Image::Base::GD -- draw PNG format images

 use Image::Base::GD;
 my $image = Image::Base::GD->new (-width => 100,
                                   -height => 100);
 $image->rectangle (0,0, 99,99, 'white');
 $image->xy (20,20, 'black');
 $image->line (50,50, 70,70, '#FF00FF');
 $image->line (50,50, 70,70, '#0000AAAA9999');
 $image->save ('/some/filename.png');

Image::Base::GD is a subclass of Image::Base,

    Image::Base
      Image::Base::GD

Image::Base::GD extends Image::Base to create or update image files in various formats using the GD module and library (version 2 or higher).

Native GD drawing has many more features, but this module is an easy way to point Image::Base style code at a GD and is a good way to get PNG and other formats out of Image::Base code.

Colour names for drawing are from the GD::Simple->color_names() list (see GD::Simple), plus hex "#RRGGBB" or "#RRRRGGGGBBBB". Special colour "None" means transparent. Colours are allocated when first used. 4-digit "#RRRRGGGGBBBB" forms are truncated to the high 2 digits since GD works in 8-bit components.

GD can read and write the following formats

    png      with libpng
    jpeg     with libjpeg
    gif      unless disabled in GD.pm
    wbmp     wireless app bitmap
    gd       GD's own format, raw
    gd2      GD's own format, compressed

And read only,

    xpm      with libXpm
    xbm

PNG, JPEG and XPM depend on libgd being compiled with the respective support libraries. Perl GD interface has an option to disable GIF.

load() detect the format then calls the corresponding newFromPng() etc. "gd" format differs between libgd 1.x and 2.x. Both can be loaded, but libgd 2.x always writes 2.x format so that's what save() will give. "gd" is an uncompressed byte dump and mainly intended for temporary files.

WBMP is a bitmap format and is treated by GD as colours black "#000000" for 0 and white "#FFFFFF" for 1. On save anything except black is saved as 1, but it's probably not a good idea to depend on that.

It mostly works to pass in a GD::SVG::Image (see GD::SVG) as a -gd object and ask for -file_format "svg" to save, but don't rely on that quite yet since perhaps it'd be better as a subclass.

$image = Image::Base::GD->new (key=>value,...)

Create and return a new image object. A new image can be started with -width and -height,

    $image = Image::Base::GD->new (-width => 200, -height => 100);

Or an existing file can be read,

    $image = Image::Base::GD->new (-file => '/some/filename.png');

Or a GD::Image object can be given,

    $image = Image::Base::GD->new (-gd => $gdimageobject);

$new_image = $image->new (key=>value,...)

Create and return a copy of $image. The GD within $image is cloned (per $gd->clone). The optional parameters are applied to the new image as per set.

    # copy image, new compression level
    my $new_image = $image->new (-zlib_compression => 9);

$colour = $image->xy ($x, $y)

$image->xy ($x, $y, $colour)

Get or set an individual pixel.

Currently colours returned are in hex "#RRGGBB" form, or "None" for a fully transparent pixel. Partly transparent pixels are returned as a colour.

$image->rectangle ($x1,$y1, $x2,$y2, $colour, $fill)

Draw a rectangle with corners at $x1,$y1 and $x2,$y2. If $fill is true then it's filled, otherwise just the outline.

GD library 2.0.36 has a bug when drawing 1-pixel high $y1 == $y2 unfilled rectangles where it adds 3-pixel high sides to the result. Image::Base::GD has a workaround to avoid that. The intention isn't to second guess GD, but this fix is easy to apply and makes the output consistent with other Image::Base modules.

$image->ellipse ($x1,$y1, $x2,$y2, $colour)

$image->ellipse ($x1,$y1, $x2,$y2, $colour, $fill)

Draw an ellipse within the rectangle with top-left corner $x1,$y1 and bottom-right $x2,$y2. Optional $fill true means a filled ellipse.

In the current implementation ellipses with odd length sides (meaning $x2-$x1+1 and $y2-$y1+1 both odd numbers) are drawn with GD and the rest go to Image::Base because GD circa 2.0.36 doesn't seem to draw even widths very well. This different handling is a bit inconsistent.

$image->add_colours ($name, $name, ...)

Add colours to the GD palette. Colour names are the same as for the drawing functions.

    $image->add_colours ('red', 'green', '#FF00FF');

The drawing functions automatically add a colour if it doesn't already exist so add_colours in not needed, but it can be used to initialize the palette with particular desired colours.

For a truecolor GD add_colours does nothing since in that case each pixel has its own RGBA, rather than an index into a palette.

$image->load

$image->load ($filename)

Read the -file, or set -file to $filename and then read. This creates and sets a new underlying -gd because it's not possible to read into an existing GD image object, only a new one.

$image->save

$image->save ($filename)

Save to -file, or with a $filename argument set -file then save to that. The file format written is taken from the -file_format (see below).

-width (integer, read-only)

-height (integer, read-only)

The size of a GD image cannot be changed once created.

-ncolours (integer, read-only)

The number of colours allocated in the palette, or undef on a truecolor GD (which doesn't have a palette).

This count is similar to the -ncolours of Image::Xpm.

-file_format (string)

The file format as a string like "png" or "jpeg". See File Formats above for the choices.

After load() the -file_format is the format read. Setting -file_format can change the format for a subsequent save.

The default is "png", which means a newly created image (not read from a file) is saved as PNG by default.

-zlib_compression (integer 0-9 or -1, default -1)

The amount of data compression to apply when saving. The value is Zlib style 0 for no compression up to 9 for maximum effort. -1 means Zlib's default level (usually 6).

-gd

The underlying GD::Image object.

Putting colour "None" into pixels requires GD "alpha blending" turned off. Image::Base::GD turns off blending for GD objects it creates, but currently if you pass in a -gd then you must set the blending yourself if you're going to use None. Is that the best way? The ideal might be to save and restore while drawing None, but there's no apparent way to read the blending setting out of a GD to later restore. Alternately maybe turn blending off and leave it off on first drawing any None.

Image::Base, GD, GD::Simple, Image::Base::PNGwriter, Image::Xpm

http://user42.tuxfamily.org/image-base-gd/index.html

Image-Base-GD is Copyright 2010, 2011 Kevin Ryde

Image-Base-GD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.

Image-Base-GD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with Image-Base-GD. If not, see <http://www.gnu.org/licenses/>.