Package com.twelvemonkeys.imageio.metadata.jpeg

Class JPEGQuality

  • public final class JPEGQuality
extends java.lang.Object
    Determines an approximate JPEG compression quality value from the quantization tables.
    Version:
    $Id: JPEGQuality.java,v 1.0 16.02.12 17:07 haraldk Exp$

    • Field Summary

      Fields 
      Modifier and Type Field Description
      (package private) static int DCT_SIZE_2  
      (package private) static int NUM_QUANT_TABLES  

    • Constructor Summary

      Constructors 
      Constructor Description
      JPEGQuality()  

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      private static int getJPEGQuality​(int[][] quantizationTables)  
      static float getJPEGQuality​(java.util.List<JPEGSegment> segments)
      Determines an approximate JPEG compression quality value from the quantization tables.
      static float getJPEGQuality​(javax.imageio.stream.ImageInputStream input)
      Determines an approximate JPEG compression quality value from the quantization tables.
      static javax.imageio.plugins.jpeg.JPEGQTable[] getQTables​(java.util.List<JPEGSegment> segments)  
      private static int[][] getQuantizationTables​(java.util.List<JPEGSegment> dqtSegments)  
      static void main​(java.lang.String[] args)  

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Constructor Detail

      • JPEGQuality

        public JPEGQuality()

    • Method Detail

      • getJPEGQuality

        public static float getJPEGQuality​(java.util.List<JPEGSegment> segments)
                            throws java.io.IOException
        Determines an approximate JPEG compression quality value from the quantization tables. The value will be in the range [0...1], where 1 is the best possible value.
        Parameters:
        segments - a list of JPEG segments containing the DQT quantization tables.
        Returns:
        a float in the range [0...1], representing the JPEG quality, or -1 if the quality can't be determined.
        Throws:
        javax.imageio.IIOException - if a JPEG format error is found during parsing.
        java.io.IOException - if an I/O exception occurs during parsing.
        See Also:
        ImageWriteParam.setCompressionQuality(float), JPEG.DQT

      • getJPEGQuality

        public static float getJPEGQuality​(javax.imageio.stream.ImageInputStream input)
                            throws java.io.IOException
        Determines an approximate JPEG compression quality value from the quantization tables. The value will be in the range [0...1], where 1 is the best possible value.
        Parameters:
        input - an image input stream containing JPEG data.
        Returns:
        a float in the range [0...1], representing the JPEG quality, or -1 if the quality can't be determined.
        Throws:
        javax.imageio.IIOException - if a JPEG format error is found during parsing.
        java.io.IOException - if an I/O exception occurs during parsing.
        See Also:
        ImageWriteParam.setCompressionQuality(float), JPEG.DQT

      • getJPEGQuality

        private static int getJPEGQuality​(int[][] quantizationTables)
                           throws java.io.IOException
        Throws:
        java.io.IOException

      • getQTables

        public static javax.imageio.plugins.jpeg.JPEGQTable[] getQTables​(java.util.List<JPEGSegment> segments)
                                                          throws java.io.IOException
        Throws:
        java.io.IOException

      • getQuantizationTables

        private static int[][] getQuantizationTables​(java.util.List<JPEGSegment> dqtSegments)
                                      throws java.io.IOException
        Throws:
        java.io.IOException

      • main

        public static void main​(java.lang.String[] args)
                 throws java.io.IOException
        Throws:
        java.io.IOException