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From: luj@delta.ecn.purdue.edu (Jun Lu)
Newsgroups: comp.windows.x
Subject: Re: XImages
Message-ID: <1990Dec12.191533.14361@noose.ecn.purdue.edu>
Date: 12 Dec 90 19:15:33 GMT
References: <9012101728.AA23279@test4> <927@attc.UUCP>
Sender: news@noose.ecn.purdue.edu (USENET news)
Organization: Purdue University School of Aeronautics and Astronautics
Lines: 33

In article <927@attc.UUCP> marbru@auto-trol.com (Martin Brunecky) writes:
>   
>   My *observation* is that IF I access image data as BYTES on either
>   SPARC or DECstation, I must assume MSBfirst no matter what the XImage
>   structure says.

Not true(at least for Sparcs). In the case that a image is stored as bytes,
byte_ordering is not important.  You can always specifiey the byte_order
with the macro ImageBteOrder(dpy) -- becasue for byte images, byte_order
does not really matter.(Of course, you can arbitrarily specify the
byte_order as LSBFirst if you insist).

>   IF I access image data as scan-units (32 bits in this case), I must
>   honor the "image byte order".

Agree.

>   What does NOT make sense to me, is that the BYTE order in 32 bit unit
>   is a CLIENT machine feature, not the SERVER machine.

Depends on how you get your images. In the case that the client read the
image from a disk, the image byte_order should be specified according to how
the image is actually stored in the client memory and this byte_ordeing has
nothing do with whether the client is big_endian or little_endian. In the
case the client gets its image by the request XGetImage, the XImage struct
should never be modified and the client should access the image according
the the byte_order/bit_order returned.

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