mapserver displays raster image in mirror

Question

I've installed Mapserver and used a map file to set a raster layer and vector(shp) layers on top of it. However, although displayed in the expected order, the png file is displayed in mirror(compared to it while being built in OpenEV):

any ideas on what is the cause of this and a possible remedy are welcomed. Thanks!

from the .map file, the raster layer:

  LAYER
    NAME "level_2"
    TYPE RASTER
    STATUS DEFAULT
    DATA "lv2.png"
  END

gdalinfo on the .png file

Driver: PNG/Portable Network Graphics
Files: /var/www/mapsdemo/e/data/lv2.png
Size is 1591, 967
Coordinate System is `'
Metadata:
  Software=gnome-screenshot
Image Structure Metadata:
  INTERLEAVE=PIXEL
Corner Coordinates:
Upper Left  (    0.0,    0.0)
Lower Left  (    0.0,  967.0)
Upper Right ( 1591.0,    0.0)
Lower Right ( 1591.0,  967.0)
Center      (  795.5,  483.5)
Band 1 Block=1591x1 Type=Byte, ColorInterp=Red
Band 2 Block=1591x1 Type=Byte, ColorInterp=Green
Band 3 Block=1591x1 Type=Byte, ColorInterp=Blue

Answer 1

Adjusting or adding a world file solves this easily.

The positive or negative direction of the first and fourth lines of a world file determine how the image reflects over an axis. To reflect an image over the x axis, flip the direction of the first line. To reflect an image over the y axis, flip the direction of the fourth line.

I think in your case the world file would simply be something like:

1 
0 
0
-1
0
0

If that produces the wrong reflection, then just flip the sign of the first or fourth line as needed.

Answer 2

You need to set the coordinate reference system, currently the Y-value is increasing in the wrong direction (unless you live in the southern hemisphere).