SDL_WINDOWPOS_UNDEFINED,
        SDL_WINDOWPOS_UNDEFINED, 640, 480, SDL_WINDOW_RESIZABLE);
    SDL_Renderer* renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
    // SDL_RENDERER_SOFTWARE: the renderer is a software fallback
    // SDL_RENDERER_ACCELERATED : the renderer uses hardware acceleration
    // SDL_RENDERER_PRESENTVSYNC : present is synchronized with the refresh rate
    // SDL_RENDERER_TARGETTEXTURE : the renderer supports rendering to texture
    // Note that providing no flags gives priority to available SDL_RENDERER_ACCELERATED
    // renderers.
 
    IMG_Init(IMG_INIT_JPG | IMG_INIT_PNG);
    // Initialize SDL_image.
 
    SDL_Surface* imageSurface = IMG_Load("image.png");
    // Load an image from a filesystem path into a software surface.
    SDL_Texture* texture = SDL_CreateTextureFromSurface(renderer, imageSurface);
    SDL_Rect destRect = { 0, 0, imageSurface->w, imageSurface->h };
 
    SDL_Event event;
    bool quit = false;
 
    while (!quit) {
        while (SDL_PollEvent(&event)) {
            switch (event.type) {
            case SDL_QUIT:
                quit = true;
                break;
            case SDL_KEYDOWN:
                printf("Key pressed: %s\n", SDL_GetKeyName(event.key.keysym.sym));
                if (event.key.keysym.sym == SDLK_ESCAPE)
                    quit = true;
                break;
            default:
                break;
            }
        }
 
        //SDL_SetRenderDrawColor(renderer, 255, 255, 255, SDL_ALPHA_OPAQUE);
        //SDL_RenderClear(renderer);
        SDL_RenderCopy(renderer, texture, NULL, &destRect);
        SDL_RenderPresent(renderer);
    }
 
    SDL_DestroyTexture(texture);
    SDL_FreeSurface(imageSurface);
    IMG_Quit();
    // Deinitialize SDL_image.
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    SDL_Quit();
 
    return 0;
}

 

코드를 입력하고 빌드한다.

 

실행하면 윈도우에 이미지가 렌더링 된다.

 

주석처리된 배경 처리 부분을 아래와 같이 해제하고 알파 채널이 있는 PNG 파일을 렌더링 해 보자.

 

SDL_SetRenderDrawColor(renderer, 0, 0, 255, SDL_ALPHA_OPAQUE);
SDL_RenderClear(renderer);

 

player.png

0.00MB

 

 

 

특별한 처리 없이도 알파 채널이 보존되어 투명한 부분이 잘 표현된다.

 

※ 참고

SDL_image API