/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.sanselan.formats.icns;
class Rle24Compression
{
public static byte[] decompress(int width, int height, byte[] data)
{
final int pixelCount = width * height;
final byte[] result = new byte[4 * pixelCount];
// Several ICNS parsers advance by 4 bytes here:
// http://code.google.com/p/icns2png/ - when the width is >= 128
// http://icns.sourceforge.net/ - when those 4 bytes are all zero
//
// A scan of all .icns files on MacOS shows that
// all 128x128 images indeed start with 4 zeroes,
// while all smaller images don't.
// However it is dangerous to assume
// that 4 initial zeroes always need to be skipped,
// because they could encode valid pixels on smaller images.
// So always skip on 128x128, and never skip on anything else.
int dataPos = 0;
if (width >= 128 && height >= 128)
dataPos = 4;
// argb, band by band in 3 passes, with no alpha
for (int band = 1; band <= 3; band++)
{
int remaining = pixelCount;
int resultPos = 0;
while (remaining > 0)
{
if ((data[dataPos] & 0x80) != 0)
{
int count = (0xff & data[dataPos]) - 125;
for (int i = 0; i < count; i++)
result[band + 4*(resultPos++)] = data[dataPos + 1];
dataPos += 2;
remaining -= count;
}
else
{
int count = (0xff & data[dataPos]) + 1;
dataPos++;
for (int i = 0; i < count; i++)
result[band + 4*(resultPos++)] = data[dataPos++];
remaining -= count;
}
}
}
return result;
}
}