MrSID mapserver vs gdal_translate

[Simpson]

Hi,

I find gdal_translate about three times faster than mapserver when
processing a small area from a MrSID file.  If I add a class definition to
the layer in the map file, the results are black and white, but the image
renders at about the same speed as gdal_translate.  Is this disparity in
time a result of bands being extracted separately?

Thanks for any help,
Drew.


GDAL_TRANSLATE RUN
    # time gdal_translate -of png -outsize 600 600 -projwin 237197.849522
3385281 >
    Input file size is 47637, 39167
    Computed -srcwin 5376 34431 1251 1252 from projected window.
       20.05s real    17.87s user     2.15s system

MAPSCRIPT RUN
    # time ./ms_mrsid.cgi
    Generating map...
    [Fri Sep 10 09:14:12 2004].218670 msDrawRasterLayerLow(dynraster):
entering.
    [Fri Sep 10 09:14:12 2004].225859 msDrawGDAL(): red,green,blue,alpha
bands = 1,2,3,0
    Map done.  Output in ./1094825652.mp.png
       65.13s real    58.31s user     6.28s system

MAPSERVER VERSION
    MapServer version 4.0.1 OUTPUT=PNG OUTPUT=JPEG OUTPUT=WBMP
    SUPPORTS=PROJ SUPPORTS=FREETYPE
    SUPPORTS=WMS_SERVER SUPPORTS=WMS_CLIENT
    SUPPORTS=WFS_SERVER SUPPORTS=WFS_CLIENT INPUT=TIFF
    INPUT=EPPL7 INPUT=JPEG INPUT=POSTGIS
    INPUT=OGR INPUT=GDAL INPUT=SHAPEFILE

GDAL_VERSION
    1.2.1

OS
    Linux xxx 2.4.20-28.8 #1 Thu Dec 18 12:53:39 EST 2003 i686 i686 i386
GNU/Linux

IMAGERY

        Landsat data from https://zulu.ssc.nasa.gov/mrsid/
        Specifically
https://zulu.ssc.nasa.gov/mrsid/bin/download_file.pl?client=etmpsmos/sid&ima
ge=N-16-30_2000.tar  (may take multiple attempts to download)

MAP FILE

    NAME DEMO
    STATUS ON
    SIZE 600 600
    EXTENT 237197.849522 3367440.634804 255029.015690 3385281.561774
    UNITS meters
    SHAPEPATH "data"
    IMAGECOLOR 255 255 255
    DEBUG ON
    IMAGETYPE png_rgb

    OUTPUTFORMAT
      NAME png_rgb
      DRIVER "GD/PNG"
      MIMETYPE "image/png"
      IMAGEMODE RGB
      EXTENSION "png"
    END

    WEB
      IMAGEPATH "set in demo_init.html"
      IMAGEURL "set in demo_init.html"
      LOG "/home/asimpson/wms/mapserver.log"
    END

    LAYER
      NAME dynraster
      TYPE RASTER
      MAXSCALE 6000000000
      STATUS DEFAULT
      DEBUG ON
      DATA "/home/asimpson/wms/data/n_16_30_2000c.zu.sid"
      #CLASS
      #  NAME "dynraster"
      #END
    END

    END # Map File

MAPSCRIPT

    #!/usr/bin/perl

    use strict;
    use mapscript;

    $| = 1;

    my $time        = time;
    my $tmp_base    = $time;
    my $scratch     = "./";
    my $mapfile     = "./ms_mrsid.map";

    GenerateMap();

    exit;

    #################################################
    sub GenerateMap
    {
        my($map,$img,$map_file,$layer);
        my($numlayers,$l);

        print "Generating map...\n";

        $ENV{MS_ERRORFILE} = './mapserver.log';

        $map = new mapscript::mapObj($mapfile) || die
$mapscript::ms_error->{code}.": ".$mapscript::ms_error->{message};

        $img = $map->draw() or die "Unable to render
map.".$mapscript::ms_error->{message};

        $map_file    = "$time.mp.png";

        $img->save($scratch.$map_file);

        print "Map done.  Output in $scratch$map_file\n";
    }