C ++ Allegro 5.0.8-al_load_bitmap（）在Linux上返回NULL

Question

I'm developing a game in Allegro 5.0.8, and everything was going well, until i tried compiling it and running it on Linux (Mint 14)...so i did sime tests;

#include <allegro5/allegro.h>
#include <allegro5/allegro_image.h>
#include <iostream>

int main(void)
{
    al_init();
    ALLEGRO_DISPLAY *screen = al_create_display(800, 600);
    al_init_image_addon();

    ALLEGRO_PATH *path = al_get_standard_path(ALLEGRO_RESOURCES_PATH);
    al_set_path_filename(path, "players.png");
    ALLEGRO_BITMAP *img = al_load_bitmap(al_path_cstr(path, '/'));

    if (img == NULL)
        std::cout << al_path_cstr(path, '/') << std::endl;

    al_draw_bitmap(img, 0, 0, 0);
    al_flip_display();

    while (true){}
    return 0;
}

this example compiles just fine, but the line

ALLEGRO_BITMAP *img = al_load_bitmap(al_path_cstr(path, '/'));

returns NULL . On the other hand, the line

std::cout << al_path_cstr(path, '/') << std::endl;

prints the exact absolute path of the image.

What am i doing wrong?

Answer 1

i have libpng12-0 ..but not libpng12-dev...should i install that too??

After you install libpng12-dev, you'll need to rebuild Allegro. The output of cmake tells you whether or not PNG is supported.

Once you rebuild Allegro with PNG support, it will work assuming your PNG file is not too big to load onto your video card.