[GRASSLIST:4927] Re: read-write cells

[Glynn Clements]

Massimiliano Cannata wrote:

> When I open a new raster file (outfd=G_open_raster_new(pippo,pluto)) it 
> is open only in writing or can I also read it?

No, it's write-only.

And you can't open the file for reading until you've finished writing
it, as the map won't exist (so far as G_open_cell_old() is concerned)
until you call G_close_cell().

> Let me explane, I change my active region, the first time I applay some 
> calculations and write cell values, the next time my active region 
> overlay the old one and I want to retrive the just written data cells....
> Is it done just using:
> G_get_raster_row(outfd,outrast,row,data_type) ?????

No. If you want to read the data which you've written, you'll have to
keep a copy of it.

Also, you need to be careful about changing the region settings while
writing to a file. The region settings which were in effect at the
time you called G_open_raster_new() determine how many rows and
columns you need to write.

This is different from reading, where each call to G_get_raster_row()
etc resamples the data according to the current region settings.

-- 
Glynn Clements <glynn at gclements.plus.com>