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Path: utzoo!watmath!clyde!burl!ulysses!gatech!seismo!mcvax!frankk
From: frankk@mcvax.UUCP (Frank Kuiper)
Newsgroups: net.micro.mac
Subject: Thunderscan grey map image and other questions.
Message-ID: <914@mcvax.UUCP>
Date: Wed, 11-Dec-85 07:37:36 EST
Article-I.D.: mcvax.914
Posted: Wed Dec 11 07:37:36 1985
Date-Received: Fri, 13-Dec-85 08:34:07 EST
Reply-To: frankk@mcvax.UUCP (Frank Kuiper)
Organization: CWI, Amsterdam
Lines: 57
Fcc: inbox
cc: marjo


A colleague of mine (Marjo) is trying to understand the file
format of a Thunderscan file. She wants to write a program to 
manipulate the data for a scanned image. The image she wants to
read consists of a photo with much grey values, and on that photo
are certain spots. She wants to do statistical calculations on the
size and the number of those spots.
Therefore she wants to know (and I as well) how to interpret
the scanned-image-file.

In the user gide (on page 57) the header of the file is specified.
We understand most of it, but here are our problems:

1) Offset 2: bounding rectangle (8 bytes);
	We suppose that this is the rectangle of the image to be
	scanned on the ImageWriter (i.e. a photo).
	What we would like to know is, which of the 8 bytes specifies
	what. Are there two bytes per rectangle corner?
	And to what offset on the printer.

2) Offset 12: resolution
	Which resolution is this. The resolution of the Thunderscan
	file image, the screen?

3) This is about the grey map and I quote:
	"The gray map consists of scan lines packed with 4 bits per
	pixel, 2 per byte, followed by remainder bytes (the fifth bit),
	8 per pixel."
	We know that there are 5 bits per pixel specifying the gray values.
	We understand that this information is grouped: two pixels in
	one byte, but what we don't understand is where EXACTLY are
	those fifth bits.
	And what is meant with: "8 per pixel". Is that 8 bits per pixel,
	or 8 bytes (the latter is suggested). If it are 8 bits per pixel
	does that mean that there are three bytes for two pixels?
	The first byte split in two, followed by one byte for pixel_1
	and one byte for pixel_2?

I hope that someone is friendly enough to help us out.
If more people are interested in these answers please e-mail me,
and I will summarize to the net.

Thanks,

               Marjo & Frank

Marjo Rottschaefer                                                    ___   
Frank Kuiper, CWI, Amsterdam.                                    _][__| |
...{decvax,philabs,seismo,okstate,garfield}!mcvax!frankk        <_______|-1
Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch.       O-O-O
-- 

               Frank
                                                                      ___   
Frank Kuiper, CWI, Amsterdam.                                    _][__| |
...{decvax,philabs,seismo,okstate,garfield}!mcvax!frankk        <_______|-1
Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch.       O-O-O