JRE 8 rt.jar is the JAR file for JRE 8 RT (Runtime) libraries. JRE (Java Runtime) 8 is the runtime environment included in JDK 8. JRE 8 rt.jar libraries are divided into 6 packages:

com.* - Internal Oracle and Sun Microsystems libraries
java.* - Standard Java API libraries.
javax.* - Extended Java API libraries.
jdk.* -  JDK supporting libraries.
org.* - Third party libraries.
sun.* - Old libraries developed by Sun Microsystems.

JAR File Information:

Directory of C:\fyicenter\jdk-1.8.0_191\jre\lib
      63,596,151 rt.jar

Here is the list of Java classes of the com.* package in JRE 1.8.0_191 rt.jar. Java source codes are also provided.

⏎ com/sun/image/codec/jpeg/JPEGEncodeParam.java

/*
 *
 * Copyright (c) 2007, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

/**********************************************************************
 **********************************************************************
 **********************************************************************
 *** COPYRIGHT (c) 1997-1998 Eastman Kodak Company.                 ***
 *** As  an unpublished  work pursuant to Title 17 of the United    ***
 *** States Code.  All rights reserved.                             ***
 **********************************************************************
 **********************************************************************
 **********************************************************************/

package com.sun.image.codec.jpeg;


/**
 * JPEGEncodeParam encapsulates tables and options necessary to
 * control encoding of JPEG data streams.  Parameters are either set
 * explicitly by the application for encoding, or read from another
 * JPEG header.<p>

 * When working with BufferedImages, the codec will attempt to match
 * the encoded JPEG COLOR_ID with the ColorModel in the BufferedImage.
 * This is not always possible (the default mappings are listed
 * below).  In cases where unsupported conversions are required (or
 * odd image colorspaces are in use) the user must either convert the
 * image data to a known ColorSpace or encode the data from a raster.
 * When encoding rasters no colorspace adjustments are made, so the
 * user must do any conversions required to get to the encoded
 * COLOR_ID.

 * The COLOR_ID for the encoded images is used to control the JPEG
 * codec's inital values for Huffman and Quantization Tables as well
 * as subsampling factors. It is also used to determine what color
 * conversion should be performed to obtain the best encoding.<p>

 * Note: The color ids described herein are simply enumerated values
 * that influence data processing by the JPEG codec.  JPEG compression
 * is, by definition, color blind.  These values are used as hints when
 * compressing JPEG data.  Through these values the JPEG codec can
 * perform some default rotation of data into spaces that will aid in
 * getting better compression ratios.<P>

 * Example behaviour is described below.  Since these mappings are
 * likely to change in the future it is strongly recommended that you
 * make use of the @see JPEGImageEncoder.getDefaultParamBlock calls
 * and check the encodedColorID for your particular BufferedImage.

 * In extreme cases is may be necessary for the user to convert the
 * image to the desired colorspace, and encode it from a Raster.  In
 * this case the API programmer must specify the colorID of the data
 * in the Raster and no color conversion will take place.
 <pre>
 ENCODING:

 BufferedImage Type/Instance        JPEG (Encoded) Color ID
 ========================       =======================
 TYPE_GRAY                      COLOR_ID_GRAYSCALE
 TYPE_RGB                       COLOR_ID_YCbCr
 TYPE_YCbCr                     COLOR_ID_YCbCr
 TYPE_YCbCr/CS_PYCC             COLOR_ID_PYCC
 TYPE_CMYK                      COLOR_ID_CMYK
 TYPE_RGB   (w/ alpha)          COLOR_ID_YCbCrA
 TYPE_YCbCr (w/ alpha)          COLOR_ID_YCbCrA
 TYPE_YCbCr/CS_PYCC (w/ alpha)  COLOR_ID_PYCCA
 ** Any Other **                COLOR_ID_UNKNOWN
 </pre>

 * When the user wants more control than the BufferedImage conversions
 * provide, the user must encode the data from a Raster. In this case
 * the data undergoes no color conversion at all. It is the user's
 * responsiblity to perform the desired conversions.<P>

 * If you intend to write a JFIF image (by including the APP0_MARKER)
 * the encoded COLOR_ID must be one of: COLOR_ID_UNKNOWN,
 * COLOR_ID_GRAYSCALE, COLOR_ID_YCbCr, or COLOR_ID_CMYK. In all other
 * instances an ImageformatException will be thrown.<P>

 * <B>IMPORTANT:</B> an Alpha RGB BufferedImage will not map to a
 * valid JFIF stream, you must strip off the alpha prior to encoding
 * if you want a JFIF file.  If the APP0 marker is set and you do not
 * strip off the Alpha, an ImageFormatException will be thrown.
 * <p>
 * Note that the classes in the com.sun.image.codec.jpeg package are not
 * part of the core Java APIs.  They are a part of Sun's JDK and JRE
 * distributions.  Although other licensees may choose to distribute these
 * classes, developers cannot depend on their availability in non-Sun
 * implementations.  We expect that equivalent functionality will eventually
 * be available in a core API or standard extension.
 * <p>
 */

public interface JPEGEncodeParam
        extends Cloneable, JPEGDecodeParam
{
        public Object clone();

        /**
         * Set the horizontal subsample factor for the given component.
         * Note that the subsample factor is the number of input pixels
         * that contribute to each output pixel (ussually 2 for YCC).
         * @param component The component being specified.
         * @param subsample The subsampling factor being specified.
         */
        public void setHorizontalSubsampling(int component,
                                                                                 int subsample);

