tim/prune/jpeg/ExifGateway.java

   1 package tim.prune.jpeg;
   2
   3 import java.io.File;
   4 import javax.swing.JOptionPane;
   5 import tim.prune.I18nManager;
   6
   7 /**
   8  * Skeleton gateway to the Exif functions.
   9  * This is required by Debian to divert Exif handling
  10  * to the external libmetadata-extractor-java library
  11  * instead of the included modified routines.
  12  *
  13  * Switching between internal and external libraries is
  14  * handled by the ExifLibrarySwitch
  15  */
  16 public abstract class ExifGateway
  17 {
  18         /** Library object to call */
  19         private static ExifLibrary _exifLibrary = null;
  20         /** Flag to set whether failure warning has already been shown */
  21         private static boolean _exifFailWarned = false;
  22
  23         /** Static block to initialise library */
  24         static
  25         {
  26                 String libraryClass = ExifLibrarySwitch.USE_INTERNAL_LIBRARY?"InternalExifLibrary":"ExternalExifLibrary";
  27                 try
  28                 {
  29                         _exifLibrary = (ExifLibrary) Class.forName("tim.prune.jpeg." + libraryClass).newInstance();
  30                 }
  31                 catch (Throwable nolib) {_exifLibrary = null;}
  32         }
  33
  34
  35         /**
  36          * Get the Jpeg data from the given file
  37          * @param inFile file to read
  38          * @return jpeg data, or null if none found
  39          */
  40         public static JpegData getJpegData(File inFile)
  41         {
  42                 try
  43                 {
  44                         // Call library (if found)
  45                         if (_exifLibrary != null) {
  46                                 JpegData data = _exifLibrary.getJpegData(inFile);
  47                                 return data;
  48                         }
  49                 }
  50                 catch (LinkageError nolib) {}
  51                 // Not successful - warn if necessary
  52                 if (!_exifFailWarned)
  53                 {
  54                         JOptionPane.showMessageDialog(null, I18nManager.getText("error.jpegload.exifreadfailed"),
  55                                 I18nManager.getText("error.jpegload.dialogtitle"), JOptionPane.WARNING_MESSAGE);
  56                         _exifFailWarned = true;
  57                 }
  58                 return null;
  59         }
  60
  61         /**
  62          * @return key to use to describe library, matching key for about dialog
  63          */
  64         public static String getDescriptionKey()
  65         {
  66                 String key = ExifLibrarySwitch.USE_INTERNAL_LIBRARY?"internal":"external";
  67                 if (_exifLibrary == null || !_exifLibrary.looksOK()) {key = key + ".failed";}
  68                 return key;
  69         }
  70
  71
  72
  73         /**
  74          * @param inNumerator numerator from Rational
  75          * @param inDenominator denominator from Rational
  76          * @return the value of the specified number as a positive <code>double</code>.
  77          * Prevents interpretation of 32 bit numbers as negative, and forces a positive answer
  78          */
  79         public static final double convertToPositiveValue(int inNumerator, int inDenominator)
  80         {
  81                 if (inDenominator == 0) return 0.0;
  82                 double numeratorDbl = inNumerator;
  83                 double denomDbl = inDenominator;
  84                 if (inNumerator >= 0)
  85                         return numeratorDbl / denomDbl;
  86                 final double correction = Math.pow(2.0, 32);
  87                 numeratorDbl += correction;
  88                 if (inDenominator < 0) denomDbl += correction;
  89                 return numeratorDbl / denomDbl;
  90         }
  91 }