如何在OSX下的SDL / OpenGL应用程序中加载JPG / PNG纹理

Question

i am writing an SDL / OpenGL application that runs under OSX. I have to use existing code which uses the DevIL library for loading JPG and PNG textures. Unfortunately, this works very bad under OS X, so i decided not to use DevIL at all, and rewrite the respective parts of the application using another library. I want to keep it flexible (DevIL can handle a lot of image formats) and easy to use. Is there a good replacement for DevIL that you can recommend? The application is entirely written in C++.

Answer 1

Have a look at the SDL_image library. It offers functions like IMG_LoadPNG that load your picture "as an" SDL_Surface. Since you already work with SDL this should fit quite well in your program.

Sample taken from the SDL_image documentation :

// Load sample.png into image
SDL_Surface* image = IMG_Load("sample.png");
if (image == nullptr) {
    std::cout << "IMG_Load: " << IMG_GetError() << "\n";
}

Answer 2

SDL 2 SDL_image minimal runnable example

main.c

#include <stdlib.h>

#include <SDL2/SDL.h>
#include <SDL2/SDL_image.h>

int main(void) {
    SDL_Event event;
    SDL_Renderer *renderer = NULL;
    SDL_Texture *texture = NULL;
    SDL_Window *window = NULL;

    SDL_Init(SDL_INIT_TIMER | SDL_INIT_VIDEO);
    SDL_CreateWindowAndRenderer(
        500, 500,
        0, &window, &renderer
    );
    IMG_Init(IMG_INIT_PNG);
    texture = IMG_LoadTexture(renderer, "flower.png");
    while (1) {
        SDL_RenderCopy(renderer, texture, NULL, NULL);
        SDL_RenderPresent(renderer);
        if (SDL_PollEvent(&event) && event.type == SDL_QUIT)
            break;
    }
    SDL_DestroyTexture(texture);
    IMG_Quit();
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    SDL_Quit();
    return EXIT_SUCCESS;
}

GitHub upstream .

Compile and run:

sudo apt-get install libsdl2-dev libsdl2-image-dev
gcc -std=c99 -o main -Wall -Wextra -pedantic main.c -lSDL2 -lSDL2_image
./main

Outcome:

Tested on Ubuntu 16.04, GCC 6.4.0, SDL 2.0.4, SDL Image 2.0.1.

Answer 3

Take a look at freeimage . It supports all major formats and is easily built with macports. Nice to work with as well. Auto-detects image format etc.

FREE_IMAGE_FORMAT format = FreeImage_GetFileType(filename.c_str(), 0);
FIBITMAP *bitmap = FreeImage_Load(format, filename.c_str());
if (!bitmap)
{
    LOG_ERROR("Unable to load texture: " + filename);
    return false;
}
mlWidth = FreeImage_GetWidth(bitmap);
mlHeight = FreeImage_GetHeight(bitmap);
glGenTextures(1, &mpTextures[0]);
glBindTexture(GL_TEXTURE_2D, mpTextures[0]);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S,     GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T,     GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, mlWidth, mlHeight, 0, GL_BGRA, GL_UNSIGNED_BYTE,
       (GLvoid*)FreeImage_GetBits(bitmap));
FreeImage_Unload(bitmap);

Answer 4

If you're on Mac OS anyway, why not just use CGImageSource to do the loading? OS X natively supports loading many file formats including PNG and JPEG.