Converting TIFF to JPG/GIF/PNG

[Andreas Hoeschler]

Hi all,

I have to convert TIFF --> JPG/GIF on the fly. The images stored in the 
database are in TIFF. The application (GNUstep tool) is supposed to 
return them in JPG/GIF or PNG format. On MacOSX I do

      NSBitmapImageRep *imageRep = [NSBitmapImageRep 
imageRepWithData:[_image
        TIFFRepresentationUsingCompression:NSTIFFCompressionLZW factor:15.0]];
      _jpgData = [[imageRep representationUsingType:NSJPEGFileType 
properties:properties] retain];

However, on GNUstep I get

Dec 06 14:53:01 MyTestApp[20679] Tiff Error (GSTiffWriteData) LZW 
compression no longer supported due to Unisys patent enforcement
Dec 06 14:53:01 MyTestApp[20679] Tiff Error (GSTiffWriteData) 2: Bad 
value for "ExtraSamples"

What are my options?

Thanks a lot,

   Andreas