TIF files, r.tiff, pbmplus

[Bart Cosyn]

Hi all,

On Wed, 18 Jan 1995, DUNN JEREMY SIMON wrote:

> 
> Hello, 
> 
> Does anyone have any experiece with importing .TIF files into Grass4.1 ? 
> 

Yes I got and it works but it takes some time. In fact i was also trying 
to compile r.tiff from SCS (src.contrib) but it failed because he could 
not find something like a sun library. I tried it on a silicon but failed.

There are some options for doing it in an other way:

1) We have a tool here called "convert" of ImageMagick 3.4. I do not know 
where it comes from but it works. There you can convert a tiff file to 
one big raw file containing the 3 colorbands of a coloured image. As they 
are putted in one file you need to divide the file in exactly three parts 
and import the binaries in Grass. After you recompose the file to an rgb 
file by using i.composite.

2) A friend of mine (Andrea Giacomelli) has another method using pbmplus 
(in src.related) 
and xv and it works also. I did it the same way and gives good results. 
Here is the long procedure f.i you got a file called test.tif. Do this:

	tifftopnm test.tif > test
	ppmtorgb3 test (this creates 3 colorbands with the names test.red 
.blu and .grn)
	
These 3 files are not really the raw files. Now you need to use xv to see 
some things.
	xv test.red

In xv you can do an textview of the file. You will see a header
in ascii like :
	
	P5
	2048 2048
	255

It means you got a file of 2048 lines and columns with 255 colors. No 
idea what P5 means. As I know the number of lines and col. and as it is 
only 255 colors this image must contain 2048*2048*1=4194304 bytes. But 
you will see that your file is 4194321 bytes long. So the header is 17 
bytes bigger. I delete these 17 byte using the following.

dd if=test.blu of=raw.blu ibs=17 skip=1

Probably there is a better way but as sometimes tail and head have a 
limit of lines and as i am not that good with line editing, this looks 
the best thing to do. The idea of this dd is. I read test.blu in blocks 
of 17 bytes and copy it to raw.blu but by skipping the first 17 byte i 
skip the header and only retain the raw array! 

Now go to grass and import your file in Grass as a binary array. Or 
better run r.support after putting your file in the cell direct.!

do this  for all the colorbands or  put it in a script!

Than use i.composite to restore the rgb file. I you never worked with it 
read also i.group!

Hope it helps but if there is another and more comfortable way to do it 
please let me know!

			Bart and Andrea



**************************************************************************

	ir. Bart Cosyn
	EC- Environment project
	CRS4
	Environmental modelling group
	Via Nazario Sauro, 10
	09123-Cagliari
	Italy
	Tel +/39/70/2796278
	Fax +/39/70/2796216
	E-mail: bcosyn at crs4.it
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