Hello Joakim Joakim Knudsen <joakim.gr...@gmail.com> schrieb am Sa., 21. Mai 2016 um 19:29 Uhr:
> Hi List! > > I'm working on an Android app, where I want to read and write "EXIF tags" > to JPEG files on the device. Sanselan 0.97 seems to work perfectly, > although it's a bit complicated to work with EXIF tags/directories. > > The specific tags I'm interested in, is EXIF_TAG_USER_COMMENT and > EXIF_TAG_IMAGE_DESCRIPTION. > According to the documentation I could find, UserComment is of field type > "undefined", whereas ImageDescription is of field type ASCII. > > http://www.awaresystems.be/imaging/tiff/tifftags/privateifd/exif/usercomment.html > http://www.awaresystems.be/imaging/tiff/tifftags/imagedescription.html > > What's the proper way of creating those tags, wrt. charset etc? I want as > wide as possible character support (æøå etc). > > I find different discussions online, with different advice. Seems two > constructors are going around, where the simpler one does not deal with > charset/encoding at all. This one uses the .create method: > > String textToSet = "Some Text æøå"; > > TiffOutputField exif_comment = TiffOutputField.create( > TiffConstants.EXIF_TAG_USER_COMMENT, > outputSet.byteOrder, textToSet); > > > while this one uses the standard constructor: > > byte b[] = ExifTagConstants.EXIF_TAG_USER_COMMENT.encodeValue( > TiffFieldTypeConstants.FIELD_TYPE_ASCII, > textToSet, outputSet.byteOrder > ); > > // constructor arguments: taginfo tag fieldtype count bytes > TiffOutputField exif_comment2 = new > TiffOutputField(TiffConstants.EXIF_TAG_USER_COMMENT.tag, > TiffConstants.EXIF_TAG_USER_COMMENT, > TiffFieldTypeConstants.FIELD_TYPE_UNDEFINED, > b.length, b); > > In this last one, the string to set has been converted to a byte array > first. But can/should I set the encoding anywhere? > > Is the field type even ASCII? This information seems to indicate it's > not ASCII... > > http://www.awaresystems.be/imaging/tiff/tifftags/privateifd/exif/usercomment.html > > > Need some help here, as you can see, to get this right. The second > approach above does seem to work in my app, but I'd like to be sure > I'm not somehow messing up the JPEGs on the deviced. > I've looked at the code of org.apache.commons.imaging.formats.tiff.taginfos.TagInfoGpsText (ExifTagConstants.EXIF_TAG_USER_COMMENT is an instance of TagInfoGpsText). Here are my observations: - The FieldType parameter, which you have set to TiffFieldTypeConstants.FIELD_TYPE_ASCII is never used in the implemenation of encodeValue(FieldType, Object, ByteOrder) - When converting the input String to byte array, String.getBytes(String charsetName) is used - For charsetName "US-ASCII" is always used (it can not be configured by the user) So my guess is, that the code will not handle characters not in the US-ASCII charset correctly. Benedikt > > > > Joakim >
