FOP-2336 OOM for tiff output

git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@1590653 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/fop/render/bitmap/AbstractBitmapDocumentHandler.java

         }
 
         //Set up bitmap to paint on
-        this.currentImage = createBufferedImage(bitmapWidth, bitmapHeight);
+        if (currentImage == null || currentImage.getWidth() != bitmapWidth || currentImage.getHeight() != bitmapHeight) {
+            currentImage = createBufferedImage(bitmapWidth, bitmapHeight);
+        }
         Graphics2D graphics2D = this.currentImage.createGraphics();
 
         // draw page background
                 this.multiImageWriter.writeImage(this.currentImage,
                         getSettings().getWriterParams());
             }
-            this.currentImage = null;
         } catch (IOException ioe) {
             throw new IFException("I/O error while encoding BufferedImage", ioe);
         }