1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.imaging.formats.png.scanlinefilters;
18
19 import java.io.IOException;
20
21 import org.apache.commons.imaging.ImagingException;
22
23 public class ScanlineFilterAverage implements ScanlineFilter {
24 private final int bytesPerPixel;
25
26 public ScanlineFilterAverage(final int bytesPerPixel) {
27 this.bytesPerPixel = bytesPerPixel;
28 }
29
30 @Override
31 public void unfilter(final byte[] src, final byte[] dst, final byte[] up) throws ImagingException, IOException {
32 for (int i = 0; i < src.length; i++) {
33 int raw = 0;
34 final int prevIndex = i - bytesPerPixel;
35 if (prevIndex >= 0) {
36 raw = dst[prevIndex];
37 }
38
39 int prior = 0;
40 if (up != null) {
41 prior = up[i];
42 }
43
44 final int average = ((0xff & raw) + (0xff & prior)) / 2;
45
46 dst[i] = (byte) ((src[i] + average) % 256);
47 // dst[i] = src[i];
48 // dst[i] = (byte) 255;
49 }
50 }
51 }