[GRASS-user] Mosaic Images

[Markus Neteler]

On Tue, Mar 8, 2011 at 10:45 AM, Hamish <hamish_b at yahoo.com> wrote:
> Chethan wrote:
>> When I try to mosaic landsat images(just one band) which
>> belong to adjacent
>> path-rows they do not mosaic properly. It appears as in the
>> attached
>> screenshot. I have tried changing the order of images but
>> just the
>> overlapping image changed. I have tried r.patch as well as
>> i.image.mosaic
>> with region encompassing both the scenes. However if I
>> mosaic the same
>> images in ERDAS Imagine there are no issues. Mosaiced
>> image will be simply
>> perfect except for brightness differences. ERDAS also
>> provides options like
>> histogram matching to sort out such issues. So what is the
>> way to mosaic
>> images in GRASS? Also is there any way to use specify
>> options like
>> resampling, histogram matching in the process?
> ...
>> http://osgeo-org.1803224.n2.nabble.com/file/n6108043/mosaic.png
>
> [sorry about yahoo's linewrap]
>
>
> the d.what.rast or the query tool to check to see if the black image
> boundaries are in fact NULL, or if they are 0. If they are 0 use the
> r.null module to set them to NULL, then try again.

As an alternative, you can use r.clump2 from GRASS-Addons
and flood-fill areas (here, the "black" boundary" using the
coordinate parameter.

Markus