From: Ou, Y. <Ye...@in...> - 2010-01-08 16:26:35
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Hi, I'm new to the metadata/exif. I would like to add Exif tags to both the jpeg and tiff files (and may be PNG) that might already have some Exif tags in them. I have these questions: 1) all libexif samples are shown with jpeg format. Since the same exif tags can be contained in the tiff file, will I be able to use the libexif library to add tags into the tiff file (or png)? 2) Does the libexif library support adding new exif tags to a jpeg or tiff file that is already have some others or same exif tags? The sample write_exif.c mentioned that libjpeg may be used for existing jpeg instead of the libexif? I'm not sure the difference between these two: the libexif and libjpeg. Thank you. Yech This message is intended only for the named recipient. If you are not the intended recipient, you are notified that disclosing, copying, distributing or taking any action based on the contents of this information is strictly prohibited. |
From: Dan F. <da...@co...> - 2010-01-08 20:28:27
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On Fri, Jan 08, 2010 at 10:25:54AM -0600, Ou, Yech wrote: > Hi, > I'm new to the metadata/exif. I would like to add Exif tags to both the jpeg > and tiff files (and may be PNG) that might already have some Exif tags in them. > I have these questions: > > 1) all libexif samples are shown with jpeg format. Since the same exif tags can > be contained in the tiff file, will I be able to use the libexif library to add > tags into the tiff file (or png)? libexif has only been used on EXIF files, to my knowledge. It only knows about tags from the EXIF specs and not general TIFF tags, so you'll need to clear the EXIF_DATA_OPTION_FOLLOW_SPECIFICATION and EXIF_DATA_OPTION_IGNORE_UNKNOWN_TAGS options. It should be possible to extract the TIFF tag block from the file and pass it in to exif_data_new_from_data() in order to use libexif. An enhancement request has already been created for this feature: http://sourceforge.net/tracker/?func=detail&aid=1957916&group_id=12272&atid=112272 > 2) Does the libexif library support adding new exif tags to a jpeg or tiff file > that is already have some others or same exif tags? The sample write_exif.c > mentioned that libjpeg may be used for existing jpeg instead of the libexif? > I'm not sure the difference between these two: the libexif and libjpeg. Yes, libexif allows adding tags to an existing JPEG file. See the action_set_value() code path in the exif front-end to see how that's done. libjpeg (which is included in the exif source code) is only used to insert the new EXIF tag block into the right location in the JPEG data stream of the original file. write-exif.c deliberately avoids writing to an existing file both to simplify the example and because libjpeg is included with exif and write-exif.c is part of libexif. >>> Dan -- http://www.MoveAnnouncer.com The web change of address service Let webmasters know that your web site has moved |