enhanced the (already fast!) png exporter

source/net/yacy/visualization/RasterPlotter.java

@@ -972,6 +972,7 @@ public class RasterPlotter {
 
     /*
      * The following code was transformed from a library, coded by J. David Eisenberg, version 1.5, 19 Oct 2003 (C) LGPL
+     * see: http://catcode.com/pngencoder/index.html
      * This code was very strongly transformed into the following very short method for an ultra-fast png generation.
      * These changes had been made 23.10.2012 by [MC] to the original code:
      * For the integration into YaCy this class was adopted to YaCy graphics by Michael Christen:
@@ -986,7 +987,7 @@ public class RasterPlotter {
      * - after all enhancements all class objects were removed; result is just one short static method
      * - made objects final where possible
      * - removed the PixelGrabber call and replaced it with a call to this.frame which is just a byte[]
-     * - added more speed woodoo like a buffer around the deflater which makes this much faster
+     * - added more speed voodoo like a buffer around the deflater which makes this much faster
      */
 
     private static final byte IHDR[] = {73, 72, 68, 82};
@@ -1000,7 +1001,7 @@ public class RasterPlotter {
 
         final Deflater scrunch = new Deflater(compressionLevel);
         ByteBuffer outBytes = new ByteBuffer(1024);
-        final OutputStream compBytes = new BufferedOutputStream(new DeflaterOutputStream(outBytes, scrunch));
+        final OutputStream compBytes = new BufferedOutputStream(new DeflaterOutputStream(outBytes, scrunch, 2048, false), 16384);
         int i = 0;
         for (int row = 0; row < height; row++) {
             compBytes.write(0);
@@ -1013,42 +1014,46 @@ public class RasterPlotter {
 
         // finally write the result of the concurrent calculation into an DeflaterOutputStream to compress the png
         final int nCompressed = outBytes.length();
-        final byte[] pngBytes = new byte[nCompressed + 57]; // yes thats the exact size, not too less, not too much. No resizing needed.
-        int bytePos = writeBytes(pngBytes, new byte[]{-119, 80, 78, 71, 13, 10, 26, 10}, 0);
-        final int startPos = bytePos = writeInt4(pngBytes, 13, bytePos);
-        bytePos = writeBytes(pngBytes, IHDR, bytePos);
-        bytePos = writeInt4(pngBytes, width, bytePos);
-        bytePos = writeInt4(pngBytes, height, bytePos);
-        bytePos = writeBytes(pngBytes, new byte[]{8, 2, 0, 0, 0}, bytePos);
+        final byte[] png = new byte[nCompressed + 57]; // yes thats the exact size, not too less, not too much. No resizing needed.
+        int next = writeBytes(png, new byte[]{-119, 80, 78, 71, 13, 10, 26, 10}, 0);
+        final int startPos = next = writeInt4(png, 13, next);
+        next = writeBytes(png, IHDR, next);
+        next = writeInt4(png, width, next);
+        next = writeInt4(png, height, next);
+        next = writeBytes(png, new byte[]{8, 2, 0, 0, 0}, next);
         final CRC32 crc = new CRC32();
         crc.reset();
-        crc.update(pngBytes, startPos, bytePos - startPos);
-        bytePos = writeInt4(pngBytes, (int) crc.getValue(), bytePos);
+        crc.update(png, startPos, next - startPos);
+        next = writeInt4(png, (int) crc.getValue(), next);
         crc.reset();
-        bytePos = writeInt4(pngBytes, nCompressed, bytePos);
-        bytePos = writeBytes(pngBytes, IDAT, bytePos);
+        next = writeInt4(png, nCompressed, next);
+        next = writeBytes(png, IDAT, next);
         crc.update(IDAT);
-        outBytes.copyTo(pngBytes, bytePos);
+        outBytes.copyTo(png, next);
         outBytes.close();
         outBytes = null;
-        crc.update(pngBytes, bytePos, nCompressed);
-        bytePos += nCompressed;
-        bytePos = writeInt4(pngBytes, (int) crc.getValue(), bytePos);
-        bytePos = writeInt4(pngBytes, 0, bytePos);
-        bytePos = writeBytes(pngBytes, IEND, bytePos);
+        crc.update(png, next, nCompressed);
+        next += nCompressed;
+        next = writeInt4(png, (int) crc.getValue(), next);
+        next = writeInt4(png, 0, next);
+        next = writeBytes(png, IEND, next);
         crc.reset();
         crc.update(IEND);
-        bytePos = writeInt4(pngBytes, (int) crc.getValue(), bytePos);
-        return pngBytes;
+        next = writeInt4(png, (int) crc.getValue(), next);
+        return png;
     }
 
-    private final static int writeInt4(final byte[] target, final int n, final int offset) {
-        return writeBytes(target, new byte[]{(byte) ((n >> 24) & 0xff), (byte) ((n >> 16) & 0xff), (byte) ((n >> 8) & 0xff), (byte) (n & 0xff)}, offset);
+    private final static int writeInt4(final byte[] target, final int n, int pos) {
+        target[pos++] = (byte) ((n >> 24) & 0xff);
+        target[pos++] = (byte) ((n >> 16) & 0xff);
+        target[pos++] = (byte) ((n >>  8) & 0xff);
+        target[pos++] = (byte) ( n        & 0xff);
+        return pos;
     }
 
-    private final static int writeBytes(final byte[] target, final byte[] data, final int offset) {
-        System.arraycopy(data, 0, target, offset, data.length);
-        return offset + data.length;
+    private final static int writeBytes(final byte[] target, final byte[] data, final int pos) {
+        System.arraycopy(data, 0, target, pos, data.length);
+        return pos + data.length;
     }
 
     public static void main(final String[] args) {