NAME

Image::Base::Tk::Canvas -- draw into Tk::Canvas

SYNOPSIS

use Image::Base::Tk::Canvas;
my $image = Image::Base::Tk::Canvas->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.eps');

CLASS HIERARCHY

Image::Base::Tk::Canvas is a subclass of Image::Base,

Image::Base
  Image::Base::Tk::Canvas

DESCRIPTION

Image::Base::Tk::Canvas extends Image::Base to add items to a Tk::Canvas widget. There's no file reading, but encapsulated postscript (EPS) can be written.

Tk::Canvas has more features than are available here, but this module is a novel way to point some Image::Base code at a canvas. In principle there's no limit on how many items a canvas can hold, but if drawing lots of individual pixels then Tk::Photo and Image::Base::Tk::Photo may be better.

Colours

Colour names are anything recognised by Tk_GetColor(3tk), which means X11 style

X server F<rgb.txt> names
#RGB            hex
#RRGGBB         hex
#RRRGGGBBB      hex
#RRRRGGGGBBBB   hex

Like Xlib, the shorter hex forms are padded with zeros, so "#FFF" means only "#F000F000F000", which is a light grey rather than white.

FUNCTIONS

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

Create and return a new canvas image object. A new canvas can be created with -width, -height, and a -for_widget which is its parent

$image = Image::Base::Tk::Canvas->new (-for_widget => $parent,
                                       -width => 200, -height => 100);

Or an existing Tk::Canvas object can be given,

$image = Image::Base::Tk::Canvas->new (-tkcanvas => $tkcanvas);

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

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

Get or set an individual pixel. Setting an individual pixel adds a 1x1 rectangle.

Getting a pixel is currently implemented by looking for an item at $x,$y and picking out its colour. This works well enough for the item types added by this module but may be wrong for others, in particular an item outline is not distinguished from its fill interior. "window" items are read with a Tk::WinPhoto and may be a bit slow (and might even induce an Xlib error if the window is off the edges of the screen). "bitmap" items are not read at all yet.

$image->diamond ($x0, $y0, $x1, $y1, $colour)

Draw a diamond shape within the rectangle top left ($x0,$y0) and bottom right ($x1,$y1) using $colour. If optional argument $fill is true then the diamond is filled.

In the current code a filled diamond uses a "polygon" item and an unfilled uses a "line" segments item. The line segments ensure interior points are not part of the diamond for find("overlapping") etc, the same as they're not for an unfilled ellipse or rectangle. Is that the best way?

$image->load ()

$image->load ($filename)

Currently there's no file format to read a canvas.

$image->save ()

$image->save ($filename)

Save encapsulated postscript to -file, or with a $filename argument set -file then save to that.

ATTRIBUTES

-width (integer)

-height (integer)

Setting these changes the size of the image.

-tkcanvas

The underlying Tk::Canvas object.

-file_format (string or undef)

The file format as a string like "png" or "jpeg", or undef if unknown or never set.

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

There's no attempt to check or validate the -file_format value, since it's possible to add new formats to Tk::Canvas at run time. Expect save() to croak if the format is unknown.

SEE ALSO

Image::Base, Tk::Canvas