[gdal-dev] Splitting and projecting a large .sid image

[Stephen Woodbridge]

Hi all,

This is my annual wake-up got to do something with rasters and forgot 
the finer details of the last time I did a problem similar to it.

I have a bunch of LandSat mrsid imagery, they are in multiple UTM zone 
projections and I want to convert them to geographic projection, WGS84, 
and into tiff files. The files are too large to convert into a single 
tif, so I plan to quarter each file into 4 pieces.

So I wrote a script the reads the files and collects info about them, 
then generates 4 gdalwarp commands to reproject each quarter of the file 
(perl included below). A typical command looks like:

gdalwarp -srcnodata 0 -dstnodata 0 -s_srs +init=epsg:32642 -t_srs 
EPSG:4326 -te 68.9999676729652 24.9707453133203 72.7715338115736 
27.4799559407707 -rb -wm 250 --config GDAL_ONE_BIG_READ ON -co 
"TILED=YES" ./GeoCover2000/n-42-25.sid ./af/n-42-25_1-0.tif


The reprojection seems to have worked fine, but the bounds seem to be 
off because of the black (nodata) areas.

You can see my poor results here:
http://imaptools.com/downloads/raster.gif

Is there a better way to do this? I seem to remember a tool to generate 
tiles.
Does this need to be done in two steps? How?
Did I mess up my logic below? I've been over it multiple times and do 
not see any errors.

Any help would be appreciated.

Thanks,
   -Steve

$ gdalinfo -nomd ./GeoCover2000/n-42-25.sid
Driver: MrSID/Multi-resolution Seamless Image Database (MrSID)
Files: ./GeoCover2000/n-42-25.sid
Size is 51078, 39090
Coordinate System is `'
Origin = (136066.125000000000000,3323577.375000000000000)
Pixel Size = (14.250000000000000,-14.250000000000000)
Corner Coordinates:
Upper Left  (  136066.125, 3323577.375)
Lower Left  (  136066.125, 2766544.875)
Upper Right (  863927.625, 3323577.375)
Lower Right (  863927.625, 2766544.875)
Center      (  499996.875, 3045061.125)
Band 1 Block=1024x128 Type=Byte, ColorInterp=Red
   Minimum=0.000, Maximum=226.000, Mean=109.610, StdDev=39.202
   Overviews: 25539x19545, 12770x9773, 6385x4887, 3193x2444, 1597x1222, 
799x611, 400x306, 200x153
Band 2 Block=1024x128 Type=Byte, ColorInterp=Green
   Minimum=0.000, Maximum=229.000, Mean=125.833, StdDev=31.828
   Overviews: 25539x19545, 12770x9773, 6385x4887, 3193x2444, 1597x1222, 
799x611, 400x306, 200x153
Band 3 Block=1024x128 Type=Byte, ColorInterp=Blue
   Minimum=0.000, Maximum=227.000, Mean=107.092, StdDev=37.230
   Overviews: 25539x19545, 12770x9773, 6385x4887, 3193x2444, 1597x1222, 
799x611, 400x306, 200x153


$ cat ./GeoCover2000/n-42-25.prj
Projection     UTM
Datum          WGS84
Zunits         NO
Units          METERS
Zone           42
Xshift         0.000000
Yshift         0.000000
Parameters



Perl snippet:

     foreach my $sid (@files) {

         next unless $wanted && $sid =~ /$wanted/i;

         if (! -r $sid) {
             warn "SKIPPING: $sid is not readable!\n";
             next;
         }

         my $gdalinfo = `gdalinfo -nomd $sid`;

         # parse out the strings that we need

         $gdalinfo =~ /Upper Left  \((\s*[^,]+),\s*([^\)]+)/s || warn 
"Upper Left parse error\n";
         my $ul = [$1, $2];
         $gdalinfo =~ /Lower Left  \((\s*[^,]+),\s*([^\)]+)/s || warn 
"Lower Left parse error\n";
         my $ll = [$1, $2];
         $gdalinfo =~ /Upper Right \((\s*[^,]+),\s*([^\)]+)/s || warn 
"Upper Right error\n";
         my $ur = [$1, $2];
         $gdalinfo =~ /Lower Right \((\s*[^,]+),\s*([^\)]+)/s || warn 
"Lower Right error\n";
         my $lr = [$1, $2];

         my $outf = $sid;
         $outf =~ s/\.sid//;
         $outf =~ m/\/([^\/]+)$/;
         $outf = $1;

         my $prj = $sid;
         $prj =~ s/\.sid/.prj/;
         if (! -r $prj) {
             warn "SKIPPING: $prj is not readable!\n";
             next;
         }
         my $projinfo = `grep Zone $prj`;
         if ($projinfo =~ /^Zone\s*([-+]?\d+)/) {
             my $znum = $1;
             if ($znum < 0) {
                 $epsg = 32700 - $znum;
             } else {
                 $epsg = 32600 + $znum;
             }
         }
         else {
             warn "SKIPPING:  could not find zone or epsg in $prj\n";
             next;
         }

         my $proj = sprintf("+init=epsg:%d", $epsg);
         print "Using projection: $proj for $projinfo" if $DEBUG;

         my $pj = Geo::Proj4->new($proj);
         if (! $pj) {
             warn "SKIPPING: Geo::Proj4 error: " . Geo::Proj4->error . "\n";
             next;
         }

         $ul = [reverse $pj->inverse(@$ul)];
         $ll = [reverse $pj->inverse(@$ll)];
         $ur = [reverse $pj->inverse(@$ur)];
         $lr = [reverse $pj->inverse(@$lr)];

         # this is probably a parallelgram in latlong
         if ($DEBUG) {
             printf("ul = %11.6f, %11.6f\n", @$ul);
             printf("ll = %11.6f, %11.6f\n", @$ll);
             printf("ur = %11.6f, %11.6f\n", @$ur);
             printf("lr = %11.6f, %11.6f\n", @$lr);
         }

         # Get the bbox of the parallelgram
         my $xmin = $ul->[0]<$ll->[0]?$ul->[0]:$ll->[0];
         my $xmax = $ur->[0]>$lr->[0]?$ur->[0]:$lr->[0];
         my $ymin = $ll->[1]<$lr->[1]?$ll->[1]:$lr->[1];
         my $ymax = $ul->[1]>$ur->[1]?$ul->[1]:$ur->[1];

         my $tiled = '-co "TILED=YES"';
         $tiled = '' if -e $outf;

         my $nparts = 2;
         my $dx = ($xmax - $xmin) / $nparts;
         my $dy = ($ymax - $ymin) / $nparts;
         my ($x0, $x1, $y0, $y1);
         for (my $i=0, $x0=$xmin; $i<$nparts; $i++, $x0 += $dx) {
             $x1 = $x0 + $dx;
             for (my $j=0, $y0=$ymin; $j<$nparts; $j++, $y0 += $dy) {
                 $y1 = $y0 + $dy;
                 my $tif = sprintf("%s/%s/%s_%d-%d.tif", $work, $outd, 
$outf, $i, $j);
                 my $cmd = sprintf("gdalwarp -srcnodata 0 -dstnodata 0 
-s_srs +init=epsg:%d -t_srs EPSG:4326 -te $x0 $y0 $x1 $y1 -rb -wm 250 
--config GDAL_ONE_BIG_READ ON $tiled $sid $tif\n", $epsg);

                 print "$cmd\n";
                 my $rc = system($cmd);
                 print "SYSTEM returned: " . sprintf("%lx\n", ($rc & 
0xffff))
                     if $DEBUG
             }
         }
     }