Christopher Willmot > PostScript-Graph-1.02 > PostScript::Graph::Style

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Module Version: 1.02   Source  

NAME ^

PostScript::Graph::Style - style settings for postscript objects

SYNOPSIS ^

Simplest

Each time a new object is created the default style will be slightly different.

    use PostScript::File;
    use PostScript::Graph::Style;

    my $file = new PostScript::File();
    my $seq = new PostScript::Graph::Sequence();
    
    while (...) {
        my $style = new PostScript::Graph::Style(
                sequence => $seq,
                point    => {}
            );
        $style->write($file);
        
        $file->add_to_page( <<END_OF_CODE );
            % code using point variables...
            
            % setting colour or grey shade
            gpaperdict begin
                pocolor gpapercolor
            end

            % choosing a line width
            powidth setlinewidth
            
            % scaled relative to point sizing
            0 ppsize rlineto
            
            % showing the chosen point shape
            100 200 ppshape
    END_OF_CODE
    }

Typical

It is possible to control how each new object varies.

    my $seq = new PostScript::Graph::Sequence();
    $seq->setup( "red", [0, 1, 0.2, 0.8, 0.4, 0.6] );
    $seq->auto( qw(red green blue);
    
    my $file = new PostScript::File();
    while (...) {
        my $style = new PostScript::Graph::Style(
            sequence => $seq,
            bar      => {},
        );
        $style->write($file);
        
        ... postscript using bar variables ...
    }

Some of the styles may be overriden.

    my $style = new PostScript::Graph::Style(
                sequence  => $seq,
                auto      => [qw(color dashes)],
                line      => {
                    width        => 4,
                    outer_dashes => [],
                    outer_color  => [1, 0, 0],
                },
            );

Or the automatic default feature can be supressed and some or all details specified directly.

    my $style = new PostScript::Graph::Style(
                auto  => "none",
                point => {
                    shape => "circle",
                    size  => 12,
                },
            );

All options

    my $style = new PostScript::Graph::Style(
        sequence     => $seq,
        auto         => [qw(red green blue)],
        changes_only => 0,
        bgnd_outline         => 1,

        line => {
            color        => [0, 1, 0],
            inner_color  => [1, 1, 0],
            outer_color  => 0,
            dashes       => [3, 3],
            inner_dashes => [5, 2, 5, 10],
            outer_dashes => [],
            width        => 2,
            inner_width  => 2,
            outer_width  => 2.5,
        },

        point => {
            size         => 8,
            shape        => "diamond",
            color        => [0, 1, 0],
            inner_color  => [1, 1, 0],
            outer_color  => 0,
            width        => 2,
            inner_width  => 2,
            outer_width  => 2.5,
        },

        bar => {
            color        => [0, 1, 0],
            inner_color  => [1, 1, 0],
            outer_color  => 0,
            width        => 2,
            inner_width  => 2,
            outer_width  => 2.5,
        },
    );

DESCRIPTION ^

This module is designed as a supporting part of the PostScript::Graph suite. For top level modules that output something useful, see

    PostScript::Graph::Bar
    PostScript::Graph::Stock
    PostScript::Graph::XY

Style settings are provided for objects placed on a graph. Lines on the same graph need to be distinguishable from each other. Each line would have a PostScript::Graph::Style object holding its settings. Passing each line a reference to the same PostScript::Graph::Sequence object makes the styles vary. This can either use the defaults of be controlled to every last detail.

Settings are provided for three types of object. A line is any unfilled path, a bar is any filled path while a point is a filled path that may contain holes.

They all have outer and inner components. The inner component provides the main shape and colour, while the outer 'edge' is provided to insulate this from any background colour. Lines may be whole or broken and a variety of builtin shapes is provided. By default, repeated calls to new return styles that differ from one another although like everything else this can be under detailed user control if required.

