EXIF Metadata Extraction in Scala

by hohonuuli 1/07/2010 09:34:00 AM 3 comments

EXIF Metadata Extraction in Scala

Just for grins I ported the EXIF metadata extraction script in yesterdays post from Groovy to Scala. I ran into a few interesting gotchas while working with Scala.

• The class TiffConstants inherits a ton of constants (e.g. public static final ints) from other interfaces. However, in scala I had to explicitly use each interface where the constant was defined, using TiffConstants didn't work.
• There's no Grape for package management. Which is too bad, Scala would be far more useful if there was some equivalent; defining the classpath for a small script is annoying. My work around was just to embed the classpath in the shebang preamble.
• Got to remember to import implicit List conversions (i.e. import scala.collection.jcl.Conversions._) in order to work with Java Lists as Scala Lists

Here's the code:

#!/bin/sh
exec scala -cp $HOME/.groovy/grapes/org.apache.commons/sanselan/jars/sanselan-0.97.jar $0 $@
!#

import java.io.File
import org.apache.sanselan.{ImageReadException, Sanselan}
import org.apache.sanselan.common.{IImageMetadata, RationalNumber}
import org.apache.sanselan.formats.jpeg.JpegImageMetadata
import org.apache.sanselan.formats.tiff.{TiffField, TiffImageMetadata}
import org.apache.sanselan.formats.tiff.constants.{ExifTagConstants, GPSTagConstants, TagInfo, TiffConstants, TiffTagConstants}
import scala.collection.jcl.Conversions._

val file = new File(args(0))
val metadata = Sanselan.getMetadata(file)
def printTagValue(metadata: JpegImageMetadata, tagInfo: TagInfo): Unit = {
    val field = metadata.findEXIFValue(tagInfo)
    field match {
        case null => println("        (" + tagInfo.name + " not found.)")
        case _ => println("        " + tagInfo.name + ": " + field.getValueDescription())
    }
}

println("file:" + file.getPath())

if (metadata == null) {
    println("\tNo EXIF metadata was found")
}

if (metadata.isInstanceOf[JpegImageMetadata]) {
    val jpegMetadata = metadata.asInstanceOf[JpegImageMetadata]
    
    println("  -- Standard EXIF Tags")
    printTagValue(jpegMetadata,  TiffTagConstants.TIFF_TAG_XRESOLUTION)
    printTagValue(jpegMetadata,  TiffTagConstants.TIFF_TAG_DATE_TIME)
    printTagValue(jpegMetadata,  ExifTagConstants.EXIF_TAG_DATE_TIME_ORIGINAL)
    printTagValue(jpegMetadata,  ExifTagConstants.EXIF_TAG_CREATE_DATE)
    printTagValue(jpegMetadata,  ExifTagConstants.EXIF_TAG_ISO)
    printTagValue(jpegMetadata,  ExifTagConstants.EXIF_TAG_SHUTTER_SPEED_VALUE)
    printTagValue(jpegMetadata,  ExifTagConstants.EXIF_TAG_APERTURE_VALUE)
    printTagValue(jpegMetadata,  ExifTagConstants.EXIF_TAG_BRIGHTNESS_VALUE)
    printTagValue(jpegMetadata,  GPSTagConstants.GPS_TAG_GPS_LATITUDE_REF)
    printTagValue(jpegMetadata,  GPSTagConstants.GPS_TAG_GPS_LATITUDE)
    printTagValue(jpegMetadata,  GPSTagConstants.GPS_TAG_GPS_LONGITUDE_REF)
    printTagValue(jpegMetadata,  GPSTagConstants.GPS_TAG_GPS_LONGITUDE) 
    
    // simple interface to GPS data
    println("  -- GPS Info")
    val exifMetadata = jpegMetadata.getExif()
    if (exifMetadata != null) {
        val gpsInfo = exifMetadata.getGPS()   
        if (gpsInfo != null) {
            val longitude = gpsInfo.getLongitudeAsDegreesEast()
            val latitude = gpsInfo.getLatitudeAsDegreesNorth()
            
            println("        GPS Description: " + gpsInfo)
            println("        GPS Longitude (Degrees East): " + longitude)
            println("        GPS Latitude (Degrees North): " + latitude)
        }
    }
    
    println("  -- All EXIF info")
    jpegMetadata.getItems().foreach(item => println("        " + item))
    println("")
}