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<body class='hmmessage'><div dir='ltr'>Hi Even,<br><br><div>> From: even.rouault@mines-paris.org<br>> To: gdal-dev@lists.osgeo.org<br>> Subject: Re: [gdal-dev] Default GeoTransform for MEM driver<br>> Date: Mon, 9 Dec 2013 20:54:35 +0100<br>> CC: lucena_ivan@hotmail.com; tkeitt@utexas.edu; jukka.rahkonen@mmmtike.fi<br>> <br>> Le lundi 09 décembre 2013 18:08:19, Ivan Lucena a écrit :<br>> > The other problem with that documentation is the return code. CE_Failue<br>> > means that the driver does not support it and/or that the dataset doesn't<br>> > have it.<br>> <br>> The current behaviour of the MEM driver doesn't particularly shock me. It <br>> seems OK to return CE_Failure if SetGeoTransform() hasn't been explicitely <br>> called to define it. And as far as the default geotransform, it is a matter of <br>> taste. [ 0, 1, 0, 0, 0, 1] would be indeed a bit more classical for a <br>> ungeoreferenced image, but one can consider that if GetGeoTransform() returns <br>> CE_Failure, the returned geotransform is to be ignored.<br><br>That is good to know. So it really doesn't matter if the driver support geotransformation or not.<br><br>But my concern is when it returns CE_None. What does it really means because I was checking some driver's implementation of GetGeoTransform and I noticed that some of then always return CE_None no matter what. So would that be possible that a dataset is *ungeoreferenced* and a driver returns CE_None with the default values [0, 1, 0, 0, 0, 1]. Should we trust that those values [0, 1, 0, 0, 0, 1] are correct or are they just a default filler?<br><br>For example, to get [0, 1, 0, 0, 0, 1] we should expect a world-file that should be something like:<br><br>1.0000000000<br>0.0000000000<br>0.0000000000<br>1.0000000000<br>0.5000000000<br>0.5000000000<br><br>Not:<br><br>1.0000000000<br>0.0000000000<br>0.0000000000<br>1.0000000000<br>0.0000000000<br>0.0000000000<br><br>Anyway, I will trust that the CE_None means that the geotransformation values are correct but should I will also check if the values are equal to [0, 1, 0, 0, 0, 1] just in case? And what to do if they are?<br><br>Sorry to introduce a question that is not exactly related to the topic, the MEM driver.<br><br>Regards,<br><br>Ivan<br><br>> <br>> To answere Tim's initial question {0, 1, 0, 0, 0, -1} is a north-up image : <br>> (0,0) is the coordinate of the upper left of the top left pixel, and y values <br>> are decreasing with image rows.<br>> <br>> Even<br>> <br>> -- <br>> Geospatial professional services<br>> http://even.rouault.free.fr/services.html<br></div> </div></body>
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