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--- Fred H <[EMAIL PROTECTED]> wrote:
> From Fred H Tue Aug 28 16:43:59 2001
> Received: from [142.22.16.53] by
> web12703.mail.yahoo.com via HTTP; Tue, 28 Aug 2001
> 16:44:00 PDT
> Date: Tue, 28 Aug 2001 16:43:59 -0700 (PDT)
> From: Fred H <[EMAIL PROTECTED]>
> Subject: Re: Idrisi-L : reading .img file with my
> own code
> To: Wei Luo <[EMAIL PROTECTED]>
> In-Reply-To:
>
<[EMAIL PROTECTED]>
> MIME-Version: 1.0
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>
>
> --- Wei Luo <[EMAIL PROTECTED]> wrote:
> > --- Start of Idrisi List message
> > Hi all,
> >
> > I have a question regarding reading IDRISI .img
> > files. I want to read .img
> > files with my own code--I am using Visual Basic.
>
> Object pascal (Delphi) or C are much better for this
> type of work. Their code is much faster to execute
> than VB. BTW, that's one of the reasons why Clark
> Labs
> dumped VB in favour of Delphi. The latest versions
> of
> Idrisi are written in Delphi.
>
> > I tried to open my .img
> > file with Notepad, but it's not illegible at all.
>
> Of course not, it probably was in binary or packed
> binary format.
>
> > How can I convert .img
> > file into an ASCII format that is easily readible
> > with by own code?
>
> Why convert to ascii? Not only will the file sizes
> grow astronomically, but manipulation of the file it
> self will be much slower. Just read the binary file
> as is. Best and easiest thing to do is to work with
> binary files only. Packed binary is nice, but a
> little more work to decode the RLE (run-length
> encoding) compression(?) it uses.
>
> Now doing this programming requires a bit of
> homework
> on how to read binary files. I suspect that given
> your attempt to read a binary file with an ascii
> editor means you are probably pretty new to
> programming. No problem, we all started out as
> newbies, but you are going to have to do some
> research. Reading a binary file is dead easy in
> Delphi, and probably fairly simple in VB, though I
> am
> not sure how well it handles streams. In any event,
> I
> suggest you go on to the VB newsgroups and ask for a
> simple example of reading a binary file.
> Since these kinds of questions have been asked many
> time before go on to google first
> (http://groups.google.com/advanced_group_search) and
> search for "reading binary files" in the VB
> newsgroups
> (*.VB.*)
>
> Here check this link (all on *one* line)
>
http://groups.google.com/groups?as_q=reading%20binary%20files&as_ugroup=*.VB.*&lr=lang_en
>
> There are tons of examples.
>
> Idrisi has documented the format of the img file in
> its manuals. To read a img file you need to also
> read
> the ascii based DOC file. It tells you the number
> of
> rows and cols, the format of the file, whether its
> byte, real or integer, etc.
>
> Since you are using VB, you might also want to
> consider using an OCX there was one on the net a few
> years ago (http://www.inovagis.org). Also, check
> out
> http://www.clarklabs.org/13DNLDS/13dnlds.htm
> for information on the Idrisi API. Idrisi32 can act
> as
> a com server you can control from VB or any com
> compliant compiler. These solutions, however, will
> not
> match the performance you can achieve by coding a
> map
> reader yourself, but you may find them easier to
> implement.
>
> Good Luck,
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