reduced memory amount for network image

reduced also the number of memory allocation for image storage

source/net/yacy/visualization/RasterPlotter.java

@@ -929,9 +929,9 @@ public class RasterPlotter {
     
     public ByteBuffer exportPng() {
         try {
-            final ByteBuffer baos = new ByteBuffer();
-            byte[] pngbytes = pngEncode(1);
+            byte[] pngbytes = pngEncode(9);
             if (pngbytes == null) return null;
+            final ByteBuffer baos = new ByteBuffer(pngbytes.length);
             baos.write(pngbytes);
             baos.flush();
             baos.close();
@@ -1000,7 +1000,7 @@ public class RasterPlotter {
         final int height = image.getHeight(null);
 
         final Deflater scrunch = new Deflater(compressionLevel);
-        ByteBuffer outBytes = new ByteBuffer(1024);
+        ByteBuffer outBytes = new ByteBuffer(1024 * 300); // avoid frequent resizing of the ByteBuffer
         final OutputStream compBytes = new BufferedOutputStream(new DeflaterOutputStream(outBytes, scrunch, 2048, false), 16384);
         int i = 0;
         for (int row = 0; row < height; row++) {