Hey guys!
First post here, hello everyone
I recently started using Allegro 5, i need to access the pixel table of loaded BMP file.I know you could do it with Allegro 4 by line parameter, is there a way to do that in Allegro 5?
Thanks in advance

If you don't use a memory bitmap, your data resides on the GPU side of things. Therefore, you should use bitmap locking, as reading / writing from/to the GPU is slow to do per-pixel. What it does is to cache (parts of) the bitmap in memory (CPU side of things). From there, you can also access the data directly via the ALLEGRO_LOCKED_REGION.

See al_lock_bitmap, al_unlock_bitmap and ALLEGRO_LOCKED_REGION.

In theory, the fastest way would probably be to do it directly on the GPU in parallel.

In practice when using Allegro, you can request a certain pixel format (typically ALLEGRO_PIXEL_FORMAT_ABGR_8888) when locking and then just access it via the data pointer of the ALLEGRO_LOCKED_REGION al_lock_bitmap returns. Allegro will convert it for you when necessary.

Allegro 5 will give you access to a memory copy of the video memory. That's what happens when you lock a video bitmap. An ALLEGRO_LOCKED_REGION has a pointer to the data, a format, a pitch, and a pixel size. You use these to read and write the data.

Don't assume pitch is equivalent to pixel size times line width. It may differ, it may be different, or it may be negative.

You probably want to lock the region in a 24 or 32 bit format. Allegro will convert the bitmap to and from the format you lock it in.

@Kajkacz:
So you are writing / have to write a software renderer?