Image::Info(3) User Contributed Perl Documentation Image::Info(3)
NAME
Image::Info - Extract meta information from image files
SYNOPSIS
use Image::Info qw(image_info dim);
my $info = image_info("image.jpg");
if (my $error = $info->{error}) {
die "Can't parse image info: $error\n";
}
my $color = $info->{color_type};
my $type = image_type("image.jpg");
if (my $error = $type->{error}) {
die "Can't determine file type: $error\n";
}
die "No gif files allowed!" if $type->{file_type} eq 'GIF';
my($w, $h) = dim($info);
DESCRIPTION
This module provides functions to extract various kinds of meta
information from image files.
EXPORTS
Exports nothing by default, but can export the following methods on
request:
image_info
image_type
dim
html_dim
determine_file_type
METHODS
The following functions are provided by the "Image::Info" module:
image_info( $file )
image_info( \$imgdata )
image_info( $file, key => value,... )
This function takes the name of a file or a file handle as argument
and will return one or more hashes (actually hash references)
describing the images inside the file. If there is only one image
in the file only one hash is returned. In scalar context, only the
hash for the first image is returned.
In case of error, a hash containing the "error" key will be
returned. The corresponding value will be an appropriate error
message.
If a reference to a scalar is passed as an argument to this
function, then it is assumed that this scalar contains the raw
image data directly.
The image_info() function also take optional key/value style
arguments that can influence what information is returned.
image_type( $file )
image_type( \$imgdata )
Returns a hash with only one key, "file_type". The value will be
the type of the file. On error, sets the two keys "error" and
"Errno".
This function is a dramatically faster alternative to the
image_info function for situations in which you only need to find
the image type.
It uses only the internal file-type detection to do this, and thus
does not need to load any of the image type-specific driver
modules, and does not access to entire file. It also only needs
access to the first 11 bytes of the file.
To maintain some level of compatibility with image_info, image_type
returns in the same format, with the same error message style. That
is, it returns a HASH reference, with the "$type->{error}" key set
if there was an error.
On success, the HASH reference will contain the single key
"file_type", which represents the type of the file, expressed as
the type code used for the various drivers ('GIF', 'JPEG', 'TIFF'
and so on).
If there are multiple images within the file they will be ignored,
as this function provides only the type of the overall file, not of
the various images within it. This function will not return
multiple hashes if the file contains multiple images.
Of course, in all (or at least effectively all) cases the type of
the images inside the file is going to be the same as that of the
file itself.
dim( $info_hash )
Takes an hash as returned from image_info() and returns the
dimensions ($width, $height) of the image. In scalar context
returns the dimensions as a string.
html_dim( $info_hash )
Returns the dimensions as a string suitable for embedding directly
into HTML or SVG ![]()
-tags. E.g.:
print "
\n";
determine_file_format( $filedata )
Determines the file format from the passed file data (a normal Perl
scalar containing the first bytes of the file), and returns either
undef for an unknown file format, or a string describing the
format, like "BMP" or "JPEG".
Image descriptions
The image_info() function returns meta information about each image in
the form of a reference to a hash. The hash keys used are in most
cases based on the TIFF element names. All lower case keys are
mandatory for all file formats and will always be there unless an error
occurred (in which case the "error" key will be present.) Mixed case
keys will only be present when the corresponding information element is
available in the image.
The following key names are common for any image format:
file_media_type
This is the MIME type that is appropriate for the given file
format. The corresponding value is a string like: "image/png" or
"image/jpeg".
file_ext
The is the suggested file name extension for a file of the given
file format. The value is a 3 letter, lowercase string like "png",
"jpg".
width
This is the number of pixels horizontally in the image.
height
This is the number of pixels vertically in the image. (TIFF uses
the name ImageLength for this field.)
color_type
The value is a short string describing what kind of values the
pixels encode. The value can be one of the following:
Gray
GrayA
RGB
RGBA
CMYK
YCbCr
CIELab
These names can also be prefixed by "Indexed-" if the image is
composed of indexes into a palette. Of these, only "Indexed-RGB"
is likely to occur.
It is similar to the TIFF field "PhotometricInterpretation", but
this name was found to be too long, so we used the PNG inspired
term instead.
resolution
The value of this field normally gives the physical size of the
image on screen or paper. When the unit specifier is missing then
this field denotes the squareness of pixels in the image.
The syntax of this field is:
"/"
"/"
The , and fields are numbers. The is a
string like "dpi", "dpm" or "dpcm" (denoting "dots per
inch/cm/meter).
SamplesPerPixel
This says how many channels there are in the image. For some image
formats this number might be higher than the number implied from
the "color_type".
BitsPerSample
This says how many bits are used to encode each of samples. The
value is a reference to an array containing numbers. The number of
elements in the array should be the same as "SamplesPerPixel".
Comment
Textual comments found in the file. The value is a reference to an
array if there are multiple comments found.
Interlace
If the image is interlaced, then this tells which interlace method
is used.
Compression
This tells you which compression algorithm is used.
Gamma
A number.
LastModificationTime
A ISO date string
Supported Image Formats
The following image file formats are supported:
AVIF
Supports the basic standard info key names.
BMP This module supports the Microsoft Device Independent Bitmap format
(BMP, DIB, RLE).
For more information see Image::Info::BMP.
GIF Both GIF87a and GIF89a are supported and the version number is
found as "GIF_Version" for the first image. GIF files can contain
multiple images, and information for all images will be returned if
image_info() is called in list context. The Netscape-2.0 extension
to loop animation sequences is represented by the "GIF_Loop" key
for the first image. The value is either "forever" or a number
indicating loop count.
ICO This module supports the Microsoft Windows Icon Resource format
(.ico).
JPEG
For JPEG files we extract information both from "JFIF" and "Exif"
application chunks.
"Exif" is the file format written by most digital cameras. This
encode things like timestamp, camera model, focal length, exposure
time, aperture, flash usage, GPS position, etc.
The "Exif" spec can be found at:
.
The "color_type" element may have the following values: "Gray",
"YCbCr", and "CMYK". Note that detecting "RGB" and "YCCK" currently
does not work, but will hopefully in future.
PNG Information from IHDR, PLTE, gAMA, pHYs, tEXt, tIME chunks are
extracted. The sequence of chunks are also given by the
"PNG_Chunks" key.
PBM/PGM/PPM
All information available is extracted.
SVG Provides a plethora of attributes and metadata of an SVG vector
graphic.
TIFF
The "TIFF" spec can be found at:
The EXIF spec can be found at:
WBMP
wbmp files have no magic, so cannot be used with the normal
Image::Info functions. See Image::Info::WBMP for more information.
WEBP
VP8 (lossy), VP8L (lossless) and VP8X (extended) files are
supported. Sets the key "Animation" to true if the file is an
animation. Otherwise sets the key "Compression" to either "VP8" or
"Lossless".
XBM See Image::Info::XBM for details.
XPM See Image::Info::XPM for details.
CAVEATS
While this module is fine for parsing basic image information like
image type, dimensions and color depth, it is probably not good enough
for parsing out more advanced information like EXIF data. If you want
an up-to-date and tested EXIF parsing library, please use
Image::ExifTool.
SEE ALSO
Image::Size, Image::ExifTool
AUTHORS
Copyright 1999-2004 Gisle Aas.
See the CREDITS file for a list of contributors and authors.
Tels - (c) 2006 - 2008.
Current maintainer: Slaven Rezic - (c) 2008 - 2015.
LICENSE
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl v5.8.8 itself.
perl v5.42.0 2025-12-14 Image::Info(3)