It's not a perfect solution, but make it so we can call the tile trimming task and

not actually write out new image to a file if we don't need to. 

This cuts my tileset building from 42 seconds to 22 when no files have changed 
(as opposed to 4 when it was skipping it altogether, but winding up with a hosed 
tsbundles.dat), so it's at least a decent bit better.


git-svn-id: svn+ssh://src.earth.threerings.net/nenya/trunk@391 ed5b42cb-e716-0410-a449-f6a68f950b19

src/java/com/threerings/media/tile/util/TileSetTrimmer.java

@@ -151,11 +151,13 @@ public class TileSetTrimmer
             xoff += tb.width;
         }
 
-        // write out trimmed image
-        if (imgFormat == null || FastImageIO.FILE_SUFFIX.equals(imgFormat)) {
-            FastImageIO.write(image, destImage);
-        } else {
-            ImageIO.write(image, imgFormat, destImage);
+        if (destImage != null) {
+            // write out trimmed image
+            if (imgFormat == null || FastImageIO.FILE_SUFFIX.equals(imgFormat)) {
+                FastImageIO.write(image, destImage);
+            } else {
+                ImageIO.write(image, imgFormat, destImage);
+            }
         }
     }
 }