Morgane Oger > Transform-Canvas > Transform::Canvas



Annotate this POD


Open  0
View/Report Bugs
Module Version: 0.15   Source  


Transform::Canvas - Perl extension for performing Coordinate transformation operations from the cartesion to the traditional drawing-model canvas coordinate systems.


VERSION 0.14 15 Febuary, 2009


  use Transform::Canvas;
  # create a mapping transform for data from 
  #x=-100,y=-100,x=100,y=100  to x=10,y=10,x=100,y=100
  $t = Transform::Canvas->new(canvas=>[10,10,100,100],data=>[-100,-100,100,100]);
  # create a arrays of x and y values
  $r_x = [-100,-10, 0, 20, 40, 60, 80, 100];
  $r_y = [-100,-10, 0, 20, 40, 60, 80, 100];
  #map the two arrays into the canvas data space
  ($pr_x,$pr_y) = $t->map($r_x,$r_y);


Transform::Canvas is a module which automates reference-frame transformations beween two cartesian coordinate systems. it is specifically intended to be used as a facilitator for coordinate-system transformation procedures between the traditional, right-hand-rule coordinate system used in mathematics graphing and the visual-arts coordinate system with a y-axis pointing down.

The module allows for arbitrary 2-D transform mappings.

Methods ^


Module constructor.

 #there are two ways to invoke this module
 #one-step constructo
 $t = Transform::Canvas->new (canvas => [x0 y0 x1 y1], data=>[x0 y0 x1 y1])
 # or two-step connstructor
 $t-> Transform::Canvas->new ();
 $t->prepareMap (canvas => [x0 y0 x1 y1], data=>[x0 y0 x1 y1])

generate the conversion object through which all data points will be passed. NB: svg drawings use the painter's model and use a coordinate system which starts at the top, left corner of the document and has x-axis increasing to the right and y-axis increasing down.

In certain drawings, the y-axis is inverted compared to mathematical representation systems which prefer y to increase in the upwards direction.

 canvas (target):
        x0 = paper-space minimum x value
        y0 = paper-space maximum x value
        x1 = paper-space minimum y value
        y1 = paper-space maximum y value
 data (source):
        x0 = data-space minimum x value
        y0 = data--space maximum x value
        x1 = data-space minimum y value
        y1 = data-space maximum y value

prepareMap hash %args

Prepare the transformation space for the conversions; Currently only handles linear transformations, but this is a perfect candidate for non-spacial, non-cartesian transforms...

sub cx0 [string $value]

set and/or return the canvas x min value

sub cx1 [string $value]

set and/or return the canvas x max value

sub cy0 [string $value]

set and/or return return the canvas y min value

sub cy1 [string $value]

set and/or return the canvas y max value

sub dx0 [string $value]

set and/or return the data space x min value

sub dx1 [string $value]

set and/or return the data space x max value

sub dy0 [string $value]

set and/or return the data space y min value

sub dy1 [string $value]

set and/or return the data space y max value.


Map an array or a value from the (x,y) data axes to the (x,y) canvas axes


Map an array or a value of the x data axis to the x canvas axis


Map an array or a value of the y data axis to the y canvas axis


Find th of an array

 my $x = $t->Max([1,2,3,4,5]);

This utility needed a home and this seems like a convenient place to stick it


Find th of an array

 my $x = $t->Max([1,2,3,4,5]);


SVG SVG::Parser SVG::DOM SVG::Element SVG::Graph SVG::Extension


Ronan Oger, <>


Copyright (C) 2004-2009 by Ronan Oger

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.3 or, at your option, any later version of Perl 5 you may have available.

syntax highlighting: