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<DIV>Hi Jason</DIV>
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<DIV>Well, ECW use wavelet compression, which is lossy, and data values can get changed slightly.</DIV>
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<DIV>regards,</DIV>
<DIV><BR>Robert<BR><BR>>>> Jason Beverage <jasonbeverage@gmail.com> 16/03/2010 10:27 a.m. >>><BR>Hey again,<BR><BR>Some more information, the file I was using was an ECW I converted from a tif. The black splotches appear if I use the ECW, but if I use the original tif file I don't see them.<BR><BR>However, when using AVERAGE or BILINEAR, it appears as if the alpha values are either completely transparent or completely opaque. The image I'm using is an image I used the gdalwarp -cblend option on to do some polygon cutting so I'm losing my blending line if I do average or bilinear resampling. I'll see if I can create a small example that shows the issue.<BR><BR>Thanks,<BR><BR>Jason<BR><BR></DIV>
<DIV class=gmail_quote>On Mon, Mar 15, 2010 at 3:55 PM, Robert Sanson <DEFANGHTML_SPAN dir=ltr><<A href="mailto:SansonR@asurequality.com">SansonR@asurequality.com</A>></DEFANGHTML_SPAN> wrote:<BR>
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<DIV>Hi Jason</DIV>
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<DIV>That's not unexpected. RESAMPLE=NEAREST preserves the "nodata" vales used in the mask. BILINEAR or AVERAGE combine values from adjoining pixels, so the "nodata" pixels get some other value.</DIV>
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<DIV>regards,</DIV>
<DIV><BR>Robert<BR><BR>>>> Jason Beverage <<A href="mailto:jasonbeverage@gmail.com" target=_blank>jasonbeverage@gmail.com</A>> 16/03/2010 4:53 a.m. >>>
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<DIV class=h5><BR>Hi all,<BR><BR>I have some imagery that is in UTM that contains an alpha band that<BR>masks out areas with no data. When I use MapServer to reproject it to<BR>epsg:4326, the masked out area looks good if I set RESAMPLE=NEAREST on<BR>the layer. If I change the RESAMPLE option to BILINEAR or AVERAGE I<BR>get black splotches in the area that is transparent.<BR><BR>Has anyone else seen this behavior?<BR><BR>I'm using MapServer 5.6.1<BR><BR>Thanks,<BR><BR>Jason<BR></DIV></DIV>_______________________________________________<BR>mapserver-users mailing list<BR><A href="mailto:mapserver-users@lists.osgeo.org" target=_blank>mapserver-users@lists.osgeo.org</A><BR><A href="http://lists.osgeo.org/mailman/listinfo/mapserver" target=_blank>http://lists.osgeo.org/mailman/listinfo/mapserver</A>-users<BR><BR></DIV><BR><BR>
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