001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.imaging.formats.png.scanlinefilters; 018 019import java.io.IOException; 020 021import org.apache.commons.imaging.ImagingException; 022 023public class ScanlineFilterSub implements ScanlineFilter { 024 private final int bytesPerPixel; 025 026 public ScanlineFilterSub(final int bytesPerPixel) { 027 this.bytesPerPixel = bytesPerPixel; 028 } 029 030 @Override 031 public void unfilter(final byte[] src, final byte[] dst, final byte[] up) throws ImagingException, IOException { 032 for (int i = 0; i < src.length; i++) { 033 final int prevIndex = i - bytesPerPixel; 034 if (prevIndex >= 0) { 035 dst[i] = (byte) ((src[i] + dst[prevIndex]) % 256); 036 // dst[i] = 0xff & (src[i] + src[prevIndex]); 037 } else { 038 dst[i] = src[i]; 039 } 040 041 // if (i<10) 042 // System.out.println("\t" + i + ": " + dst[i] + " (" + src[i] + 043 // ", " + prevIndex + ")"); 044 045 // dst[i] = src[i]; 046 } 047 } 048}