A5 can't get load_bitmap to find image

no-reply@allegro.cc (kyle motherwell) — Sun, 20 Mar 2011 04:58:47 +0000

Hey people, I was here a while ago learning A4 then I took a short break, I came back just a few days ago and A5 appears to have been out for a bit, I had a look at it and looked at some examples and such, I wanted to see if I could load an image and draw it to the screen so I created a bitmap object and set it to NULL then I tried to assign it an image from my HDD called bob, which is a bitmap image. The problem is when the program runs I get an exception :

First-chance exception at 0x00000000 in AllegroProject.exe: 0xC0000005: Access violation.

Unhandled exception at 0x00000000 in AllegroProject.exe: 0xC0000005: Access violation.

I presume this is because the image assign fails because it can't find my image, I tried quite a few things to get this working, first I tried an absolute path, which did not work, then I put it in the same folder as the .exe that also did not work, I also tried something using the path "hack" someone was calling it although I only partially understood what it was doing and it kept failing at compile so I left it.

So I would really appreciate it if someone could tell me whats wrong with my program.

Line that is the main culprit: al_load_bitmap("bob.bmp");

no-reply@allegro.cc (Trent Gamblin) — Sun, 20 Mar 2011 05:08:52 +0000

Please post some source code. Use tags.

no-reply@allegro.cc (Matthew Leverton) — Sun, 20 Mar 2011 05:13:39 +0000

Call al_init_image_addon() first.

no-reply@allegro.cc (kyle motherwell) — Sun, 20 Mar 2011 05:16:48 +0000

To mat, I just put it in now and it still seems to give exceptions.

#SelectExpand
   1#include "stdafx.h"
   2#include 
   3#include 
   4#include 

   6int main(int argc, char **argv)
   7{
   8
   9//Create a display and an event queue
 ALLEGRO_DISPLAY *display = NULL;
 ALLEGRO_EVENT_QUEUE *event_queue = NULL;
 ALLEGRO_BITMAP * testBMP = NULL;
  13
 al_init_image_addon();
  15
  16al_load_bitmap("bob.bmp");
  17
 if(!testBMP)
 {
fprintf(stderr,"failed to initialize testBMP!\n");
return -1;
  22
 }
  24
  25
 if(!al_init_image_addon())
 {
fprintf(stderr,"failed to initialize image addon!\n");
return -1;
  30
 }
  32

  34

//Test if allegro failed to initiliaze, if it did print a message to the console and leave with error code -1
 if(!al_init()) {
    fprintf(stderr, "failed to initialize allegro!\n");
    return -1;
 }
//Set the display by assisnging it the properties returned from the function al_create_display(640, 480) this sets the display to a resoloution of 640x480
 display = al_create_display(640, 480);
  43
 //check to see if the display was properly set
 if(!display) {
    fprintf(stderr, "failed to create display!\n");
    return -1;
 }

 //Create an even queue, event queues can be filled with different evens that happen from sources, sources include keyboard, mouse and display, we will use display
 event_queue = al_create_event_queue();
  52
 //We check if the queue was set properly
 if(!event_queue) {
    fprintf(stderr, "failed to create event_queue!\n");
    al_destroy_display(display);
    return -1;
 }

 //We set the queue to watch all the events from the source, our source is the display, so resizing or closing the window would be an event for the display
 al_register_event_source(event_queue, al_get_display_event_source(display));

 //We clear the screen to the colour black
 al_clear_to_color(al_map_rgb(0,0,0));

 //We swap the drawing buffer to show our changes since we last swapped buffers, search up double buffering to find out more about what this means
 al_flip_display();

  69
 while(1)
 {
   //We createa an event to hold the event
    ALLEGRO_EVENT ev;
  //A timeout to be initiliased 
    ALLEGRO_TIMEOUT timeout;
  //Here we initliase timeout and set it to 0.06, or 60 miliseconds
    al_init_timeout(&timeout, 0.06);

  //Here the bool is assigned either true of false depending if the event queue is updated with an event or it gets set to false if the timeout occurs before the event finishes.
    bool got_event = al_wait_for_event_until(event_queue, &ev, &timeout);

  //We check if the event was close
    if(got_event && ev.type == ALLEGRO_EVENT_DISPLAY_CLOSE) {
  84
    //This ends the program loop, closing the program
       break;
    }

