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<DIV><FONT face=Arial size=2><SPAN
class=530224720-02022007>Hi,</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=530224720-02022007></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=530224720-02022007>I am working with
panchromatic satellite imagery, which has the typical "black borders" around the
image area.</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=530224720-02022007></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=530224720-02022007>When using gdalwarp
to reproject the imagery, I specifiy scrnodata and dstnodata as 0, in order to
make 0 look "transparent" in my image viewer. This works fine. I also make sure
that within my image area, no black pixels occur, for visual purposes (i.e.
each pixel within the image area has a digital number of at least
1).</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=530224720-02022007></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=530224720-02022007>The problem that I
am encountering is that cubic convolution allows pixel values - within the
imagery area - to become black (digital number 0), because of the formula of
cubic convolution.</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=530224720-02022007></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=530224720-02022007>This gives me
problems, because when I then make 0 look transparent, it appears as if I have
holes in my image area.</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=530224720-02022007></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=530224720-02022007>Would it make sense
to not allow gdalwarp to change the pixel value from something larger than 0 to
0, if the user specifies dstnodata as 0? Is this currently possible with
gdalwarp?</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV align=left>
<DIV><FONT face=Arial size=2><SPAN class=530224720-02022007>Thanks for your
help!</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Yours truly,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Wim Chalmet<BR></FONT></DIV></DIV></BODY></HTML>