I'm asuming you're using Allegro 5. In case you're actually using Allegro 4, "magic pink" (R: 255, G: 0, B: 255) is the color you want for transparency. If you're using Allegro 5, though, this is the function you want:

void al_convert_mask_to_alpha(ALLEGRO_BITMAP *bitmap, ALLEGRO_COLOR mask_color);

It converts all pixels on an image with a certain color to transparent.

Maybe Allegro automatically picks a bitmap format without Alpha when loading an image that doesn't have an alpha channel. You can override the bitmap format, though. Just call this function before loading your image:

void al_set_new_bitmap_format(int format);

Just pass it any format that supports alpha like ALLEGRO_PIXEL_FORMAT_ANY_WITH_ALPHA, ALLEGRO_PIXEL_FORMAT_ARGB_8888 etc.

I recommend first calling

int al_get_new_bitmap_format(void);

to backup the currently active bitmap format and then restore this format after loading your bitmap (so that all bitmaps loader afterwards will be created with the originally set bitmap format).

I got it to work, I simply had the wrong rgb value. My final question is how come when pass a ALLEGRO_COLOR variable directly into the second arguement of al_convert_mask_to_alpha() it doesnt seem to have effect? It only seems to work when I write al_convert_mask_to_alpha(*, al_map_rgb(short, short, short));

I tried modifying my operation with the info you shared
transparentPixal = al_map_rgb(0.0f, 255.0f, 114.0f);
It did not help
al_convert_mask_to_alpha(bmp, transparentPixal);
It compiles fine, but no transparency, this line however works
al_convert_mask_to_alpha(bmp, al_map_rgb(0.0f, 255.0f, 114.0f));
But I would like to pass a variable as a argument instead, I guess if all else fails I can use a array to store objects rgb values to pass as arguement to al_map_rgb(), but before i succumb to that any suggestions?

You don't need to use floats, unless you use al_map_rgb_f() (in which case you use values from 0.0f to 1.0f). If you use al_map_rgb(), integers will do (ranging from 0 to 255).

Aside from that, nothing wrong with your code. It should work the way you posted it here. Is that the exact code from your game? Can you copy & paste the snippet directly from your game?

As I suggested:

I'm seeing nothing that strikes me as obviously wrong with your code. Are you sure that passing transparentPixal to the function doesn't work and passing al_map_rgb(0, 255, 114) to the function directly DOES work? That is the only thing that is puzzling me. I'm not currently at my home computer, so I can't test the code myself. If you look at transparentPixal in your debugger after asigning the value to it, what does it say? And in case you have access to the Allegro source while debugging, if you step into the call

al_convert_mask_to_alpha(bmp, al_map_rgb(0, 255, 114));

What does the color argument say when looking at it in the debugger?

Also, what OS are you on, what version of Allegro are you using and which compiler did you compile this with?

I don't have too much experience with Linux systems unfortunately, so maybe someone else can provide better help. In any case, two IDEs for Linux I know of are Eclipse and Code::Blocks. Just pick whichever IDE you like best. I haven't worked much with either of those, so I can't give any specific instructions on how to do it, but basically you'll want to find out how to set breakpoints and view the value of a variable. In many IDEs, both things are pretty straight-forward. For example, in Visual Studio you just click a line number to set a breakpoint and hover the mouse over a variable to view its value. I can imagine it's similar with the two aforementioned IDEs, but you'll have to find that out for yourself.

Yeah, I figured as much. But which specific version of Allegro 5? As in, Allegro 5.X.X?

Oh, well spotted! I totally overlooked that! al_map_rgb(a) seems to convert colors by taking its values from an array called "_al_u8_to_float" (using the integer color component value as an index). I can imagine that said array isn't initialized until either Allegro is installed or the graphics system is.

Yes, I can confirm that. The float variants will work without initialization, but converting from integers won't work without calling al_init().