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EXIF stands for Exchangeable Image File Format, and is a standard for storing interchange information in image files, especially those using JPEG compression.
Most digital cameras now use the EXIF format. The format is part of the DCF standard created by JEIDA to encourage interoperability between imaging devices.
This does not mean that there are files out there with an extension like ‘exif’ or ‘exf’. Digital cameras write EXIF information into jpeg files.
When we talk about EXIF information then we mean various image and camera attributes and in many cases a small thumbnail picture. Some example attributes:
- Artist
- Copyright
- Software
- Model
- DateTime
- ImageDescription
- ISOSpeedRatings-CCD sensitivity equivalent to Ag-Hr film speedrate TimeZoneOffset-Time Zone Offset (in hours) of DateTimeOriginal tag-value relative to Greenwich Mean Time
IPTC
The International Press Telecommunications Council, based in Windsor, United Kingdom, is a consortium of the world’s major news agencies and news industry vendors. It develops and maintains technical standards for improved news exchange that are used by virtually every major news organization in the world.
The IPTC was established in 1965 by a group of news organisations including the Alliance Européenne des Agences de Presse, ANPA (now NAA), FIEJ (now WAN) and the North American News Agencies (a joint committee of Associated Press, Canadian Press and United Press International) to safeguard the telecommunications interests of the world’s press.
In particular, the IPTC defined a set of metadata attributes that can be applied to images. You can embed the metadata into digital image files in the same way as EXIF data - known as "IPTC headers". IPTC Headers can be embedded into JPEG/EXIF or TIFF formatted image files.
EXIF and THBImage
There are two ways to access EXIF data using THB objects. The simple one is to use the THBImageEdit.Exif functions. They will return a list of EXIF data without providing a way to edit, add, delete entries and without any IPTC data. The advantage is that you don’t need the separate THBExi.dll.
If image tag data like EXIF and IPTC is an essential part of your application you should use the THBExif object.
Here we just describe THBExif functions and behavior.
You can use Exif and IPTC tags to attach additional infos to the image file.
You can use THBExif to read, edit or delete entries and write the modified tagset back to the original file, or into a new file.
When querying data you will get 5 columns per entry.
Tagname, TagID, Datatype, Datalength, Content
You can display or further process the extracted values.
Image.Make 271 Ascii 6 Canon
To get a list of all available datatypes refer to thbExifType.
There are many tags, a huge list defined by the EXIF standard and a huge amount of vendor specific tag sets.
You can refer to the EXIF specification at
http://www.exif.org
Here comes an example of what you will get.
