[gdal-dev] GDAL contouring problem

[Francis Markham]

Is there any reason not to include a heuristic that uses strtod() or
similar to test for the zeroness of the last argument?

-Francis Markham

On 29 November 2010 15:24, Frank Warmerdam <warmerdam at pobox.com> wrote:
> Ole Nielsen wrote:
>>
>> I am posting this again without test files attached due the 50K size
>> limit. Anyone who wants to see them, please contact me directly.
>>
>>
>> --
>>
>> We have observed interesting anomaly with gdal_contour when one of the
>> fixed levels is zero.
>>
>> If the zero contour is expressed as 0.0 (or indeed 0.0000) gdal_contour
>> replies with the standard Usage message (see below). If the zero contour is
>> expressed as the integer 0 (or 0.00000001) it works and produces the
>> expected contours.
>
> Ole,
>
> The gdal_contour program has some rather hokey heuristics to try and
> recognise the end of the list of contour levels.  The code looks like:
>
>        else if( EQUAL(argv[i],"-fl") && i < argc-1 )
>        {
>            while( i < argc-1
>                   && nFixedLevelCount
>                             < (int)(sizeof(adfFixedLevels)/sizeof(double))
>                   && (atof(argv[i+1]) != 0 || EQUAL(argv[i+1],"0"))
>                   && !EQUAL(argv[i+1], "-3d"))
>                adfFixedLevels[nFixedLevelCount++] = atof(argv[++i]);
>        }
>
> So basically, it assumes everything is a "level" until something that
> has a numeric value of 0 is encounter that isn't the specific string
> "0".  So your analysis of the problem is essentially correct, but it is
> more or less intentional as we try to support a list of levels with no
> explicit "end of list" marker in the arguments to the command.
>
> Best regards,
> --
> ---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam,
> warmerdam at pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam
> and watch the world go round - Rush    | Geospatial Programmer for Rent
>
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