NAME

Image::Info - Extract information from image files

NOTE

This is an alpha release of the Image::Info module. The interface to the routines described below is likely to change.

SYNOPSIS

use Image::Info qw(image_info dim);

my $info = image_info("image.jpg");
my($w, $h) = dim($info);

DESCRIPTION

This module provide functions to extract various information from image files. The following functions are provided:

image_info( $file )

This function takes the name of a file or a file handle as argument and will return one or more hashes 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.

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 into HTML tags like <img src="...">.

Image descriptions

The image_info() function return information about an image as a hash. The key values that can occur is based on the TIFF names.

The following names are common for any image format:

FileMediaType

This is the MIME type that is appropriate for the given file format. This is a string like: "image/png" or "image/jpeg".

FileExt

The is the suggested file name extention for a file of the given file format. It is a 3 letter, lowercase string like "png", "jpg".

ImageWidth

This is the number of pixels horizontally in the image.

ImageHeight

This is the number of pixels vertically in the image. (TIFF use the name ImageLength for this field.)

ColorType

This 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 to long, so we used the PNG term instead :-)

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 ColorType.

BitsPerSample

This says how many bits are used to encode each of samples. The number of numbers here should be the same as SamplesPerPixel.

Resolution

This field is instead of XResolution/YResolution when the pixels in the image are square.

ResolutionUnit

This is a string like dpi, dpm, dpcm giving the physical size of the image on screen or paper. If missing when XResolution/YResolution is present, then the resolution is used to denote the squareness of pixels in the image.

XResolution

The horizontal size of pixels.

YResolution

The vertical size of pixels.

Comment

Textual comments found in the file.

Interlace

If the image is interlaced, then this tell which interlace method is used.

Compression

This tell which compression algorithm is used.

Supported Image Formats

The following image file formats are supported:

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.

PNG

Information from IHDR, PLTE, gAMA, pHYs, tEXt, tIME chunks are extracted. The sequence of chunks are also given by the PNG_Chunks key.

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.

SEE ALSO

Image::Size

AUTHOR

Copyright 1999 Gisle Aas.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.