oracular (3) Image::Info.3pm.gz
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( $info_hash )
Returns the dimensions as a string suitable for embedding directly into HTML or SVG <img>-tags. E.g.:
print "<img src="..." @{[html_dim($info)]}>\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:
<res> <unit>
<xres> "/" <yres> <unit>
<xres> "/" <yres>
The <res>, <xres> and <yres> fields are numbers. The <unit> 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: <http://www.exif.org/specifications.html>.
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: <http://partners.adobe.com/public/developer/tiff/>
The EXIF spec can be found at: <http://www.exif.org/specifications.html>
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.