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XXVIII. Exif Functions
Introduktion
With the exif extension you are able to work with image meta data. For example, you may use exif functions to read meta data of pictures taken from digital cameras by working with information stored in the headers of the JPEG and TIFF images.
Systemkrav
Your PHP must be compiled in with --enable-exif. PHP does not require any additional library for the exif module. Windows users must also have the mbstring extension enabled.
Installation
To enable exif-support configure PHP with --enable-exif
Windows users must enable both the php_mbstring.dll and php_exif.dll DLL's in php.ini. The php_mbstring.dll DLL must be loaded before the php_exif.dll DLL so adjust your php.ini accordingly.
Runtime Konfiguration
Virkemåden af disse funktioner er berørt af indstillinger i php.ini.
Exif supports automatically conversion for Unicode and JIS character encodings of user comments when module mbstring is available. This is done by first decoding the comment using the specified characterset. The result is then encoded with another characterset which should match your HTTP output.
Tabel 1. Exif configuration options
| Name | Default | Changeable |
|---|---|---|
| exif.encode_unicode | "ISO-8859-15" | PHP_INI_ALL |
| exif.decode_unicode_motorola | "UCS-2BE" | PHP_INI_ALL |
| exif.decode_unicode_intel | "UCS-2LE" | PHP_INI_ALL |
| exif.encode_jis | "" | PHP_INI_ALL |
| exif.decode_jis_motorola | "JIS" | PHP_INI_ALL |
| exif.decode_jis_intel | "JIS" | PHP_INI_ALL |
Her er en kort forklaring på konfigurations-direktiverne.
- exif.encode_unicode string
exif.encode_unicode defines the characterset UNICODE user comments are handled. This defaults to ISO-8859-15 which should work for most non Asian countries. The setting can be empty or must be an encoding supported by mbstring. If it is empty the current internal encoding of mbstring is used.
- exif.decode_unicode_motorola string
exif.decode_unicode_motorola defines the image internal characterset for Unicode encoded user comments if image is in motorola byte order (big-endian). This setting cannot be empty but you can specify a list of encodings supported by mbstring. The default is UCS-2BE.
- exif.decode_unicode_intel string
exif.decode_unicode_intel defines the image internal characterset for Unicode encoded user comments if image is in intel byte order (little-endian). This setting cannot be empty but you can specify a list of encodings supported by mbstring. The default is UCS-2LE.
- exif.encode_jis string
exif.encode_jis defines the characterset JIS user comments are handled. This defaults to an empty value which forces the functions to use the current internal encoding of mbstring.
- exif.decode_jis_motorola string
exif.decode_jis_motorola defines the image internal characterset for JIS encoded user comments if image is in motorola byte order (big-endian). This setting cannot be empty but you can specify a list of encodings supported by mbstring. The default is JIS.
- exif.decode_jis_intel string
exif.decode_jis_intel defines the image internal characterset for JIS encoded user comments if image is in intel byte order (little-endian). This setting cannot be empty but you can specify a list of encodings supported by mbstring. The default is JIS.
Ressourcetyper
Denne udvidelse har ingen ressourcetyper defineret.
Foruddefinerede Konstanter
Konstanterne nedenunder er defineret af denne udvidelse, og vil kun være tilgængelige når denne udvidelse enten er blevet kompileret ind i PHP eller dynamisk indsat under runtime.
- EXIF_USE_MBSTRING (integer)
The exif_imagetype() lists several related built-in constants.
- Indholdsfortegnelse
- exif_imagetype -- Determine the type of an image
- exif_read_data -- Reads the EXIF headers from JPEG or TIFF
- exif_tagname -- Get the header name for an index
- exif_thumbnail -- Retrieve the embedded thumbnail of a TIFF or JPEG image
- read_exif_data -- Alias of exif_read_data()