org.apache.commons.imaging.formats.png.scanlinefilters.ScanlineFilterSub Maven / Gradle / Ivy
/*
* 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.commons.imaging.formats.png.scanlinefilters;
import java.io.IOException;
import org.apache.commons.imaging.ImageReadException;
public class ScanlineFilterSub implements ScanlineFilter {
private final int bytesPerPixel;
public ScanlineFilterSub(final int bytesPerPixel) {
this.bytesPerPixel = bytesPerPixel;
}
public void unfilter(final byte[] src, final byte[] dst, final byte[] up)
throws ImageReadException, IOException {
for (int i = 0; i < src.length; i++) {
final int prevIndex = i - bytesPerPixel;
if (prevIndex >= 0) {
dst[i] = (byte) ((src[i] + dst[prevIndex]) % 256);
// dst[i] = 0xff & (src[i] + src[prevIndex]);
} else {
dst[i] = src[i];
}
// if(i<10)
// System.out.println("\t" + i + ": " + dst[i] + " (" + src[i] +
// ", " + prevIndex + ")");
// dst[i] = src[i];
}
}
}