AWARE SYSTEMS
TIFF and LibTiff Mail List Archive

Thread

1999.09.10 14:45 ".tfw format", by Mario Boratto
1999.09.11 06:01 "Re: .tfw format", by James McMullen
1999.09.13 15:22 "RE: .tfw format", by Geoff Vandegrift

1999.09.13 15:22 "RE: .tfw format", by Geoff Vandegrift

Title: RE: .tfw format

TFW has been a thorn in my side for quite some time. All of our users expect support for TFW; but until recently, the only "specification" we had for the format was in legacy source code.

From two different sources (ArcView help files and a contact at ESRI) I have recently been informed that the items in the TFW file are actually supposed to be the non-trivial elements from a 2D, affine transformation matrix:

/ A B C \
| D E F |
\ 0 0 1 /

Using the symbols above, the TFW file is organized as follows:

A
D
B
E
C
F

I have yet to see a sample tfw file where the B and D terms are non-zero (indicating rotation). In fact, the ArcView help files say that rotation is not supported.

It turns out that our interpretation (i.e., the legacy code) of rotation has been wrong all along, but we were okay because no one seems to ever use rotation in tfw.

If anyone has anything to add to this, I would be extremely interested.

Geoff Vandegrift
Senior Software Developer

Hitachi Software Global Technology, Ltd.

> -----Original Message-----
> From: James McMullen [mailto:james@iiMap.com]
> Sent: Saturday, September 11, 1999 12:01 AM
> To: Mario Boratto; tiff@olympiakos.com
> Subject: Re: .tfw format