Image::Info(3pm) - phpMan

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 provide functions to extract various kind 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, and 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 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 occured (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 use 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:

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 tell 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: <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 grafic.

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>

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.