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Image.Make 271 Ascii 6 Canon\r\n Image.Model 272 Ascii 20 Canon DIGITAL IXUS\r\n Image.Orientation 274 Short 1 1\r\n Image.XResolution 282 Rational 1 180/1\r\n Image.YResolution 283 Rational 1 180/1\r\n Image.ResolutionUnit 296 Short 1 2\r\n Image.DateTime 306 Ascii 20 2001:06:09 15:17:32\r\n Image.YCbCrPositioning 531 Short 1 1\r\n Image.ExifTag 34665 Long 1 184\r\n Photo.ExposureTime 33434 Rational 1 1/350\r\n Photo.FNumber 33437 Rational 1 40/10\r\n Photo.ExifVersion 36864 Undefined 4 48 50 49 48 \r\n Photo.DateTimeOriginal 36867 Ascii 20 2001:06:09 15:17:32\r\n Photo.DateTimeDigitized 36868 Ascii 20 2001:06:09 15:17:32\r\n Photo.ComponentsConfiguration 37121 Undefined 4 1 2 3 0 \r\n Photo.CompressedBitsPerPixel 37122 Rational 1 3/1\r\n Photo.ShutterSpeedValue 37377 SRational 1 553859/65536\r\n Photo.ApertureValue 37378 Rational 1 262144/65536\r\n Photo.ExposureBiasValue 37380 SRational 1 0/3\r\n Photo.MaxApertureValue 37381 Rational 1 194698/65536\r\n Photo.SubjectDistance 37382 Rational 1 3750/1000\r\n Photo.MeteringMode 37383 Short 1 2\r\n Photo.Flash 37385 Short 1 0\r\n Photo.FocalLength 37386 Rational 1 346/32\r\n Photo.UserComment 37510 Undefined 136 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 \r\n Photo.FlashpixVersion 40960 Undefined 4 48 49 48 48 \r\n Photo.ColorSpace 40961 Short 1 1\r\n Photo.PixelXDimension 40962 Short 1 640\r\n Photo.PixelYDimension 40963 Short 1 480\r\n Photo.InteroperabilityTag 40965 Long 1 1088\r\n Photo.FocalPlaneXResolution 41486 Rational 1 640000/206\r\n Photo.FocalPlaneYResolution 41487 Rational 1 480000/155\r\n Photo.FocalPlaneResolutionUnit 41488 Short 1 2\r\n Photo.SensingMethod 41495 Short 1 2\r\n Photo.FileSource 41728 Undefined 1 3 \r\n Canon.0x0002 2 Short 4 2 346 211 158\r\n Canon.0x0003 3 Short 4 0 0 0 0\r\n Canon.0x0000 0 Short 6 0 0 0 0 0 0\r\n Canon.ImageType 6 Ascii 32 IMG:JPEG file\r\n Canon.FirmwareVersion 7 Ascii 24 Firmware Version 1.0\r\n Canon.ImageNumber 8 Long 1 1010163\r\n Canon.OwnerName 9 Ascii 32 Peter Corrington\r\n Canon.0x0010 16 Long 1 100925440\r\n CanonCs1.Macro 1 Short 1 2\r\n CanonCs1.Selftimer 2 Short 1 0\r\n CanonCs1.Quality 3 Short 1 3\r\n CanonCs1.FlashMode 4 Short 1 1\r\n CanonCs1.DriveMode 5 Short 1 0\r\n CanonCs1.0x0006 6 Short 1 0\r\n CanonCs1.FocusMode 7 Short 1 1\r\n CanonCs1.0x0008 8 Short 1 0\r\n CanonCs1.0x0009 9 Short 1 1\r\n CanonCs1.ImageSize 10 Short 1 2\r\n CanonCs1.EasyMode 11 Short 1 1\r\n CanonCs1.DigitalZoom 12 Short 1 0\r\n CanonCs1.Contrast 13 Short 1 0\r\n CanonCs1.Saturation 14 Short 1 0\r\n CanonCs1.Sharpness 15 Short 1 0\r\n CanonCs1.ISOSpeed 16 Short 1 0\r\n CanonCs1.MeteringMode 17 Short 1 0\r\n CanonCs1.FocusType 18 Short 1 1\r\n CanonCs2.0x0001 1 Short 1 0\r\n CanonCs2.ISOSpeed 2 Short 1 140\r\n CanonCs2.0x0003 3 Short 1 258\r\n CanonCs2.TargetAperture 4 Short 1 128\r\n CanonCs2.TargetShutterSpeed 5 Short 1 270\r\n CanonCs2.0x0006 6 Short 1 0\r\n CanonCs2.WhiteBalance 7 Short 1 0\r\n CanonCs2.0x0008 8 Short 1 0\r\n CanonCs2.Sequence 9 Short 1 1\r\n CanonCs2.0x000a 10 Short 1 4\r\n CanonCs2.0x000b 11 Short 1 0\r\n CanonCs2.0x000c 12 Short 1 0\r\n CanonCs2.0x000d 13 Short 1 0\r\n CanonCs2.AFPointUsed 14 Short 1 12290\r\n Iop.InteroperabilityIndex 1 Ascii 4 R98\r\n Iop.InteroperabilityVersion 2 Undefined 4 48 49 48 48 \r\n Iop.RelatedImageWidth 4097 Short 1 640\r\n Iop.RelatedImageLength 4098 Short 1 480\r\n Thumbnail.Compression 259 Short 1 6\r\n Thumbnail.XResolution 282 Rational 1 180/1\r\n Thumbnail.YResolution 283 Rational 1 180/1\r\n Thumbnail.ResolutionUnit 296 Short 1 2\r\n Thumbnail.JPEGInterchangeFormat 513 Long 1 0\r\n Thumbnail.JPEGInterchangeFormatLength 514 Long 1 5342\r\n