/* * 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.pdfbox.pdmodel.graphics.predictor; /** * The sub algorithm. * * <code>Sub(i,j) = Raw(i,j) - Raw(i-1,j)</code> * * <code>Raw(i,j) = Sub(i,j) + Raw(i-1,j)</code> * * @author xylifyx@yahoo.co.uk * @version $Revision: 1.3 $ */ public class Sub extends PredictorAlgorithm { /** * {@inheritDoc} */ public void encodeLine(byte[] src, byte[] dest, int srcDy, int srcOffset, int destDy, int destOffset) { int bpl = getWidth()*getBpp(); int bpp = getBpp(); // case: x < bpp for (int x = 0; x < bpl && x < bpp; x++) { dest[x + destOffset] = src[x + srcOffset]; } // otherwise for (int x = getBpp(); x < bpl; x++) { dest[x + destOffset] = (byte) (src[x + srcOffset] - src[x + srcOffset - bpp]); } } /** * {@inheritDoc} */ public void decodeLine(byte[] src, byte[] dest, int srcDy, int srcOffset, int destDy, int destOffset) { int bpl = getWidth()*getBpp(); int bpp = getBpp(); // case: x < bpp for (int x = 0; x < bpl && x < bpp; x++) { dest[x + destOffset] = src[x + srcOffset]; } // otherwise for (int x = getBpp(); x < bpl; x++) { dest[x + destOffset] = (byte) (src[x + srcOffset] + dest[x + destOffset - bpp]); } } }