Unclear display in mapviewer

Question

Can someone help me with this:
I imported a tiff file as a blob in the georaster table, and can show it with mapviewer. But the image is in fact 12000 x 7500 pixels. Map is 8000 x 5000 m. While in mapviewer it can only be shown in maximum 933 x 583
In that case I tell mapviewer to show me the map on differnet sizes, with a width=933 and a height=583.
Size 500 gives me a very precise and clear image.
But when I ask for example size 1500 or higher, so I zoom out, the lines are interrupted more and more, and the labels on the map are harder or impossible to read.
What is the cause of this problem?
I tried the different possibilities of resampling attributes in the generate_pyramid parameters, and that didn't seem to resolve the problem.
Is it possible that I MUST do the sdo_geor.change_format?
Until now I left the change_format away, because I couldn't give the bands in the blocksize attribute.
Without the bands, I have a color image, while if I use bands, I get a grayscale image.
Did anyone have the same problem when importing TIF files as BLOBs in a georaster table, and showing them in Mapviewer?
PS: I use Oracle 10g.

Answer 1

Hi Catherine,
you don't need to use the sdo_geor.change_format for MapViewer. You use this procedure in case you want to change your current GeoRaster data format.
What is important for MapViewer, is to have your GeoRaster georeferenced and also have the spatial extent for the georaster column updated and indexed.
It is also recommended that you build pyramid levels. In the case where you don't specify the pyramid level on your request, MapViewer will choose the best level based on your query window and device window. With pyramid levels, you will have different levels of representation for your GeoRaster, varying from a more detailed to a less detailed representation.
So when you zoom out (increase the map size), MapViewer may get a less detailed representation of your map, unless you specify on your map request the pyramid level that you want. If you built pyramid levels for your GeoRaster, and assuming that the image has lines and labels, the lines and labels on your lower level representations may not be well defined.
Joao