| /* |
| * Copyright (c) 2000, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package com.sun.imageio.plugins.png; |
| |
| public class RowFilter { |
| |
| private static final int abs(int x) { |
| return (x < 0) ? -x : x; |
| } |
| |
| // Returns the sum of absolute differences |
| protected static int subFilter(byte[] currRow, |
| byte[] subFilteredRow, |
| int bytesPerPixel, |
| int bytesPerRow) { |
| int badness = 0; |
| for (int i = bytesPerPixel; i < bytesPerRow + bytesPerPixel; i++) { |
| int curr = currRow[i] & 0xff; |
| int left = currRow[i - bytesPerPixel] & 0xff; |
| int difference = curr - left; |
| subFilteredRow[i] = (byte)difference; |
| |
| badness += abs(difference); |
| } |
| |
| return badness; |
| } |
| |
| // Returns the sum of absolute differences |
| protected static int upFilter(byte[] currRow, |
| byte[] prevRow, |
| byte[] upFilteredRow, |
| int bytesPerPixel, |
| int bytesPerRow) { |
| int badness = 0; |
| for (int i = bytesPerPixel; i < bytesPerRow + bytesPerPixel; i++) { |
| int curr = currRow[i] & 0xff; |
| int up = prevRow[i] & 0xff; |
| int difference = curr - up; |
| upFilteredRow[i] = (byte)difference; |
| |
| badness += abs(difference); |
| } |
| |
| return badness; |
| } |
| |
| protected final int paethPredictor(int a, int b, int c) { |
| int p = a + b - c; |
| int pa = abs(p - a); |
| int pb = abs(p - b); |
| int pc = abs(p - c); |
| |
| if ((pa <= pb) && (pa <= pc)) { |
| return a; |
| } else if (pb <= pc) { |
| return b; |
| } else { |
| return c; |
| } |
| } |
| |
| public int filterRow(int colorType, |
| byte[] currRow, |
| byte[] prevRow, |
| byte[][] scratchRows, |
| int bytesPerRow, |
| int bytesPerPixel) { |
| |
| // Use type 0 for palette images |
| if (colorType != PNGImageReader.PNG_COLOR_PALETTE) { |
| System.arraycopy(currRow, bytesPerPixel, |
| scratchRows[0], bytesPerPixel, |
| bytesPerRow); |
| return 0; |
| } |
| |
| int[] filterBadness = new int[5]; |
| for (int i = 0; i < 5; i++) { |
| filterBadness[i] = Integer.MAX_VALUE; |
| } |
| |
| { |
| int badness = 0; |
| |
| for (int i = bytesPerPixel; i < bytesPerRow + bytesPerPixel; i++) { |
| int curr = currRow[i] & 0xff; |
| badness += curr; |
| } |
| |
| filterBadness[0] = badness; |
| } |
| |
| { |
| byte[] subFilteredRow = scratchRows[1]; |
| int badness = subFilter(currRow, |
| subFilteredRow, |
| bytesPerPixel, |
| bytesPerRow); |
| |
| filterBadness[1] = badness; |
| } |
| |
| { |
| byte[] upFilteredRow = scratchRows[2]; |
| int badness = upFilter(currRow, |
| prevRow, |
| upFilteredRow, |
| bytesPerPixel, |
| bytesPerRow); |
| |
| filterBadness[2] = badness; |
| } |
| |
| { |
| byte[] averageFilteredRow = scratchRows[3]; |
| int badness = 0; |
| |
| for (int i = bytesPerPixel; i < bytesPerRow + bytesPerPixel; i++) { |
| int curr = currRow[i] & 0xff; |
| int left = currRow[i - bytesPerPixel] & 0xff; |
| int up = prevRow[i] & 0xff; |
| int difference = curr - (left + up)/2;; |
| averageFilteredRow[i] = (byte)difference; |
| |
| badness += abs(difference); |
| } |
| |
| filterBadness[3] = badness; |
| } |
| |
| { |
| byte[] paethFilteredRow = scratchRows[4]; |
| int badness = 0; |
| |
| for (int i = bytesPerPixel; i < bytesPerRow + bytesPerPixel; i++) { |
| int curr = currRow[i] & 0xff; |
| int left = currRow[i - bytesPerPixel] & 0xff; |
| int up = prevRow[i] & 0xff; |
| int upleft = prevRow[i - bytesPerPixel] & 0xff; |
| int predictor = paethPredictor(left, up, upleft); |
| int difference = curr - predictor; |
| paethFilteredRow[i] = (byte)difference; |
| |
| badness += abs(difference); |
| } |
| |
| filterBadness[4] = badness; |
| } |
| |
| int minBadness = filterBadness[0]; |
| int filterType = 0; |
| |
| for (int i = 1; i < 5; i++) { |
| if (filterBadness[i] < minBadness) { |
| minBadness = filterBadness[i]; |
| filterType = i; |
| } |
| } |
| |
| if (filterType == 0) { |
| System.arraycopy(currRow, bytesPerPixel, |
| scratchRows[0], bytesPerPixel, |
| bytesPerRow); |
| } |
| |
| return filterType; |
| } |
| } |