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;
018
019import org.apache.commons.imaging.common.BinaryConstant;
020
021public final class PngConstants {
022
023    public static final int COMPRESSION_DEFLATE_INFLATE = 0;
024
025    public static final BinaryConstant PNG_SIGNATURE = new BinaryConstant(
026            new byte[] { (byte) 0x89, 'P', 'N', 'G', '\r', '\n', 0x1A, '\n', });
027
028    public static final byte COMPRESSION_TYPE_INFLATE_DEFLATE = 0;
029    public static final byte FILTER_METHOD_ADAPTIVE = 0;
030
031    /*
032     * Background colour Solid background colour to be used when presenting the
033     * image if no better option is available. Gamma and chromaticity Gamma
034     * characteristic of the image with respect to the desired output intensity,
035     * and chromaticity characteristics of the RGB values used in the image. ICC
036     * profile Description of the colour space (in the form of an International
037     * Color Consortium (ICC) profile) to which the samples in the image
038     * conform. Image histogram Estimates of how frequently the image uses each
039     * palette entry. Physical pixel dimensions Intended pixel size and aspect
040     * ratio to be used in presenting the PNG image. Significant bits The number
041     * of bits that are significant in the samples. sRGB colour space A
042     * rendering intent (as defined by the International Color Consortium) and
043     * an indication that the image samples conform to this colour space.
044     * Suggested palette A reduced palette that may be used when the display
045     * device is not capable of displaying the full range of colours in the
046     * image. Textual data Textual information (which may be compressed)
047     * associated with the image. Time The time when the PNG image was last
048     * modified. Transparency Alpha information that allows the reference image
049     * to be reconstructed when the alpha channel is not retained in the PNG
050     * image.
051     */
052
053    public static final String XMP_KEYWORD = "XML:com.adobe.xmp";
054
055    /**
056     * Parameter key. Used to indicate the PNG compression level to be used.
057     *
058     * <p>For valid values, see {@link java.util.zip.Deflater}. If no value is specified, it will use
059     * the default compression level.</p>
060     *
061     * @see java.util.zip.Deflater
062     */
063    public static final String PARAM_KEY_PNG_COMPRESSION_LEVEL = "PNG_COMPRESSION_LEVEL";
064
065    private PngConstants() {
066    }
067}