gnu.javax.imageio.png

Class PNGFilter


public class PNGFilter
extends Object

A utility class of static methods implementing the PNG filtering algorithms.

Field Summary

static byte
FILTER_AVERAGE
static byte
FILTER_NONE
static byte
FILTER_PAETH
static byte
FILTER_SUB
static byte
FILTER_UP

Method Summary

static byte
chooseFilter(byte[] scanline, byte[] lastScanline, int bpp)
Heuristic for adaptively choosing a filter, following the scheme suggested in the PNG spec.
static byte[]
filterScanline(byte filtertype, byte[] scanline, byte[] lastScanline, int bpp)
Filter a scanline.
static byte[]
unFilterScanline(int filtertype, byte[] scanline, byte[] lastScanline, int bpp)
Unfilter a scanline.
static boolean
useFilter(PNGHeader header)
Return whether a filter should be used or FILTER_NONE, following the recommendations in the PNG spec.

Methods inherited from class java.lang.Object

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

FILTER_AVERAGE

public static final byte FILTER_AVERAGE
Field Value:
3

FILTER_NONE

public static final byte FILTER_NONE
Field Value:
0

FILTER_PAETH

public static final byte FILTER_PAETH
Field Value:
4

FILTER_SUB

public static final byte FILTER_SUB
Field Value:
1

FILTER_UP

public static final byte FILTER_UP
Field Value:
2

Method Details

chooseFilter

public static byte chooseFilter(byte[] scanline,
                                byte[] lastScanline,
                                int bpp)
Heuristic for adaptively choosing a filter, following the scheme suggested in the PNG spec.
Returns:
a fiter type.

filterScanline

public static byte[] filterScanline(byte filtertype,
                                    byte[] scanline,
                                    byte[] lastScanline,
                                    int bpp)
Filter a scanline.

unFilterScanline

public static byte[] unFilterScanline(int filtertype,
                                      byte[] scanline,
                                      byte[] lastScanline,
                                      int bpp)
Unfilter a scanline.

useFilter

public static boolean useFilter(PNGHeader header)
Return whether a filter should be used or FILTER_NONE, following the recommendations in the PNG spec.

PNGFilter.java -- PNG image filters. Copyright (C) 2006 Free Software Foundation This file is part of GNU Classpath. GNU Classpath is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. GNU Classpath 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 for more details. You should have received a copy of the GNU General Public License along with GNU Classpath; see the file COPYING. If not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. Linking this library statically or dynamically with other modules is making a combined work based on this library. Thus, the terms and conditions of the GNU General Public License cover the whole combination. As a special exception, the copyright holders of this library give you permission to link this library with independent modules to produce an executable, regardless of the license terms of these independent modules, and to copy and distribute the resulting executable under terms of your choice, provided that you also meet, for each linked independent module, the terms and conditions of the license of that module. An independent module is a module which is not derived from or based on this library. If you modify this library, you may extend this exception to your version of the library, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version.