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maximum size to al_create_bitmap
The Master
Member #4,498
April 2004
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Allegro5 question:

I'm working on loading a tile set into a single bitmap, and then drawing regions of this bitmap as required. It was the simplest and most straightforward approach.

But I seem to be having a problem. I've saved the tile set into a custom format made with TileStudio (which is awesome by the way), and so I've written code that loads it into an Allegro5 bitmap structure. I do this by creating a new bitmap, and then loading the pixel colour components from the file and using al_put_pixel. Now I know this all works, because I've seen it.

But it gets to when I'm actually creating the bitmap. Sometimes (most of the time but not all) al_create_bitmap will cause a weird exception to be thrown elsewhere in the program. That is, the code will execute until al_create_bitmap, and then it'll throw an exception. But the call stack will in fact point to a different part of the program (some where inside the NSApplication object - I'm using Mac OS X).

I've concluded, but I'm not entirely sure, that this is being caused by me asking for a massive bitmap. 48 tiles, each tile 32x32x32bits. So I was curious if there is an upper limit on the permitted size of a bitmap (independent of the available memory).

Let me know :)

We can only do what we feel is right each moment as we live it.

Evert
Member #794
November 2000
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That is, the code will execute until al_create_bitmap, and then it'll throw an exception. But the call stack will in fact point to a different part of the program (some where inside the NSApplication object - I'm using Mac OS X).

That's the main thread, but your program runs from a secondary thread. You need to switch to one of the other threads to find the correct point where the program crashes (I can never quite remember which thread I want, but you can easily tell by trying them all because most of the tracebacks will not make sence).

Quote:

I've concluded, but I'm not entirely sure, that this is being caused by me asking for a massive bitmap. 48 tiles, each tile 32x32x32bits. So I was curious if there is an upper limit on the permitted size of a bitmap (independent of the available memory).

Yes, if it's a video bitmap, it must be smaller than the largest texture size. If you do a 32 by 48*32 bitmap, you may overrun that. This is less likely if you do 3*32 by 16*32.

Matthew Leverton
Supreme Loser
January 1999
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You can query the maximum size allowed via al_get_new_display_option with ALLEGRO_MAX_BITMAP_SIZE.

Evert said:

if you do a 32 by 48*32 bitmap, you may overrun that. This is less likely if you do 3*32 by 16*32.

In other words, make your tile bitmap square. The longest side is what determines whether or not it will fit into a video bitmap. The same card that doesn't support 1025x32 might support 1024x1024.

The Master
Member #4,498
April 2004
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Well, i think this is worthy of a bug report in the MacOSX port. i'm still having this problem.

[EDIT] it's not just appearing in al_create_bitmap. sometimes it shows up in al_set_target_bitmap. sometimes it shows up in al_fclose.

We can only do what we feel is right each moment as we live it.

Edgar Reynaldo
Member #8,592
May 2007
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Post backtraces of when it occurs, and try examining local variables in the line of code that crashes. Also, run a debug version of your program linked to the debugging version of Allegro. That will create an allegro.log file that may have some clues as well.

Evert
Member #794
November 2000
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Well, i think this is worthy of a bug report in the MacOSX port. i'm still having this problem.

There's no OS X specific code in al_create_bitmap(), it's the same code used on other OpenGL-based ports. So if there is a problem with it, it should show up there too.

Quote:

it's not just appearing in al_create_bitmap. sometimes it shows up in al_set_target_bitmap. sometimes it shows up in al_fclose.

That sounds like you are overwriting memory that you shouldn't due to a bad pointer.

The Master
Member #4,498
April 2004
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ok, i'll triple check my loading and allocation. might use vectors or something instead of the new operator

[EDIT] Now this is freaking weird. I changed my data allocation methods from 'new' to 'std::vector'. and it still shows the same bad alloc error: exact same line number, different code.

We can only do what we feel is right each moment as we live it.

Edgar Reynaldo
Member #8,592
May 2007
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Why don't you post the code you are using? We can't find any errors you might be making without seeing the code you are using. If your code is throwing a std::bad_alloc exception, you are asking for too much memory. Show code.

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