This procedure would not work well for thematic maps (qualitative variable) but I think it is reasonable as initial default. Nevertheles, a qualitative scheme should be ready for thematic maps (i.e. landcover, vegetation or soil maps). Maybe the 12 classes color table from colorbrewer could be a good first option: http://colorbrewer2.org/index.php?type=qualitative&scheme=Set3&n=12
Also, median should be used instead of mean and mad instead of sd to calculate the clipping (at least optionally) as raster layers do have outliers: mad is just the median of the absolute value of the differences to the median: median(abs(x-median(x)) Agus El día 20 de abril de 2012 14:46, Tim Sutton <[email protected]> escribió: > Hi > > On Fri, Apr 20, 2012 at 2:17 PM, Marco Hugentobler > <[email protected]> wrote: >> Hi >> >> >>>BTW Freak out will go after resampler branch is merged.... >> >> I've managed to convert freakout style to singleband pseudocolor in the >> project file / qml conversion to the new format :-) >> >>> - visualizing monoband rasters could be improved: >>> >>> - why not loading it with a greyscale by default? or with a colour ramp? >>> - why not adding a dtm colour table (we can take the one >> >> >> I'd like to improve selecting colorramps in the raster resampler branch >> (that would even allow us to add a freakout color ramp for trips down memory >> lane). >> >> Default style: I'm not sure what would be a good default, since we don't >> know the value range at the beginning (at least not without doing a time >> consuming value scan). Do you have any ideas (maybe a partial raster scan to >> speed things up?). >> > > Yes - Julien had a really nice suggestion to implement the following logic: > > - 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 > > Tim > > >> Regards, >> Marco >> >> >> On 20.04.2012 11:10, Tim Sutton wrote: >>> >>> Hi >>> >>> On Fri, Apr 20, 2012 at 10:47 AM, Giovanni Manghi >>> <[email protected]> wrote: >>>> >>>> On Fri, 2012-04-20 at 10:19 +0200, Paolo Cavallini wrote: >>>>> >>>>> Hi all. >>>>> Visualizing monoband rasters could be improved: >>>>> - why not loading it with a greyscale by default? or with a colour ramp? >>>>> - why not adding a dtm colour table (we can take the one >>>>> in/usr/lib/grass64/etc/colors/terrain), possibly replacing the Freak out >>>>> one? >>>> >>>> +100 >>>> much needed improvements >>>> >>> All good ideas but we are feature frozen so lets first focus on >>> releasing 1.8 and then we can do these. >>> >>> BTW Freak out will go after resampler branch is merged.... >>> >>> Regards >>> >>> Tim >>> >>>> -- Giovanni -- >>>> >>>> >>>> >>>> _______________________________________________ >>>> Qgis-developer mailing list >>>> [email protected] >>>> http://lists.osgeo.org/mailman/listinfo/qgis-developer >>> >>> >>> >> >> >> -- >> Dr. Marco Hugentobler >> Sourcepole - Linux& Open Source Solutions >> Churerstrasse 22, CH-8808 Pfäffikon SZ, Switzerland >> [email protected] http://www.sourcepole.ch >> Technical Advisor QGIS Project Steering Committee >> >> >> _______________________________________________ >> Qgis-developer mailing list >> [email protected] >> http://lists.osgeo.org/mailman/listinfo/qgis-developer > > > > -- > Tim Sutton - QGIS Project Steering Committee Member (Release Manager) > ============================================== > Please do not email me off-list with technical > support questions. Using the lists will gain > more exposure for your issues and the knowledge > surrounding your issue will be shared with all. > > Visit http://linfiniti.com to find out about: > * QGIS programming and support services > * Mapserver and PostGIS based hosting plans > * FOSS Consulting Services > Skype: timlinux > Irc: timlinux on #qgis at freenode.net > ============================================== > _______________________________________________ > Qgis-developer mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/qgis-developer _______________________________________________ Qgis-developer mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/qgis-developer
