[Qgis-developer] Integrating OSSIM with QGIS

[Radim Blazek]

On Wed, Jun 8, 2011 at 9:21 PM, Mingjie Su <Su.Ming at geoeye.com> wrote:
> All-
>   We are making some good progress on the ossim image provider (qgsossimprovider.cpp). Couple questions:
>
> (1) Is there a way for users to specify which provider to use? It looks like QGIS is hard coded to use the GDAL provider.

I would like to implement drag-and-drop from QBrowser to QGIS soon.
Then if you implement dataItem() in your provider, it will be possible
to drag your layers directly from file tree in the QBrowser.

> (3) Black pixels (0,0,0 RGB) are being flipped to transparent. Is there a way to override this behavior programatically?

You should be able to set 'no data' reimplementing
isNoDataValueValid() and noDataValue(). I am not sure however if it
works with 3-bands rasters correctly. Note that it is also possible to
represent a raster as image using ARGBDataType which is probably also
faster then 3-bands because it does not have to read data 3 times.
Then however, the access to true data is lost and it is impossible to
switch bands etc.

We should probably add another data type similar to ARGBDataType,
something like ThreeBands or Byte3 which would allow to read 3 bands
in one call. The GDAL provider would also benefit from this.

> (4) In OSSIM we have a concept of image chains and connectable objects. You can wire up all kinds of filters and equations into a workflow to create an output image. The image chain can be represented using an array of key value pairs. Does the provider interface provide a mechanism for passing this type of information?

The concept of chains should be included in
https://github.com/polymeris/qgis/wiki/QGIS-Processing-Framework in my
opinion. So that chains can be created using data and tools from
various providers and packages.  Or at least, the framework should be
designed so, that it will allow later addition of chains on some upper
level.

Radim