Ubuntu Manpage: Image::Info - Extract meta information from image files

Provided by: libimage-info-perl_1.44-2_all

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:

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.

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.