The settings are only useful once they have been written out to a PostScript::File object using write. The following functions return values set in the constructor. See "new" for more details.

    bar_outer_color()
    bar_outer_width()
    bar_inner_color()
    bar_inner_width()

    color()
    
    line_outer_color()
    line_outer_width()
    line_outer_dashes()
    line_inner_color()
    line_inner_width()
    line_inner_dashes()

    point_size()
    point_shape()
    point_outer_color()
    point_outer_width()
    point_inner_color()
    point_inner_width()

    bgnd_outline()
    sequence()

Style Generation

Although it is possible to specify styles directly, mostly the style just needs to be different from the last one. These dynamic defaults provide around 3600 variations which should be suitable for most cases. The values themselves can be replaced if desired. Permutations of these are then generated on demand and the permutation order is also under user control.

PostScript::Graph::Sequence new

Whenever a new PostScript::Graph::Style object is created, it uses certain defaults. These defaults can be made to vary if a sequence is declared as one of the options. This should be the value returned from:

    my $seq = new PostScript::Graph::Sequence();

setup( key, array )

The defaults provided by the PostScript::Graph::Sequence are chosen from arrays which may be redefined using this method. Note that it is a PostScript::Graph::Sequence method and NOT a PostScript::Graph::Style method, and should typically be called directly after the PostScript::Graph::Sequence object is created.

Example

    use PostScript::Graph::Style;
    
    my $seq = new PostScript::Graph::Sequence();
    $seq->setup( "red", [0, 0.5, 1] );

array is always an array reference as in the example. key may be one of the following.

    red     green   blue
    gray    color   width
    dashes  shape   size

Mostly, their arrays contain integers (0 to 1.0 for colours). The exceptions are dashes, shape, color and possibly gray.

See "inner_dashes" for details on the arrays required for dashes. Suitable values for shape can be one of these entries, taken from the default array.

    my $seq = new PostScript::Graph::Sequence();
    $seq->setup( "shape",
        [ qw(cross plus dot circle square diamond) ]);

If the gray array is filled with decimals between 0 and 1 (inclusive), the result is varying shades of grey. It is also possible to use arrays of red-green-blue colours:

    my $seq = new PostScript::Graph::Sequence();
    $seq->setup( "color",
        [ [ 0, 0, 0 ],      # white
          [ 0, 0, 1 ],      # blue
          [ 0, 1, 0 ],      # green
          [ 0, 1, 1 ],      # cyan
          [ 1, 0, 0 ],      # red
          [ 1, 0, 1 ],      # mauve
          [ 1, 1, 0 ],      # yellow
          [ 1, 1, 1 ], ]);  # black

    my $gs = new PostScript::Graph::Style(
                auto  => [qw(color)],
                bar   => {},
            );

The full range of colours may be used provided that the 'bgnd_outline' style option has not been set. By default each line, point and bar are outlined in the complementary colour to the background, making them stand out.

More than one variable can be set of course. For example the following would ensure lines with 15 shades of red-orange-yellow, if 'auto' was set to some combination of red, blue and green.

    my $seq = new PostScript::Graph::Sequence();
    $seq->setup("red", [ 0.2, 1, 0.4, 0.8, 0.6 ]);
    $seq->setup("green", [ 0, 0.8, 0.4 ]);
    $seq->setup("blue", [ 0 ]);

auto( list )

Specify which defaults are changed for each new style.

The first feature mentioned will vary fastest from one style to the next while the last varies slowest. Any features not mentioned will not be varied. See "Style Generation" for how to change the defaults for these features.

    red     green   blue
    gray    color   width
    dashes  shape   size

If not set directly, it may be set from the auto option given to the first PostScript::Graph::Style object created using this sequence.

reset()

Starts the sequence of defaults again.

default()

Return a fallback PostScript::Graph::Sequence. Note that these are global settings possibly called by many, unrelated objects, so the sequences generated may not be predictable or even useful.

Class Methods

### PostScript::Graph::Style

CONSTRUCTOR ^

new( [options] )

options can either be a list of hash keys and values or a single hash reference. In both cases the hash must have the same structure. There are a few principal keys and most of these refer to hashes holding a group of options.

It is essential that at least one of line, point or bar is given, even if the hashes are empty. Otherwise no style settings will actually be output.

