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exif_read_data

(PHP 4 >= 4.2.0, PHP 5)

exif_read_data -- Reads the EXIF headers from JPEG or TIFF

Descripción

array exif_read_data ( string filename [, string sections [, bool arrays [, bool thumbnail]]] )

exif_read_data() reads the EXIF headers from a JPEG or TIFF image file. This way you can read meta data generated by digital cameras.

Exif headers tend to be present in JPEG/TIFF images generated by digital cameras, but unfortunately each digital camera maker has a different idea of how to actually tag their images, so you can't always rely on a specific Exif header being present.

Height and Width are computed the same way getimagesize() does so their values must not be part of any header returned. Also, html is a height/width text string to be used inside normal HTML.

When an Exif header contains a Copyright note, this itself can contain two values. As the solution is inconsistent in the Exif 2.10 standard, the COMPUTED section will return both entries Copyright.Photographer and Copyright.Editor while the IFD0 sections contains the byte array with the NULL character that splits both entries. Or just the first entry if the datatype was wrong (normal behaviour of Exif). The COMPUTED will also contain the entry Copyright which is either the original copyright string, or a comma separated list of the photo and editor copyright.

The tag UserComment has the same problem as the Copyright tag. It can store two values. First the encoding used, and second the value itself. If so the IFD section only contains the encoding or a byte array. The COMPUTED section will store both in the entries UserCommentEncoding and UserComment. The entry UserComment is available in both cases so it should be used in preference to the value in IFD0 section.

exif_read_data() also validates EXIF data tags according to the EXIF specification (http://exif.org/Exif2-2.PDF, page 20).

Nota: Windows ME/XP can both wipe the Exif headers when connecting to a camera. More information available at http://www.canon.co.jp/Imaging/NOTICE/011214-e.html.

Lista de parámetros

filename

The name of the image file being read. This cannot be an URL.

sections

Is a comma separated list of sections that need to be present in file to produce a result array. If none of the requested sections could be found the return value is FALSE.

FILEFileName, FileSize, FileDateTime, SectionsFound
COMPUTED html, Width, Height, IsColor, and more if available. Height and Width are computed the same way getimagesize() does so their values must not be part of any header returned. Also, html is a height/width text string to be used inside normal HTML.
ANY_TAGAny information that has a Tag e.g. IFD0, EXIF, ...
IFD0 All tagged data of IFD0. In normal imagefiles this contains image size and so forth.
THUMBNAIL A file is supposed to contain a thumbnail if it has a second IFD. All tagged information about the embedded thumbnail is stored in this section.
COMMENTComment headers of JPEG images.
EXIF The EXIF section is a sub section of IFD0. It contains more detailed information about an image. Most of these entries are digital camera related.

arrays

Specifies whether or not each section becomes an array. The sections COMPUTED, THUMBNAIL, and COMMENT always become arrays as they may contain values whose names conflict with other sections.

thumbnail

When set to TRUE the thumbnail itself is read. Otherwise, only the tagged data is read.

Valores retornados

It returns an associative array where the array indexes are the header names and the array values are the values associated with those headers. If no data can be returned, exif_read_data() will return FALSE.

Registro de cambios

VersiónDescripción
4.3.0 Can read all embedded IFD data including arrays (returned as such). Also the size of an embedded thumbnail is returned in a THUMBNAIL subarray, and can return thumbnails in TIFF format. Also, there is no longer a maximum length for returned values (not until the memory limit has been reached)
4.3.0 If PHP has mbstring support, the user comment can automatically change encoding. Also, if the user comment uses Unicode or JIS encoding this encoding will automatically be changed according to the exif ini settings in php.ini
4.3.0 If the image contains any IFD0 data then COMPUTED contains the entry ByteOrderMotorola which is 0 for little-endian (intel) and 1 for big-endian (motorola) byte order. Also, COMPUTED and UserComment no longer only contain the first copyright entry if the datatype was wrong.

Ejemplos

Ejemplo 1. exif_read_data() example

<?php
echo "test1.jpg:<br />\n";
$exif = exif_read_data('tests/test1.jpg', 'IFD0');
echo $exif===false ? "No header data found.<br />\n" : "Image contains headers<br />\n";

$exif = exif_read_data('tests/test2.jpg', 0, true);
echo "test2.jpg:<br />\n";
foreach ($exif as $key => $section) {
    foreach ($section as $name => $val) {
        echo "$key.$name: $val<br />\n";
    }
}
?>

The first call fails because the image has no header information.

El resultado del ejemplo seria algo similar a:

test1.jpg:
No header data found.
test2.jpg:
FILE.FileName: test2.jpg
FILE.FileDateTime: 1017666176
FILE.FileSize: 1240
FILE.FileType: 2
FILE.SectionsFound: ANY_TAG, IFD0, THUMBNAIL, COMMENT
COMPUTED.html: width="1" height="1"
COMPUTED.Height: 1
COMPUTED.Width: 1
COMPUTED.IsColor: 1
COMPUTED.ByteOrderMotorola: 1
COMPUTED.UserComment: Exif test image.
COMPUTED.UserCommentEncoding: ASCII
COMPUTED.Copyright: Photo (c) M.Boerger, Edited by M.Boerger.
COMPUTED.Copyright.Photographer: Photo (c) M.Boerger
COMPUTED.Copyright.Editor: Edited by M.Boerger.
IFD0.Copyright: Photo (c) M.Boerger
IFD0.UserComment: ASCII
THUMBNAIL.JPEGInterchangeFormat: 134
THUMBNAIL.JPEGInterchangeFormatLength: 523
COMMENT.0: Comment #1.
COMMENT.1: Comment #2.
COMMENT.2: Comment #3end
THUMBNAIL.JPEGInterchangeFormat: 134
THUMBNAIL.Thumbnail.Height: 1
THUMBNAIL.Thumbnail.Height: 1

Ver también

exif_thumbnail()
getimagesize()

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Generated: 2007-01-26 18:00:41