[Gdal-dev] [newbie] Reading of large TIF files

[t.laue at web.de]

Dear all,

I am currently developing a small application using Qt 4 and C++ for handling and 
evaluating large aerial images given in TIF / TIFF format. I am using GDAL for image 
input. I am working with image overviews and image tiles for providing a good zoom 
and pan performance. 

At the moment GDALRasterBand::RasterIO is being used for accessing overview levels 
and reading small image patchs because I did not find a way how to read from single 
overview levels using GDALDataset::RasterIO. Everything is working fine as long as I 
am utilising gray value images with one raster band.

In the case of RGB images I can employ a loop for retrieving the data of all three raster 
bands from the same overview level resulting in three buffers which contain the data. I 
would like to display the color image at the screen but I have no idea how to combine 
them again.

Is there a way to create a new dataset for adding the data read from different bands? Is 
it possible to use GDALDataset to access single overview levels? Do I have to use 
another method independent of GDAL to bring the three buffers together in order to 
recreate a RGB image patch? Is anyone working with Qt 4 and GDAL? 

I am very thankful for every hint and idea.

Best regards

Thomas