Why doesn't my bmp save with transparent background? [duplicate]

I have the following .bmp file called mapa.bmp

As you can see, from the embedded picture, my background is fully transparent.
I made sure to check and my Image->Mode is set to RGB as well.

and I saved it using the default options:

All seems fine and dandy, right?

However, if I use the picture anywhere, or even re-open it with photoshop, the transparent background is lost and opened with white background.

Saving the file as .png works fine, but sadly I need to use .bmp, .ico or .jpg format

Any idea what could be the cause?

1 Answer

As pointed out in the duplicate question, while .bmp supports transparency - technically - it is not entirely recommended to.

In case you can't use .png (like I couldn't), it's best to use .jpeg 2000 or .gif format as a substitute