Class PngEncoder

  • All Implemented Interfaces:
    ImageEncoder

    public class PngEncoder
    extends java.lang.Object
    implements ImageEncoder
    PngEncoder takes a Java Image object and creates a byte string which can be saved as a PNG file. The Image is presumed to use the DirectColorModel.

    Thanks to Jay Denny at KeyPoint Software http://www.keypoint.com/ who let me develop this code on company time.

    You may contact me with (probably very-much-needed) improvements, comments, and bug fixes at:

    david@catcode.com

    This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version.

    This library 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 Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. A copy of the GNU LGPL may be found at http://www.gnu.org/copyleft/lesser.html

    Version:
    1.5, 19 Oct 2003

    CHANGES: -------- 19-Nov-2002 : CODING STYLE CHANGES ONLY (by David Gilbert for Object Refinery Limited); 19-Sep-2003 : Fix for platforms using EBCDIC (contributed by Paulo Soares); 19-Oct-2003 : Change private fields to protected fields so that PngEncoderB can inherit them (JDE) Fixed bug with calculation of nRows

    Author:
    J. David Eisenberg
    • Field Summary

      Fields 
      Modifier and Type Field Description
      static boolean ENCODE_ALPHA
      Constant specifying that alpha channel should be encoded.
      static int FILTER_LAST
      Constants for filter (LAST).
      static int FILTER_NONE
      Constants for filter (NONE).
      static int FILTER_SUB
      Constants for filter (SUB).
      static int FILTER_UP
      Constants for filter (UP).
      static boolean NO_ALPHA
      Constant specifying that alpha channel should not be encoded.
    • Constructor Summary

      Constructors 
      Constructor Description
      PngEncoder()
      Class constructor.
      PngEncoder​(java.awt.Image image)
      Class constructor specifying Image to encode, with no alpha channel encoding.
      PngEncoder​(java.awt.Image image, boolean encodeAlpha)
      Class constructor specifying Image to encode, and whether to encode alpha.
      PngEncoder​(java.awt.Image image, boolean encodeAlpha, int whichFilter)
      Class constructor specifying Image to encode, whether to encode alpha, and filter to use.
      PngEncoder​(java.awt.Image image, boolean encodeAlpha, int whichFilter, int compLevel)
      Class constructor specifying Image source to encode, whether to encode alpha, filter to use, and compression level.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void encodeImage​(java.awt.Image image, java.io.OutputStream outputStream, float quality, boolean encodeAlpha)
      Encodes the given image using the given encoder-specific quality and alpha-channel settings and writes the encoded image-data to the given stream.
      int getCompressionLevel()
      Retrieve compression level.
      boolean getEncodeAlpha()
      Retrieve alpha encoding status.
      int getFilter()
      Retrieve filtering scheme.
      java.awt.Image getImage()
      Returns the image to be encoded.
      java.lang.String getMimeType()
      Returns the mime-type of the encoded data.
      int getXDpi()
      Get the DPI for the X axis.
      int getYDpi()
      Get the DPI for the Y axis.
      byte[] pngEncode()
      Creates an array of bytes that is the PNG equivalent of the current image.
      byte[] pngEncode​(boolean encodeAlpha)
      Creates an array of bytes that is the PNG equivalent of the current image, specifying whether to encode alpha or not.
      void setCompressionLevel​(int level)
      Set the compression level to use.
      void setDpi​(int xDpi, int yDpi)
      Set the DPI resolution.
      void setEncodeAlpha​(boolean encodeAlpha)
      Set the alpha encoding on or off.
      void setFilter​(int whichFilter)
      Set the filter to use.
      void setImage​(java.awt.Image image)
      Set the image to be encoded.
      void setXDpi​(int xDpi)
      Set the DPI for the X axis.
      void setYDpi​(int yDpi)
      Set the DPI for the Y axis.
      • Methods inherited from class java.lang.Object

        equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Field Detail

      • ENCODE_ALPHA

        public static final boolean ENCODE_ALPHA
        Constant specifying that alpha channel should be encoded.
        See Also:
        Constant Field Values
      • NO_ALPHA

        public static final boolean NO_ALPHA
        Constant specifying that alpha channel should not be encoded.
        See Also:
        Constant Field Values
      • FILTER_NONE

        public static final int FILTER_NONE
        Constants for filter (NONE).
        See Also:
        Constant Field Values
      • FILTER_SUB

        public static final int FILTER_SUB
        Constants for filter (SUB).
        See Also:
        Constant Field Values
      • FILTER_UP

        public static final int FILTER_UP
        Constants for filter (UP).
        See Also:
        Constant Field Values
      • FILTER_LAST

        public static final int FILTER_LAST
        Constants for filter (LAST).
        See Also:
        Constant Field Values
    • Constructor Detail

