>At 8:17 AM +1000 on 12/20/00, Robert (actually) wrote:
>>  > One can print out a number in Hex using PRINT HEX$(256), etc.
>>>
>>  > How does one get the number back out of Hex'ed data?

Heather replies:
>I was going to mention this before my ISP crashed.

>The original question was about writing hex data to a file to create
>a TIFF header and also read that data back.

>Unless I misunderstand what has been said in this thread, it sounds
>like you are trying to read and write HEX strings in the data fork.


That is correct.

>Robert Covington's original post on TIFF code shows this to write the header:
>
>/* Write the header */
>    WriteHexString(fptr,"4d4d002a");
>/* Little endian & TIFF identifier */
>
>Instead of dealing with strings, it would seem easier to write the
>hex data directly.

Yes, that is what I  was after.  :)

>Something like this would write the header:
>//little endian header
>DIM headerIBM&`: headerIBM& = 0x4949002a // II
>
>// big endian header
>DIM headerMAC&`: headerIBM& = 0x4d4d002a // MM

>OPEN "D",#1,"SomePicture.tiff",1,tempVRef,tempDirID
>WRITE #1, headerMAC&`
<snip>
>Could be done like this in FB^3:
<snip>
>Reading the data back should be pretty simple, unless I don't have a
>clue what Robert is doing.


Thank you for that exposition. Bourke's writing of the TIFF code is a
little different than others do it. He puts the majority of tags after the
image as a footer, whereas most of the programs I encounter have them all
up top.

But that is pretty much what I was wanting to know as far as translating
his code.

Reading the data back in is simple, as long as your images contain the tags
you look for.

However, after a read of the TIFF specs, they mention that accounting for
all the tag variations by any one reader is a difficult proposition.
Graphic Converter does great I can vouch, my corrupted TIFF files still got
read when Photoshop barfed.

However, I take the easy route for reading TIFF, and use Quicktime. The
problem I had all night that elicited Wahoo-ville, is that the resolution
info was getting written as a long, and it was supposed to be a rational.
Once that parameter got fixed, suddenly Quicktime stopper barfing when
reading the files.

Thank you Heather, for your time and code help in understanding this
hex'ing problem.

Robert Covington