  //Clear to black and swap buffers
    al_clear_to_color(al_map_rgb(0,0,0));
    al_flip_display();
 }

 //Destroy display object and queue object
 al_destroy_display(display);
 al_destroy_event_queue(event_queue);

  98
 return 0;
 100}

no-reply@allegro.cc (Trent Gamblin) — Sun, 20 Mar 2011 05:18:18 +0000

You've got it in there twice now, both in the wrong place. Before you use any other allegro functions, call al_init.

no-reply@allegro.cc (Matthew Leverton) — Sun, 20 Mar 2011 05:21:17 +0000

Call load bitmap after initializing Allegro, after initializing the image addon, and after creating the display. Use an absolute path until you know for sure it is working.

Also, your test is bogus because you never assign the value of load_bitmap to anything.

no-reply@allegro.cc (kyle motherwell) — Sun, 20 Mar 2011 05:33:47 +0000

Forgive me for how messy and badly done it all is, I done it pretty quickly and didn't see what I had done wrong. I fixed the mistakes (not all of them I'm sure) and now my test code runs and tells me that it cannot initiliaze the image. I used a absolute path too.

#SelectExpand
  1#include "stdafx.h"
  2#include 
  3#include 
  4#include 

  6int main(int argc, char **argv)
  7{
  8
  9//Create a display and an event queue
 ALLEGRO_DISPLAY *display = NULL;
 ALLEGRO_EVENT_QUEUE *event_queue = NULL;
 ALLEGRO_BITMAP * testBMP = NULL;
 13
 14//Test if allegro failed to initiliaze, if it did print a message to the console and leave with error code -1
 if(!al_init()) {
    fprintf(stderr, "failed to initialize allegro!\n");
    return -1;
 }
//Set the display by assisnging it the properties returned from the function al_create_display(640, 480) this sets the display to a resoloution of 640x480
 display = al_create_display(640, 480);
 21
 //check to see if the display was properly set
 if(!display) {
    fprintf(stderr, "failed to create display!\n");
    return -1;
 }
 27
  testBMP = al_load_bitmap("C:\Users\Kyle\Desktop\kyle-and-liams-project\AllegroProject\bob.bmp");
 29
    if(!testBMP)
 {
fprintf(stderr,"failed to initialize testBMP!\n");
return -1;
 34
 }

 //Create an even queue, event queues can be filled with different evens that happen from sources, sources include keyboard, mouse and display, we will use display
 event_queue = al_create_event_queue();
 39
 //We check if the queue was set properly
 if(!event_queue) {
    fprintf(stderr, "failed to create event_queue!\n");
    al_destroy_display(display);
    return -1;
 }
 46

//We set the queue to watch all the events from the source, our source is the display, so resizing or closing the window would be an event for the display
 al_register_event_source(event_queue, al_get_display_event_source(display));

 //We clear the screen to the colour black
 al_clear_to_color(al_map_rgb(0,0,0));

 //We swap the drawing buffer to show our changes since we last swapped buffers, search up double buffering to find out more about what this means
 al_flip_display();

 57
 while(1)
 {
   //We createa an event to hold the event
    ALLEGRO_EVENT ev;
  //A timeout to be initiliased 
    ALLEGRO_TIMEOUT timeout;
  //Here we initliase timeout and set it to 0.06, or 60 miliseconds
    al_init_timeout(&timeout, 0.06);

  //Here the bool is assigned either true of false depending if the event queue is updated with an event or it gets set to false if the timeout occurs before the event finishes.
    bool got_event = al_wait_for_event_until(event_queue, &ev, &timeout);

  //We check if the event was close
    if(got_event && ev.type == ALLEGRO_EVENT_DISPLAY_CLOSE) {
 72
    //This ends the program loop, closing the program
       break;
    }

  //Clear to black and swap buffers
    al_clear_to_color(al_map_rgb(0,0,0));
    al_flip_display();
 }

 //Destroy display object and queue object
 al_destroy_display(display);
 al_destroy_event_queue(event_queue);

 86
 return 0;
 88}

no-reply@allegro.cc (Matthew Leverton) — Sun, 20 Mar 2011 05:35:43 +0000

The answer is in my previous post.

Edit: And use '/' or '\\' for path separators. A single backslash will cause problems.

no-reply@allegro.cc (kyle motherwell) — Sun, 20 Mar 2011 05:48:28 +0000

Thanks, it was the slashes that were causing the problem.