[gdal-dev] WMS MINRESOLUTION can lead to overflow of raster dimensions

[Timothy Astle]

Thanks for the feedback Even, comments inline below.

On 23/11/2015 5:25 PM, Even Rouault wrote:
> Tim,
>
>> Would it make sense to do something as follows?  (Note:  I haven't tried
>> this yet, I'm just soliciting early feedback so please bare with me )
>>
>>
>>       if (osMinResolution.size() != 0)
>>       {
>>           double dfMinResolution = CPLAtofM(osMinResolution);
>>
>>           while (nOverviewCount > 20)
>>           {
>>               nOverviewCount --;
>>               dfMinResolution *= 2;
>>           }
>>
>>           // *** Changes here ***
>>           // Determine a suitable resolution that doesn't overflow max int.
>>           double dXSize = ((dfMaxX - dfMinX) / dfMinResolution + 0.5);
>>           double dYSize = ((dfMaxY - dfMinY) / dfMinResolution + 0.5);
>>
>>           while (dXSize > INT_MAX || dYSize > INT_MAX)
>>           {
>>               nOverviewCount --;
> I'm not sure we need to decrement the number of overviews in that loop.

Good point.

>
>>               dfMinResolution *= 2;
>>
>>               dXSize = ((dfMaxX - dfMinX) / dfMinResolution + 0.5);
>>               dYSize = ((dfMaxY - dfMinY) / dfMinResolution + 0.5);
>>           }
>>
>>           nXSize = (int) dXSize;
>>           nYSize = (int) dYSize;
>>       }
>>
>> Any thoughts?
> If that works, please open a ticket with the patch.
>
> For extra bonus, I see that a few lines below a similar overflow could also
> occur :

Sounds like a plan to me.

>
> """
>      else
>      {
>          double dfRatio = (dfMaxX - dfMinX) / (dfMaxY - dfMinY);
>          if (dfRatio > 1)
>          {
>              nXSize = nTileSize;
>              nYSize = (int) (nXSize / dfRatio);
>          }
>          else
>          {
>              nYSize = nTileSize;
>              nXSize = (int) (nYSize * dfRatio);
>          }
>
>          if (nOverviewCount < 0 || nOverviewCount > 20)
>              nOverviewCount = 20;
>
>          nXSize = nXSize * (1 << nOverviewCount);
>          nYSize = nYSize * (1 << nOverviewCount);
>      }
> """
>
> Even
>

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Tim Astle
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