Image::Info (3)

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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 provide 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 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

inpired 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:

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: <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 grafic.

TIFF

The "TIFF" spec can be found at: <partners.adobe.com/public/developer/tiff>

The

EXIF

spec can be found at: <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.

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 data. If you want an up-to-date and tested parsing library, please use Image::ExifTool.

SEE ALSO

Image::Size, Image::ExifTool

AUTHORS

Copyright 1999-2004 Gisle Aas.

See the

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.