Global settings

These are mainly concerned with how the defaults are generated for each new PostScript::Graph::Style object.

auto

Setting auto to the string 'none' prevents the automatic generation of defaults. Of course the same result could be obtained by setting every option so the defaults are never needed. Otherwise this may be a list of features (see the auto method for PostScript::Graph::Sequence, above).

changes_only

Set this to 0 if you need every style parameter written out to postscript. If this is 1, only the changes from the previous style settings are added to the file. (Default: 1)

color

Set default colour for lines, bars and points.

label

A string identifying the style, added to the id(). The interaction between styles can get quite complex, especially when using more than one sequence. This label becomes part of the id method and makes styles easier to track.

bgnd_outline

By default, the outer colour is the complement of the background (see "outer_color"). Setting this to 1 makes the outer colour the same as the background.

sequence

This identifies a sequence of default values. If this is not defined (but 'auto' is not 'none'), a new sequence would be created with each call resulting in the same style every time.

use_color

Set this to 0 to use shades of grey for monochrome printers.

This also must be set to 0 to cycle through user defined colours. See "Style Generation" for how to set those. This switch actually determines whether the colour value is taken from the gray array or a composite of the red, green and blue arrays. So putting the custom colours into 'gray' and setting color to 0 reads these. The internal postscript code handles each format interchangeably, so the result is coloured gray!

width

Set default line width for lines, bars and points.

Graphic settings

The options described below belong within line, bar or point sub-hashes unless otherwise mentioned. For example, referring to the descriptions for color and size:

    line  => { color => ... }       valid
    point => { color => ... }       valid
    
    line  => { size => ... }        NOT valid
    point => { size => ... }        valid

The sub-hashes are significant. They should be present if that feature is to be used, even if the sub-hash is empty. Otherwise, no postscript values of that type will be defined.

All color options within these sub-hashes take either a single greyscale decimal or a reference to an array holding decimals for red, green and blue components. All decimals should be between 0 and 1.0 inclusive.

    color       => 1                white
    outer_color => 0                black
    inner_color => [1, 0, 0]        red

Example 2

    $ps = new PostScript::Graph::Style(
            auto  => "none",
            line  => {
                width       => 2,
                inner_color => [ 1, 0.6, 0.4 ],
            }
            point => {
                shape       => "diamond",
                size        => 12,
                color       => [ 1, 0.8, 0.8 ],
                inner_width => 2,
                outer_width => 1,
            }
        );

color

A synonym for inner_color. See "new".

dashes

Set both inner and outer dash patterns. See "inner_dashes".

inner_color

The main colour of the line or point. See "new".

inner_dashes

This array ref holds values that determine any dash pattern. They are repeated as needed to give the size 'on' then 'off'. Examples are the best way to describe this.

    inner_dashes => []          -------------------------
    inner_dashes => [ 3,3 ]     ---   ---   ---   ---   -
    inner_dashes => [ 5,2,1,2 ] -----  -  -----  -  -----

Only available for lines.

inner_width

The size of the central portion of the line. Although this can be set of points, size is more likely to be what you want. Probably should be no less than 0.1 to be visible - 0.24 on a 300dpi device or 1 on 72dpi. (Default: 0.5)

When used in conjunction with inner_dashes, setting inner and outer widths to the same value produces a two-colour dash.

outer_color

Colour for the 'edges' of the line or point. To be visible outer_width must be greater than <inner_width>. (Default: -1)

Note that the default is NOT a valid postscript value (although gpapercolor handles it fine. See "gpapercolor" in PostScript::Graph::Paper. If default_bgnd() is called later, it fills all colours marked thus with a background colour now known.

outer_dashes

If this is unset, inner lines alternate with the outer colour. To get a dashed line, this should be the same value as inner_dashes. (Default: "[]")

Only available for lines.

outer_width

Total width of the line or point, including the border (which may be invisible, depending on colour). The edge is only visible if this is at least 0.5 greater than inner_width. 2 or 3 times inner_width is often best. (Default: 1.5)

When using the circle point shape, this should be quite small to allow the line to be visible inside the circle.

shape

This string specifies the built-in shape to use for points. Suitable values are:

    north   south   east    west
    plus    cross   dot     circle
    square  diamond  

(Default: "dot")

Only available for points.

size

Width across the inner part of a point shape. (Default: 5)

Not available for lines.

width

Set the inner line width. The outer width is also set to twice this value.

x_offset

Move the active position of a point from the centre to somewhere else. Useful for arrows.

