NAME

[% config.base %] - [% config.abstract %]

[% INCLUDE "warning" %]

SYNOPSIS

my $png = [% config.base %]->new ();
$png->read_file ("crazy.png");
printf "Your PNG is %d x %d\n", $png->width, $png->height;

General methods

new

my $png = [% config.base %]->new ();

Create a new PNG-file reading or writing object.

Options are

read

my $png = [% config.base %]->new ({read => 'some.png'});

Set the file to read. The file is then read at the time of object creation.

verbosity

my $png = [% config.base %]->new ({verbosity => 1});

If verbosity is set to a true value, print verbose messages about what the module is doing.

read_file

$png->read_file ("crazy.png")
    or die "Can't read it: " . $png->error ();

Read the PNG from the file name specified as the argument. This dies if there is an error.

write_file

$png->write_file ("crazy.png")
    or die "Can't write it: " . $png->error ();

Write the PNG to the file name specified as the argument. This dies if there is an error.

data

my $data = $png->data ();

Get the PNG image data as a Perl scalar.

error

Print the most recent error message.

PNG header-related methods

These methods are related to the PNG header (the IHDR chunk of the PNG file).

width

my $height = $png->width ();

Get the width of the current PNG image.

height

my $height = $png->height ();

Get the height of the current PNG image.

color_type

my $color_type = $png->color_type ();

Get the name of the colour type of the current PNG image. The possible return values are

PALETTE

GRAY

GRAY_ALPHA

RGB

RGB_ALPHA

bit_depth

my $bit_depth = $png->bit_depth ();

Get the bit depth of the current PNG image.

interlacing_method

my $interlacing_method = $png->interlacing_method

Get the name of the method of interlacing of the current PNG image.

There is no method for dealing with the compression method field of the header, since this only has one possible value.

Image data-related methods

rowbytes

my $rowbytes = $png->rowbytes;

This method returns the number of bytes in each row of the image. If no image has been read yet, it returns the undefined value.

rows

my $rows = $png->rows;

This method returns the rows of the image as an array reference which contains a number of elements equal to the height of the image. Each element has the length of the number of bytes in one row (as given by rowbytes) plus one final zero byte. The row data returned is binary data and may contain several bytes with the value zero.

Non-image chunks

text

my @text = $png->text;

Get the text chunks of the image. Each chunk is a hash reference with the keys being the fields of the PNG text chunk and the values being the values of those fields.

time

my $time_ref = $png->time;
print "The PNG was last modified in $time_ref->{year}.\n";

Get the last modified time of the image. The return value is a hash reference containing the following six fields,

year

month

day

hour

minute

second

These represent the last modification time of the image. The modification time of a PNG file is meant to be in the GMT (UCT) time zone so there is no time zone information in this.

If there is no last modification time, the undefined value is returned instead of a hash reference.

FUNCTIONS

There are some convenience functions in this module, exported on request.

display_text

use [% config.base %] qw/display_text/;
my @text = $png->text;
display_text ($text[3]);

Display the text chunk given as an argument on STDOUT.

This is meant as a minimal convenience function for when you are debugging or something rather than a general-purpose text chunk display routine.

SUPPORT

There is a mailing list for this Perl module at Google Groups. If you have a question or suggestion or bug report, please let me know via the mailing list. You don't have to join the mailing list to post a message.

SEE ALSO

In this distribution

[% config.base %]::Const

"[% config.base %]::Const" contains the libpng constants taken from the libpng header file "png.h".

[% config.base %]::Libpng

"[% config.base %]::Libpng" provides a Perl mirror of the interface of the C PNG library "libpng". [% config.base %] is built on top of this module.

libpng download

If you need to download libpng, see http://www.libpng.org/pub/png/libpng.html. See also "Alien::PNG".

[% INCLUDE "other_modules" %]

About the PNG format

Wikipedia article

There is http://en.wikipedia.org/wiki/Portable_Network_Graphics.

The PNG specification

[% INCLUDE "pngspec" %]

PNG The Definitive Guide by Greg Roelofs

The book "PNG - The Definitive Guide" by Greg Roelofs, published in 1999 by O'Reilly is available online at http://www.faqs.org/docs/png/. I didn't refer to this book at all in making [% config.base %], so I can't vouch for it, but looking at the contents pages it appears to contain a lot of useful information, although it is definitely showing its age, with chapters about software such as Netscape Navigator and BeOS.

[% INCLUDE "examples_doc" %]

[% INCLUDE "author" %]

cpanm Image::PNG

perl -MCPAN -e shell
install Image::PNG