I use OSGeo4W on Windows 7 (64 bit) and included libpng16.dll When I try
C:\OSGeo4W64\bin>gdal_polygonize star.png bla
I get the following error:
ERROR 4: `star.png' does not exist in the file system, and is not recognised as a supported dataset name. Unable to open star.png
I copied star.png into C:\OSGeo4W64\bin (this is where gdal_polygonize batch file, python file and compiled python file are located )
What is the mistake?
UPDATE: I found out that I get the same mistake with a TIFF file but it works on JPEGs. Maybe the library/module for PNGs can't be found?