[gdal-dev] Histograms without null pixels
Chaitanya kumar CH
chaitanya.ch at gmail.com
Mon Mar 4 21:49:27 PST 2013
gdalinfo uses the GetDefaultHistogram() method which can do this faster by
fetching a precomputed histogram.
gdalinfo is a command line program. Even a default histogram of 256 buckets
is hard to visualize in text mode. A much better way is to use a desktop
GIS like qgis to view the histogram.
Can you justify adding this extra functionality in gdalinfo?
On Tue, Mar 5, 2013 at 10:56 AM, Caleb Hanger <cdhanger at gmail.com> wrote:
> I am writing a script which is calling gdalinfo to get a histogram of
> pixel values in an image file. Apparently the mechanism for obtaining a
> "default" histogram enables the "bIncludeOutOfRange" flag to dump
> not-in-range pixels (including null pixels, in formats that support it)
> into whichever bin of the histogram is closest. I see that in the
> GetHistogram() function, the functionality is already coded to respond
> appropriately to either a true *or* false value in this flag. However, I
> can't seem to find any way to turn that flag off through any of the
> user-level programs (in particular, gdalinfo), rendering the parameter to
> the function useless, unless I'm just not looking hard enough. Hence, my
> 1) Is there any standard user-level operation (preferably in gdalinfo)
> which disables, or at least *allows* for disabling of, the
> bIncludeOutOfRange flag? If so, I can't find it.
> 2) If not, how come? Has there been no apparent need for histograms that
> omit null values or other "out of range" situations?
> Thanks in advance for any insight,
> Caleb Hanger
> gdal-dev mailing list
> gdal-dev at lists.osgeo.org
Chaitanya kumar CH.
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