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.icns;
18
19 import org.apache.commons.imaging.common.Allocator;
20
21 final class Rle24Compression {
22 public static byte[] decompress(final int width, final int height, final byte[] data) {
23 final int pixelCount = width * height;
24 final byte[] result = Allocator.byteArray(4 * pixelCount);
25
26 // Several ICNS parsers advance by 4 bytes here:
27 // https://code.google.com/archive/p/icns2png/ - when the width is >= 128
28 // https://icns.sourceforge.io/ - when those 4 bytes are all zero
29 //
30 // A scan of all .icns files on MacOS shows that
31 // all 128x128 images indeed start with 4 zeroes,
32 // while all smaller images don't.
33 // However it is dangerous to assume
34 // that 4 initial zeroes always need to be skipped,
35 // because they could encode valid pixels on smaller images.
36 // So always skip on 128x128, and never skip on anything else.
37 int dataPos = 0;
38 if (width >= 128 && height >= 128) {
39 dataPos = 4;
40 }
41
42 // argb, band by band in 3 passes, with no alpha
43 for (int band = 1; band <= 3; band++) {
44 int remaining = pixelCount;
45 int resultPos = 0;
46 while (remaining > 0) {
47 if ((data[dataPos] & 0x80) != 0) {
48 final int count = (0xff & data[dataPos]) - 125;
49 for (int i = 0; i < count; i++) {
50 result[band + 4 * resultPos++] = data[dataPos + 1];
51 }
52 dataPos += 2;
53 remaining -= count;
54 } else {
55 final int count = (0xff & data[dataPos]) + 1;
56 dataPos++;
57 for (int i = 0; i < count; i++) {
58 result[band + 4 * resultPos++] = data[dataPos++];
59 }
60 remaining -= count;
61 }
62 }
63 }
64 return result;
65 }
66
67 private Rle24Compression() {
68 }
69 }