    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 String PARAM_KEY_PNG_BIT_DEPTH = "PNG_BIT_DEPTH";
    029    public static final String PARAM_KEY_PNG_FORCE_INDEXED_COLOR = "PNG_FORCE_INDEXED_COLOR";
    030    public static final String PARAM_KEY_PNG_FORCE_TRUE_COLOR = "PNG_FORCE_TRUE_COLOR";
    031
    032    // public static final Object PARAM_KEY_PNG_BIT_DEPTH_YES = "YES";
    033    // public static final Object PARAM_KEY_PNG_BIT_DEPTH_NO = "NO";
    034
    035    public static final byte COMPRESSION_TYPE_INFLATE_DEFLATE = 0;
    036    public static final byte FILTER_METHOD_ADAPTIVE = 0;
    037
    038    /*
    039     * Background colour Solid background colour to be used when presenting the
    040     * image if no better option is available. Gamma and chromaticity Gamma
    041     * characteristic of the image with respect to the desired output intensity,
    042     * and chromaticity characteristics of the RGB values used in the image. ICC
    043     * profile Description of the colour space (in the form of an International
    044     * Color Consortium (ICC) profile) to which the samples in the image
    045     * conform. Image histogram Estimates of how frequently the image uses each
    046     * palette entry. Physical pixel dimensions Intended pixel size and aspect
    047     * ratio to be used in presenting the PNG image. Significant bits The number
    048     * of bits that are significant in the samples. sRGB colour space A
    049     * rendering intent (as defined by the International Color Consortium) and
    050     * an indication that the image samples conform to this colour space.
    051     * Suggested palette A reduced palette that may be used when the display
    052     * device is not capable of displaying the full range of colours in the
    053     * image. Textual data Textual information (which may be compressed)
    054     * associated with the image. Time The time when the PNG image was last
    055     * modified. Transparency Alpha information that allows the reference image
    056     * to be reconstructed when the alpha channel is not retained in the PNG
    057     * image.
    058     */
    059
    060    public static final String XMP_KEYWORD = "XML:com.adobe.xmp";
    061
    062    /**
    063     * Parameter key.
    064     *
    065     * <p>Only used when writing Png images.</p>
    066     *
    067     * <p>Valid values: a list of WriteTexts.</p>
    068     */
    069    public static final String PARAM_KEY_PNG_TEXT_CHUNKS = "PNG_TEXT_CHUNKS";
    070
    071    /**
    072     * Parameter key. Used in write operations to indicate the Physical Scale - sCAL.
    073     *
    074     * <p>Valid values: PhysicalScale</p>
    075     *
    076     * @see org.apache.commons.imaging.formats.png.PhysicalScale
    077     */
    078    public static final String PARAM_KEY_PHYSICAL_SCALE = "PHYSICAL_SCALE_CHUNK";
    079
    080    /**
    081     * Parameter key. Used to indicate the PNG compression level to be used.
    082     *
    083     * <p>For valid values, see {@link java.util.zip.Deflater}. If no value is specified, it will use
    084     * the default compression level.</p>
    085     *
    086     * @see java.util.zip.Deflater
    087     */
    088    public static final String PARAM_KEY_PNG_COMPRESSION_LEVEL = "PNG_COMPRESSION_LEVEL";
    089
    090    private PngConstants() {
    091    }
    092}