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2004.06.29 17:01 "Saving Exif with TiffLib", by Jim Schueckler
> My task is to save Exif-data into tiff-images. According to Exif > specification I should put Exif-specific data into subIFDs, that are not > linked into common directories chain. And, as far as I understand, there > is no regular mechanism to create such IFDs, because SUBIFD tag, specified > by TiffLib has its own hardcoded value, while Exif-tags with offsets to > corresponding Exif-SubIFDs should have other values, that are defined by > Exif-standart. Should I modify TIffLib (add Exif-tags and made some > extension of SubIFD-mechanism) to solve my problems, or there is any other way? I've read the previous posts on this thread but did not include them to save bandwidth. My answer is directed to a possible format for the output file, and does not directly address using tifflib. We use our own code to do what tifflib does. Sorta' I recently had to implement putting EXIF data into TIFF files exported by the Kodak Professional DCS Photo Desk application. (Free at www.Kodak.com, search for "Photo Desk") Since the EXIF spec is really intended for camera-generated JPEG files, the spec does not strictly apply and can't be implemented for TIFF's exactly the same way. Therefore our main goal was to be as compatible as possible with other applications and to carry all the EXIF data so a TIFF file exported by Photo Desk could be re-opened by Photo Desk and then exported as a JPEG-EXIF file without losing any information. During development, I used several versions of Adobe Photoshop, Photo Studio ( free at http://www.stuffware.co.uk/photostudio ), and Apple's iPhoto to test that those apps could read the EXIF data. Your mileage may vary, but what I found to be most compatible is below. Note we only have one main image and its thumbnail, so this may not work exactly the same if the TIFF file has multiple images. If anybody would like me to send them an example TIFF file, (I can make a small image) ask me at James.Schueckler@Kodak.com 1. IFD0 contains the tag ExifIFD ( decimal 34665, hex 0x8769 ) that has the offset of the Exif IFD. 2. The EXIF IFD does not contain imageLength and imageWidth, etc. It just contains "camera data", which can include: ExposureTime, // 0x829A 33434 FNumber, // 0x829D 33437 ExposureProgram, // 0x8822 34850 ISOSpeedRatings, // 0x8827 34855 ExifVersion, // 0x9000 36864 DateTimeOriginal, // 0x9003 36867 DateTimeDigitized, // 0x9004 36868 ComponentsConfiguration, // 0x9101 37121 CompressedBitsPerPixel, // 0x9102 37122 ShutterSpeedValue, // 0x9201 37377 ApertureValue, // 0x9202 37378 BrightnessValue, // 0x9203 37379 ExposureBiasValue, // 0x9204 37380 MaxApertureValue, // 0x9205 37381 MeteringMode, // 0x9207 37383 LightSource, // 0x9208 37384 FlashTiffTag, // 0x9209 37385 FocalLength, // 0x920A 37386 // MakerNote, // 0x927C 37500 MakerNote CAUSES CRASHES // see http://www.x3f.info/technotes/FileDocs/MakerNoteDoc.html // My code does not copy MakerNote because there are different // interpretations of the "spec", some of which can cause a crash // if interpreted incorrectly. UserComment, // 0x9286 37510 FlashPixVersion, // 0xA000 40960 ColorSpace, // 0xA001 40961 FocalPlaneXResolutionExif, // 0xA20E 41486 FocalPlaneYResolutionExif, // 0xA20F 41487 FocalPlaneResolutionUnitExif,// 0xA210 41488 ExposureIndexExif, // 0xA215 41493 SensingMethodExif, // 0xA217 41495 FileSource, // 0xA300 41728 SceneType, // 0xA301 41729 CustomRendered, // 0xA401 41985 ExposureMode, // 0xA402 41986 WhiteBalanceExif, // 0xA403 41987 DigitalZoomRatio, // 0xA404 41988 FocalLengthIn35mmFilm, // 0xA405 41989 SceneCaptureType, // 0xA406 41990 GainControl, // 0xA407 41991 Contrast, // 0xA408 41992 Saturation, // 0xA409 41993 Sharpness, // 0xA40A 41994 SubjectDistanceRange, // 0xA40C 41996 GammaExif // 0xA500 42240 Jim Schueckler (585)726-6369 Professional Digital Cameras 1/205/KP kmx-236-6369 fax(585)726-6669 Eastman Kodak Company MS 03010 mailto:James.Schueckler@kodak.com 2400 Mt Read Boulevard http://www.kodak.com/go/kpdp Rochester NY 14650-3010 "Oh! I have slipped the surly bonds of earth..." J.G. McGee