How to get integers from ALLEGRO

How to get integers from ALLEGRO_BITMAP

Chris Katko

Member #1,881

January 2002

An ALLEGRO_COLOR struct is four floats.

So how do I get integers? I'm pretty sure my screen isn't a floating point 24-bit display... it's not likely to be stored in OpenGL as floats.

[edit] To be clear, I mean, without the speed penalty of ALLEGRO converting from NATIVE to FLOAT and back to INTEGER. I just want native.

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Edgar Reynaldo

Major Reynaldo

May 2007

You only get an ALLEGRO_COLOR when you al_get_pixel. Don't do that. Just access the memory directly and observe the format it was locked in.

An ALLEGRO_COLOR struct should only be accessed using the al_unmap_rgb(a)(_f) functions.

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Polybios

Member #12,293

October 2010

Lock the bitmap with ALLEGRO_PIXEL_FORMAT_ANY and have a look at the ALLEGRO_LOCKED_REGION you get - format will tell you the native format the driver chose, I think it's been ALLEGRO_PIXEL_ABGR_8888 (or with _LE) for me (32 bits)
Read from ALLEGRO_LOCKED_REGION's data pointer, observing pitch and pixel size
Don't forget to unlock and use ALLEGRO_LOCK_READONLY to avoid reuploading when unlocking