[gdal-dev] Can I change SOURCE_EXTRA setting at compile time?

[Roger André]

Hi Frank,

You're absolutely right.  Changing those values in mapresample.c to 10
removed the artifacts when using a WMS request.  They're still present when
the request is made via mapscript though.  I need to manually code a
mapscript example though, because right now I'm testing that via TileCache,
and I'm not 100% certain how the image is being requested.  Can you think of
a reason why WMS would be different from a straight read and reproject
through mapscript?

cc'ing TileCache list and mapserver lists as well
--

On Tue, Nov 18, 2008 at 5:58 PM, Frank Warmerdam <warmerdam at pobox.com>wrote:

> Roger André wrote:
>
>> Hi Frank,
>>
>> I've theorized all sorts of reasons for what I'm seeing.  So far none of
>> them are right.  Basically, if I take a really high-res epsg:4326 image, and
>> serve it up through Mapserver in epsg:900913, there are instances where I
>> get images back which are missing rows of pixels at the bottom of the image.
>>  If I reduce the resolution of the image the lines go away.  I haven't yet
>> figured out at what resolution the problem starts to appear.
>>
>> I just tested the idea of changing the values in the warper code:
>> First:
>> nResWinSize += 100;
>> Then:
>> nResWinSize += 500;
>>
>> Then rebuilt gdal.   Didn't seem to make a difference.
>>
>
> Roger,
>
> Are you sure the GDAL warper is being used? If the reprojection is being
> done by MapServer it will be using the MapServer warper.
>
> Try changing the +- 1.0 values to larger values in the following code in
> mapserver's mapresample.c:
>
> /* -------------------------------------------------------------------- */
> /*      Project desired extents out by 2 pixels, and then strip to      */
> /*      available data.                                                 */
> /* -------------------------------------------------------------------- */
>    memcpy( &sOrigSrcExtent, &sSrcExtent, sizeof(sSrcExtent) );
>
>    sSrcExtent.minx = floor(sSrcExtent.minx-1.0);
>    sSrcExtent.maxx = ceil (sSrcExtent.maxx+1.0);
>    sSrcExtent.miny = floor(sSrcExtent.miny-1.0);
>    sSrcExtent.maxy = ceil (sSrcExtent.maxy+1.0);
>
>
> See if that helps.  Currently there is no processing option that does
> what SOURCE_EXTRA does, though it might be worth adding one.
>
>
> 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<http://pobox.com/%7Ewarmerdam>
> and watch the world go round - Rush    | Geospatial Programmer for Rent
>
>
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