Why am I failing to initialize SDL_image? - c

Question

This is an updated post. Someone asked me to do a minimal reproducible example, which did help a lot. This program opens a window, but does not display a PNG image as I would like it to do.
The compiler gives me no errors, however my error message for SDL_Init does.
What could be the reason that I am failing to initialize SDL_Image?
// std
#include <stdio.h>
// sdl
#include <SDL2/SDL.h>
#include <SDL2/SDL_image.h>
int main (int argc, char* argv[])
{
// ----- Initialize SDL
if (SDL_Init(SDL_INIT_VIDEO) != 0)
{
fprintf(stderr, "SDL could not initialize\n");
return 1;
}
if (IMG_Init(IMG_INIT_PNG) != 0)
{
fprintf(stderr, "SDL_image could not initialize\n");
/********
I GET THIS ERROR
********/
}
// ----- Create window
SDL_Window* window = SDL_CreateWindow("Window", SDL_WINDOWPOS_CENTERED,
SDL_WINDOWPOS_CENTERED,
800,
600,
0);
if (!window)
{
fprintf(stderr, "Error creating window.\n");
return 2;
}
SDL_Renderer *renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
SDL_Surface *image_surface = NULL;
image_surface = IMG_Load("button_randomize.png");
if(image_surface == NULL)
{
printf("Cannot find image\n"); // This line is not executed
SDL_Quit();
}
SDL_Texture *image_texture = SDL_CreateTextureFromSurface(renderer, image_surface);
SDL_FreeSurface(image_surface);
// ----- Main loop
int quit = 0;
while (quit == 0)
{
SDL_Event windowEvent;
while (SDL_PollEvent(&windowEvent))
{
if (windowEvent.type == SDL_QUIT)
{
quit = 1;
break;
}
}
SDL_Rect image_rect = {50, 50, 120, 32};
SDL_RenderCopy(renderer, image_texture, NULL, &image_rect);
}
// ----- Clean up
IMG_Quit();
SDL_Quit();
return 0;
}
Output:
SDL_image could not initialize
build command:
gcc -std=c11 -Wall -o obj/main.o -c src/main.c
gcc -std=c11 -Wall -o my_program obj/main.o -lSDL2 -lGL -lGLEW -lm -lSDL2_image
I have tried changing the SDL_Init flags. I even tried to change the IMG_Init flag to IMG_INIT_JPG (and testing with a .jpg image of course), but no luck.

Answer 1

There are two issues in this example:
IMG_Init() returns a bitmask of all the currently initted image loaders instead of 0 on success (this is why you get the error message)
You do not call SDL_RenderPresent() after drawing on the renderer (this is why you can't see anything)
Here is an example on how to init SDL_Image from the SDL2_image documentation:
// load support for the JPG and PNG image formats
int flags = IMG_INIT_JPG | IMG_INIT_PNG;
int initted = IMG_Init(flags);
if ((initted & flags) != flags) {
printf("IMG_Init: Failed to init required jpg and png support!\n");
printf("IMG_Init: %s\n", IMG_GetError());
// handle error
}
And to make the image visible add this to the end of the loop:
SDL_RenderPresent(renderer);