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From: mouse@LARRY.MCRCIM.MCGILL.EDU
Newsgroups: comp.windows.x
Subject: Re:  Can some one help me with Image package
Message-ID: <9010240903.AA15894@Larry.McRCIM.McGill.EDU>
Date: 24 Oct 90 09:03:12 GMT
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 39

>>> The XPutPixel is not too bad to use as it is very smart about 8 and
>>> 1 bit images.  [...]  We have found the that slowness is tolerable
>>> knowing that an application will always work with any depth and
>>> bit-byte ordering.
>> If you're trying to be interactive it's *not* tolerable.  I get
>> around this by defining my own image format and slamming it into the
>> XImage structure.  The code that transforms into server-native
>> format is much more efficient than the PutPixel/GetPixel code so
>> there's a big jump in throughput.
> Yes we did this originally, too, but found that some servers do *NOT*
> accept any old format that you stuff into an XImage structure.  Does
> an X server have to accept any XImage structure (but do it slowly if
> it does not match the hardware format)?

According to my skimming of the protocol document, images must be
presented to the server in its native format (which the client finds
out about at connection setup).  It is up to the client to do any
reordering necessary.

However, the Xlib document says, when talking about XImage structures,

	You may request that some of the members (for example,
	height, width, and xoffset) be changed when the image is
	sent to the server. That is, you may send a subset of the
	image.  Other members (for example, byte_order, bitmap_unit,
	and so forth) are characteristics of both the image and the
	server. If these members differ between the image and the
	server, XPutImage makes the appropriate conversions.

So if this isn't happening, there's a bug in XPutImage, or perhaps the
server is rejecting data which in fact actually conforms to the format
it has requested.  Either one calls for a bug report - but make sure
you have it right which one it is; an erroneous bug report is often
almost worse than no bug report at all.

					der Mouse

			old: mcgill-vision!mouse
			new: mouse@larry.mcrcim.mcgill.edu