        /**
         * Set the vertical subsample factor for the given component.  Note that
         * the subsample factor is the number of input pixels that
         * contribute to each output pixel (ussually 2 for YCC).
         * @param component The component being specified.
         * @param subsample The subsampling factor being specified.
         */
        public void setVerticalSubsampling(int component,
                                                                           int subsample);

        /**
         * Sets the coefficient quantization tables at index
         * passed. tableNum must range in value from 0 - 3.
         * @param qtable that will be used.
         * @param tableNum the index of the table to be set.
         */
        public void     setQTable( int tableNum, JPEGQTable qTable );

        /** Sets the DC Huffman coding table at index to the table provided.
         * @param huffTable JPEGHuffmanTable that will be assigned
         * to index tableNum.
         * @param tableNum - the index of the table to be set.
         * @exception IllegalArgumentException - thrown if the tableNum
         * is out of range.  Index must range in value from 0 - 3.
         */
        public void     setDCHuffmanTable( int tableNum,
                                                                   JPEGHuffmanTable huffTable);

        /** Sets the AC Huffman coding table at index to the table provided.
         * @param huffTable JPEGHuffmanTable that will be assigned
         * to index tableNum.
         * @param tableNum - the index of the table to be set.
         * @exception IllegalArgumentException - thrown if the tableNum
         * is out of range.  Index must range in value from 0 - 3.
         */
        public void     setACHuffmanTable( int tableNum,
                                                                   JPEGHuffmanTable huffTable);


        /**
         * Sets the mapping between a component and it's DC Huffman Table.
         * @param component The component to set the mapping for
         * @param table The DC Huffman table to use for component
         */
        public void setDCHuffmanComponentMapping( int component, int table);
        /**
         * Sets the mapping between a component and it's AC Huffman Table.
         * @param component The component to set the mapping for
         * @param table The AC Huffman table to use for component
         */
        public void setACHuffmanComponentMapping( int component, int table);
        /**
         * Sets the mapping between a component and it's Quantization Table.
         * @param component The component to set the mapping for
         * @param table The Quantization Table to use for component
         */
        public void setQTableComponentMapping( int component, int table);

        /**
         * Set the flag indicating the validity of the table information
         * in the ParamBlock.  This is used to indicate if tables should
         * be included when encoding.
         */
        public void setImageInfoValid(boolean flag);

        /**
         * Set the flag indicating the validity of the image information
         * in the ParamBlock.  This is used to indicates if image data
         * should be written when encoding.
         */
        public void setTableInfoValid(boolean flag);

        /**
         * Sets the marker data to be written to the output data stream.
         * This removes any existing marker data in the JPEParm object.
         * This can be used to remove the default APP0 marker by calling
         * it with data set to null.
         * @param marker The marker to set the data for.
         * @param data the new set of data to be written.
         */
        public void setMarkerData(int marker, byte[][] data);

        /**
         * Appends 'data' to the array of byte[] associated with
         * marker. This will result in additional instance of the marker
         * being written (one for each byte[] in the array.).
         * @param marker The marker to add and instance of.
         * @param data the data to be written.
         */
        public void addMarkerData(int marker, byte []data);

        /**
         * Set the MCUs per restart, or 0 for no restart markers.
         * @param restartInterval number MCUs per restart marker.
         */
        public void setRestartInterval( int restartInterval );


        /**
         * Set the pixel size units This value is copied into the APP0
         * marker (if that marker is written). This value isn't used by
         * the JPEG code.
         * @param unit One of the DENSITY_UNIT_* values.
         */
        public void setDensityUnit( int unit);
        /**
         * Set the horizontal pixel density This value is written into the
         * APP0 marker. It isn't used by the JPEG code.
         * @param density the horizontal pixel density, in units
         * described by @see JPEGParam.getDensityUnit.
         */
        public void setXDensity( int density );
        /**
         * Set the vertical pixel density.  This value is copied into
         * the JFIF APP0 marker. It isn't used by the JPEG code.
         * @param density The verticle pixel density, in units
         * described by @see JPEGParam.getDensityUnit.
         */
        public void setYDensity( int density );

        /**
         * This creates new Quantization tables that replace the currently
         * installed Quantization tables.  It also updates the Component
         * QTable mapping to the default for the current encoded COLOR_ID.

         * The Created Quantization table varies from very high
         * compression, very low quality, (0.0) to low compression, very
         * high quality (1.0) based on the quality parameter.<P>

         * At a quality level of 1.0 the table will be all 1's which will
         * lead to no loss of data due to quantization (however chrominace
         * subsampling, if used, and roundoff error in the DCT will still
         * degrade the image some what).<P>

         * This is a linear manipulation of the standard Chrominance
         * Q-Table.<P>

         * <pre>Some guidelines: 0.75 high quality
         *                 0.5  medium quality
         *                 0.25 low quality
         * </pre>
         * @param quality 0.0-1.0 setting of desired quality level.
         * @param forceBaseline force baseline quantization table
         */
        public void setQuality(float quality, boolean forceBaseline );
}

⏎ com/sun/image/codec/jpeg/JPEGEncodeParam.java

Or download all of them as a single archive file:

File name: jre-rt-com-1.8.0_191-src.zip
File size: 8099783 bytes
Release date: 2018-10-28
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