      • PngEncoder

        public PngEncoder()
        Class constructor.
      • PngEncoder

        public PngEncoder​(java.awt.Image image)
        Class constructor specifying Image to encode, with no alpha channel encoding.
        Parameters:
        image - A Java Image object which uses the DirectColorModel
        See Also:
        Image
      • PngEncoder

        public PngEncoder​(java.awt.Image image,
                          boolean encodeAlpha)
        Class constructor specifying Image to encode, and whether to encode alpha.
        Parameters:
        image - A Java Image object which uses the DirectColorModel
        encodeAlpha - Encode the alpha channel? false=no; true=yes
        See Also:
        Image
      • PngEncoder

        public PngEncoder​(java.awt.Image image,
                          boolean encodeAlpha,
                          int whichFilter)
        Class constructor specifying Image to encode, whether to encode alpha, and filter to use.
        Parameters:
        image - A Java Image object which uses the DirectColorModel
        encodeAlpha - Encode the alpha channel? false=no; true=yes
        whichFilter - 0=none, 1=sub, 2=up
        See Also:
        Image
      • PngEncoder

        public PngEncoder​(java.awt.Image image,
                          boolean encodeAlpha,
                          int whichFilter,
                          int compLevel)
        Class constructor specifying Image source to encode, whether to encode alpha, filter to use, and compression level.
        Parameters:
        image - A Java Image object
        encodeAlpha - Encode the alpha channel? false=no; true=yes
        whichFilter - 0=none, 1=sub, 2=up
        compLevel - 0..9 (1 = best speed, 9 = best compression, 0 = no compression)
        See Also:
        Image
    • Method Detail

      • setImage

        public void setImage​(java.awt.Image image)
        Set the image to be encoded.
        Parameters:
        image - A Java Image object which uses the DirectColorModel
        See Also:
        Image, DirectColorModel
      • getImage

        public java.awt.Image getImage()
        Returns the image to be encoded.
        Returns:
        the image to be encoded.
      • pngEncode

        public byte[] pngEncode​(boolean encodeAlpha)
        Creates an array of bytes that is the PNG equivalent of the current image, specifying whether to encode alpha or not.
        Parameters:
        encodeAlpha - boolean false=no alpha, true=encode alpha
        Returns:
        an array of bytes, or null if there was a problem
      • pngEncode

        public byte[] pngEncode()
        Creates an array of bytes that is the PNG equivalent of the current image. Alpha encoding is determined by its setting in the constructor.
        Returns:
        an array of bytes, or null if there was a problem
      • setEncodeAlpha

        public void setEncodeAlpha​(boolean encodeAlpha)
        Set the alpha encoding on or off.
        Parameters:
        encodeAlpha - false=no, true=yes
      • getEncodeAlpha

        public boolean getEncodeAlpha()
        Retrieve alpha encoding status.
        Returns:
        boolean false=no, true=yes
      • setFilter

        public void setFilter​(int whichFilter)
        Set the filter to use.
        Parameters:
        whichFilter - from constant list
      • getFilter

        public int getFilter()
        Retrieve filtering scheme.
        Returns:
        int (see constant list)
      • setCompressionLevel

        public void setCompressionLevel​(int level)
        Set the compression level to use.
        Parameters:
        level - the compression level (1 = best speed, 9 = best compression, 0 = no compression)
      • getCompressionLevel

        public int getCompressionLevel()
        Retrieve compression level.
        Returns:
        int (1 = best speed, 9 = best compression, 0 = no compression)
      • setXDpi

        public void setXDpi​(int xDpi)
        Set the DPI for the X axis.
        Parameters:
        xDpi - The number of dots per inch
      • getXDpi

        public int getXDpi()
        Get the DPI for the X axis.
        Returns:
        The number of dots per inch
      • setYDpi

        public void setYDpi​(int yDpi)
        Set the DPI for the Y axis.
        Parameters:
        yDpi - The number of dots per inch
      • getYDpi

        public int getYDpi()
        Get the DPI for the Y axis.
        Returns:
        The number of dots per inch
      • setDpi

        public void setDpi​(int xDpi,
                           int yDpi)
        Set the DPI resolution.
        Parameters:
        xDpi - The number of dots per inch for the X axis.
        yDpi - The number of dots per inch for the Y axis.
      • encodeImage

        public void encodeImage​(java.awt.Image image,
                                java.io.OutputStream outputStream,
                                float quality,
                                boolean encodeAlpha)
                         throws java.io.IOException,
                                UnsupportedEncoderException
        Description copied from interface: ImageEncoder
        Encodes the given image using the given encoder-specific quality and alpha-channel settings and writes the encoded image-data to the given stream.
        Specified by:
        encodeImage in interface ImageEncoder
        Parameters:
        image - the image to be encoded.
        outputStream - the output stream, where to write the image data to.
        quality - the quality of the encoding.
        encodeAlpha - a flag controlling whether the alpha-channel should be encoded as well.
        Throws:
        java.io.IOException - if there was an IO error while generating or writing the image data.
        UnsupportedEncoderException - if the encoder is not supported.
      • getMimeType

        public java.lang.String getMimeType()
        Description copied from interface: ImageEncoder
        Returns the mime-type of the encoded data.
        Specified by:
        getMimeType in interface ImageEncoder
        Returns:
        the mime-type.