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fpexif
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Overview
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fpexif is an fpc/Lazarus library for displaying and manipulating meta data in
image files.
fpexif works without the LCL.
Meta data systems supported are
- EXIF (including thumbnail, GPS, and manufacturer notes (partially) )
- IPTC
Image formats
- JPEG
- TIFF
The majority of meta data tags can be modified and written back to file. It
should be emphasized, however, that the EXIF maker notes are poorly documented
and often become unreadable after editing an EXIF structure.
Some examples in which fpexif can be applied:
- add user comments, keywords and other documentation
- fix date/time information (incorrect time/zone at camera when travelling
in foreign countries)
- adding GPS information to scanned photographs
- remember exposure settings of difficult photos
- extract thumbnails for a super-fast thumbnail viewer
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Quick introduction
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The basic class is TImgInfo (in unit fpeMetaData). It has properties to read
meta data from file/stream (LoadFromFile, LoadFromStream) and to write them
back (SaveToFile).
EXIF data found in the file are stored by the object ExifData from which every
tag can be acessed as TagByID[ATagID: TTagID] or TagByName[AName: String].
(TTagID is a DWord value containing the numerical ID of a tag in the low-word,
and the ID of the "directory" to which the tag belongs in the highword.)
The properties TagByID and TagByName return a TTag instance in which the tag
value is stored. The type of the value depends on the type of the tag and can
be accessed by calling AsString, AsInteger, Asfloat, AsIntegerArray,
AsFloatArray etc. TTag is declared in unit fpeTags.
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Example
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Read meta data from a file, write a particular tag, modify a tag, write back.
See also "console_demo".
uses
fpeMetadata, fpeTags;
var
imgInfo: TImgInfo;
tag: TTag;
begin
imgInfo := TImgInfo.Create;
try
// Read file
imgInfo.LoadFromFile('MyImage.jpg');
// Check for EXIF meta data
if imgInfo.HasEXIF then begin
// Read the shutter speed used when taking an image from EXIF data
WriteLn(
'ShutterSpeed: ',
imgInfo.ExifData.TagByName['ShutterSpeed'].AsString
);
// or better (to avoid the exception if this particular tag does not exist):
tag := imgInfo.ExifData.TagByName['ShutterSpeed'];
if tag <> nil then WriteLn('ShutterSpeed: ', tag.AsString);
// Add a user comment to the EXIF data
imgInfo.ExifData.TagByName['UserComment'].AsString := 'My best photo';
// Save the modified meta data to file
imgInfo.SaveToFile('MyImage_edited.jpg');
// or: imgInfo.Save; // overwrite currently loaded file
end;
finally
imgInfo.Free;
end;
end;
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Tested systems
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* Lazarus 1.0/fpc 2.6.0 up to Lazarus 1.9/fpc 3.0.4
* Delphi 7.0
* Delphi XE2
* Delphi 10.2 Tokyo
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License
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Modified LGPL (like Lazarus)
abb796c0b2