TiffRep from NSImage problem

[Iikka Virkkunen]

Dear list,

I wrote a small command line tool in Cocoa, which prepares my photos 
for web. I tried to port it to GNUStep, but run into trouble. The 
stripped down logic goes like this:

int main (int argc, const char * argv[]) {
  for (...) // for all input images
  {
        NSImage *retimg = ... //Create an empty NSImage
        NSImage *dimg = ... //Create an NSImage from the input file
	[retimg lockFocus]; // lock focus to retimg and draw the final image 
to it
                // draw background, scaled dimg and
                // nice corners with NSBezierPath
        [retimg unlockFocus];
        [[retimg TIFFRepresentation] writeToFile:outfilename atomically:NO];
   {
}
... but [retimb TIFFRepresentation] fails silently and returns nil.

So, I tried a workaround:

            [retimg lockFocus];
	    NSBitmapImageRep *tmpbmp = [[NSBitmapImageRep alloc] 
initWithFocusedViewRect: NSMakeRect(0,0,w,h)];
            [retimg unlockFocus];
	    [[tmpbmp TIFFRepresentation] writeToFile:outfilename 
atomically:NO];

... and got a critical error: initWithFocusedViewRect is not 
implemented.

So, what could be the reason my call to TIFFRepresentation fails?
How should I do this, then?

I'm building the tool with a primitive tool-makefile with -lgnustep-gui 
added to TOOL_LIBS.

Iikka