NAME¶
Image::Info - Extract meta information from image files (DEPRECATED)
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¶
Please note that this module is
deprecated and should not be used.
Alternatively, try one of the following modules:
Image::Size, Image::ExifTool.
The code in this module is old, unreviewed, hackish, still has numerous bugs and
is incomplete in quite a few cases.
While this module is sort-of maintained (e.g. the most critical security-related
bugs are fixed), no new features will be added and numerous minor bugs are
very likely sprinkled through the entire code base. You have been warned.
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( $file, key => value,... )
- This function takes the name of a file or a file handle as argument and
will return one or more hashes (actually hash references) describing the
images inside the file. If there is only one image in the file only one
hash is returned. In scalar context, only the hash for the first image is
returned.
In case of error, a hash containing the "error" key will be
returned. The corresponding value will be an appropriate error message.
If a reference to a scalar is passed as argument to this function, then it
is assumed that this scalar contains the raw image data directly.
The image_info() function also take optional key/value style
arguments that can influence what information is returned. See
Image::Info::XPM and other Image::Info submodules for the parameters that
they take.
- image_type( \$imgdata )
- Returns a hash with only one key, "file_type". The value will be
the type of the file. On error, sets the two keys "error" and
"Errno".
This function is a dramatically faster alternative to the image_info
function for situations in which you only need to find the image
type.
It uses only the internal file-type detection to do this, and thus does not
need to load any of the image type-specific driver modules, and does not
access to entire file. It also only needs access to the first 11 bytes of
the file.
To maintain some level of compatibility with image_info, image_type returns
in the same format, with the same error message style. That is, it returns
a HASH reference, with the "$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( $info_hash )
- Takes a hash as returned from image_info() and returns the
dimensions ($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 extention 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:
<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 tell which interlace method is
used.
- Compression
- This tells you which compression algorithm is used.
- Gamma
- A number.
- LastModificationTime
- A ISO date string
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 extention
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.
- 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 following web page contain
description of the fields that can be present:
http://www.ba.wakwak.com/~tsuruzoh/Computer/Digicams/exif-e.html
The "Exif" spec can be found at:
http://www.exif.org/specifications.html
- 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/>
- XBM
- See Image::Info::XBM for details.
- XPM
- See Image::Info::XPM for details.
CAVEATS¶
Note that while the module is still maintained, no new features will be added
and numerous bugs remain throughout the code base.
Especially the EXIF parsing code is buggy, not tested at all, and quite
incomplete (a lot of manufacturer's MakerNotes and tags are not parsed at
all). If you want a stable, feature-complete, up-to-date and tested EXIF
parsing library, please use Image::ExifTool.
Likewise, the image parsing code is quite hackish and seems to contain an
endless supply of bugs that crash, or hang with malformed input.
SEE ALSO¶
Image::Size, Image::ExifTool
AUTHORS¶
Copyright 1999-2004 Gisle Aas.
See the CREDITS file for a list of contributors and authors.
Now maintained by Tels - (c) 2006 - 2008.
LICENSE¶
This library is free software; you can redistribute it and/or modify it under
the same terms as Perl v5.8.8 itself.