Andrea, Depending on the number of cells, dealing with > 20 raster files requires a totally different approach. Even for visualization, this is clearly a different problem than the common RGB or multi-spectral imagery. We cannot deal with 13000 raster layers in the same way as we do with a dozen.
Have you tried rasterlite? Agus El día 22 de abril de 2012 21:37, aperi2007 <aperi2...@gmail.com> escribió: > Hi Agus , > thx for your informations. > > >> Opening the raster layers very fast but getting a bad visualization >> would not be a major >> waste of time? This is what currently happens to me: the initial >> display is always useless. >> > > I understand your point of view, but i guess is not a need for every users. > Same users can't wait the 4+ minutes need for the elaboration of a raster. > Again because an user could open usually more than 20 rasters for every > session, I guess this elaboration should be absolutely optional to avoid a > really big lost of time. > > >> If your raster layers have similar statistics and or you want to >> display them with the same stretching so >> that grey levels or colors are comparable (which is often my case >> also, with time series of ndvi for example), a common style file would >> be the best solution. > > Your solution seem good to me. > > We have more set of rasters of ortophoto type colors and grey. > Eachset of colors photo is surely with comparable levels, instead I don't > know for the gray photo sets. > They are too older (1954 and so on). > > Instead for raster cell (grid data) from Lidar: > Just now we begin to merge all our sets to have a full land-cover. > So we are merging 1x1, 2x2 and 3x3 meters cells. > I don't know if this could have some trouble with having a comparable set of > values, but guess of no. > > Surely is not possible to find a unique style good for all the sets, but is > possible to establish a good style for each set. > >>...Perhaps, in > >> case a raster style is present, the by default procedure and >> calculations could be bypassed. Would this be a good solution >> in your case? >> > > You mean a file raster-style in the same folder of the raster set or of the > catalog file ? > I guess this could be a good compromise to help the use in situation like > ours. > > Andrea. > > Il 22/04/2012 19:43, Agustin Lobo ha scritto: > >> Andrea, >> >> Opening the raster layers very fast but getting a bad visualization >> would not be a major >> waste of time? This is what currently happens to me: the initial >> display is always useless. >> >> If your raster layers have similar statistics and or you want to >> display them with the same stretching so >> that grey levels or colors are comparable (which is often my case >> also, with time series of ndvi for example), a common style file would >> be the best solution. Perhaps, in >> case a raster style is present, the by default procedure and >> calculations could be bypassed. Would this be a good solution >> in your case? >> >> Agus >> >> El día 20 de abril de 2012 15:10, Andrea Peri<aperi2...@gmail.com> >> escribió: >>>> >>>> - on initial load of a raster, generate a quicklook that is the larger >>>> of 1/4 screen resolution or 500x500 pixels by sampling every nth pixel >>>> - generate a histogram from the quicklook >>>> - calculate clipped 2% - 96% range min max for each band >>>> - apply a histogram stretch based on the above >>>> - the histogram could be used for generating the graph in raster >>>> props, and the quicklook could be used to create thumbs and previews >>>> etc >>>> - ideally we should cache these quicklooks and only regenerate them if >>>> the underlying dataset has changed >>>> >>>> I believe if we do this we will have fast initial load and the images >>>> (grayscale and rgb) will 'look right' when first loaded (i.e with good >>>> contrast) and it would not be necessary to assign any color value to >>>> grayscales by default. >>>> >>>> Regards >>> >>> >>> Hi, >>> just my 2 ct. >>> >>> I guess the more important capability with raster is to open they faster >>> possible. >>> >>> I fear calculate all these values on first opened take more time than >>> what >>> is waitable for the open of a raster. >>> >>> Perhaps this action should be choosable by settings ? >>> >>> Of course I see our situation. >>> >>> Our situation is of more sets of raster (7-800 each set) where every >>> raster >>> is grey level or true color of 3-400 Mbyte each. >>> And all these raster are accessible by a remote shared server to our >>> users. >>> For a total, actually, of about 13.000 rasters. >>> >>> I don't understand if this new feature could be really usable in a >>> situation >>> like our. >>> >>> -- >>> ----------------- >>> Andrea Peri >>> . . . . . . . . . >>> qwerty àèìòù >>> ----------------- >>> >>> >>> _______________________________________________ >>> Qgis-developer mailing list >>> Qgis-developer@lists.osgeo.org >>> http://lists.osgeo.org/mailman/listinfo/qgis-developer >>> >> > _______________________________________________ Qgis-developer mailing list Qgis-developer@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-developer