Plot Raster chart background

[Uwe]

I have written such a raster item for geotiff maps a couple of years ago. As far as I remember we had divided our maps into tiles ( our maps were much more, than 12000x8000, but a tile was smaller ) and the most difficult thing was to put these tiles together for each image composition.

AFAIR I had a TIFF library that offered to read the file line by line, so I didn't need to have all in memory at once. If your plot and your tiff files use the same projection all you need to do is to run over the lines in your image translate each pixel into your coordinates and pick the closest pixel from your tiff image.

Unfortunately a lot of code that does the interaction between raster data and raster item can be found in the implementation of QwtPlotSpectrogram::renderImage instead of its base class ( where it should be ). So I'm afraif you have to copy some code, that calculates the size ( = resolution ) of the image and its position in scale coordinates.

Uwe