[QGIS-trac] Re: [Quantum GIS] #857: Option to ignore transparency values in "Load Min Max From Band" button

[Quantum GIS]

#857: Option to ignore transparency values in "Load Min Max From Band" button
-----------------------------------------------------+----------------------
        Reporter:  cgs_bob                           |         Owner:  ersts        
            Type:  defect                            |        Status:  closed       
        Priority:  major: does not work as expected  |     Milestone:  Version 1.0.0
       Component:  Rasters                           |       Version:  HEAD         
      Resolution:  fixed                             |      Keywords:               
Platform_version:                                    |      Platform:  Gentoo       
        Must_fix:  No                                |   Status_info:  0            
-----------------------------------------------------+----------------------
Changes (by ersts):

  * status:  new => closed
  * resolution:  => fixed

Comment:

 The NoDataValue is now excluded in both the estimated and internally
 computed min-max.

 As for the second idea, after some thought I don't think excluding 100%
 transparent values will be possible or really appropriate.

 1) The raster class is currently heavily reliant on GDAL, and uses GDAL's
 GDALComputeRasterMinMax to get the estimated min-max values. This function
 does not have the ability to ignore values other then the nodatavalue - as
 far as I understand

 2) The transparency setting is just that, a way to change the transparency
 of pixel values. It is not really an on the fly recoding capability. I
 think a simple raster reclassify plugin would be the way to go, which
 could be a great core feature as well but not something that will be
 possible for v1.0

 This idea should be revisited toward v2.0

-- 
Ticket URL: <http://trac.osgeo.org/qgis/ticket/857#comment:2>
Quantum GIS <http://qgis.org>
Quantum GIS is an Open Source GIS viewer/editor supporting OGR, PostGIS, and GRASS formats