[directfb-dev] Re: Help me please! About 4bits pixel format.

["Henric Andersson" <ha@thedudes.nu>]

Sorry about the previous mail, wrong button combo :)

>Hi,
>So sorry to bother you, but I really want to implement 4bits pixel
>format for DirectFB. The source code of DirectFB almost drives me crazy.
>Could you please give me some more hint or information?
>Until now, I did not understand the structure of DirectFB clearly,
>especially the surface memory management. In my understanding, a surface
>may occupy a block of memory itself or share a block of memory with
>other surface, ie. a sub surface. Am I right? Then, for example if I
>alloc a sub surface from an odd x coordination within the father
>surface, i.e. (3,4), the memory offset of the sub surface will be 1.5
>bytes, but it's impossible! There are many other similar problems in
>DirectFB to prevent me implementing 4bpp format. But it is very

It is possible to use uneven X coordinates. You have to work at a bit level
though. So, if you would highlight the first pixel of a row, you would only
manipulate the first 4 bits. The next pixel would use the higher 4 bits of
the same byte, the next (3rd) pixel would use the lower 4 bits of the second
byte, and so on.

Hope it helps...

/Henric



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