Example

By default, a left-pointing arrow will be drawn centrally over the specified point. However, specifying an x_offset of 0.75 the size, it will now be drawn with the arrow tip at the point instead (the left edge of the icon). In practice, making the offset a little larger allows for the unbevelled point which becomes quite pronounced as the line width increases.

    point => {
        shape    => 'east',
        size     => 6,
        x_offset => -6,
    }

y_offset

Move the active position of a point from the centre to somewhere else. Useful for arrows.

Example

By default, an up-pointing arrow will be drawn centrally over the specified point. However, specifying an y_offset of 0.75 the size, it will now be drawn with the arrow tip at the point instead (the top edge of the icon).

    point => {
        shape    => 'north',
        size     => 6,
        y_offset => 6,
    }

OBJECT METHODS ^

write( ps )

Write style settings to the PostScript::File object. This is a convenient way of setting all the postscript variables at the same time as it calls each of the line, point and bar variants below.

All of the postscript variables are set if the constructor option changes_only was set to 0. Otherwise, only those values that are different from the previous style are written out.

See "POSTSCRIPT CODE" for a list of the variables set.

background( grey | arrayref [, same] )

The default outer colour setting (-1) is interpreted as 'use complement to graphpaper background'. Of course, it is not possible to bind that until the graphpaper object exists. Calling this function sets all outer colour values to be a complement of the colour given, unless same is set to non-zero. If not given, same takes on the value given to the constuctor or 0 by default.

use_line

Return 1 if line settings are used.

use_point

Return 1 if point settings are used.

use_bar

Return 1 if bar settings are used.

POSTSCRIPT CODE ^

PostScript variables

These are set within the 'gstyledict' dictionary. All ...color variables are either a decimal or an array holding red, green and blue values. They are best passed to "gpapercolor" in PostScript::Graph::Paper.

    PostScript  Perl method
    ==========  ===========
    locolor     line_outer_color
    lowidth     line_outer_width
    lostyle     line_outer_dashes
    licolor     line_inner_color
    liwidth     line_inner_width
    listyle     line_inner_dashes
 
    ppshape     point_shape
    ppsize      point_size
    pocolor     point_outer_color
    powidth     point_outer_width
    picolor     point_inner_color
    piwidth     point_inner_width
    
    bocolor     bar_outer_color
    bowidth     bar_outer_width
    bicolor     bar_inner_color
    biwidth     bar_inner_width

Setting Styles

Once write has been called to update the postscript variables, the graphic environment must be set to use them. The GraphStyle resource provides a number of functions for this.

line_inner

Sets the colour, width and dash pattern for a line.

line_outer

Sets the colour, width and dash pattern for a line's edge.

point_inner

Sets the colour and width for a point.

point_outer

Sets the colour and width for a point's edge.

bar_inner

Sets the colour and width for a bar.

bar_outer

Sets the colour and width for a bar's edge.

Drawing Functions

The functions which draw the shapes all remove 'x y' from the stack. They use a variable 'ppsize' which should be the total width of the shape, although the elongated shapes are 1.5 times this on the longer side.

    make_plus       make_north
    make_cross      make_south
    make_dot        make_east
    make_circle     make_west
    make_square
    make_diamond

ps_functions

This class function provides the PostScript dictionary gstyledict and code defining the specialist Style functions.

BUGS ^

Please report any you find to the author.

AUTHOR ^

Chris Willmot, chris@willmot.org.uk

SEE ALSO ^

PostScript::File, PostScript::Graph::Paper and PostScript::Graph::Key for the other modules in this suite.

PostScript::Graph::Bar, PostScript::Graph::XY and Finance::Shares::Chart for modules that use this one.

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