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Andreas Kohlbecker, 12/02/2008 04:58 PM


Wild and tame ideas for the EDIT Map REST Service API

Area Styles

Andreas Kohlbecker - 27.10.2008, 03.11.2008

I would prefer a more generic syntax for specifying area styles. First of all I'd like to explain why I think that the Geo REST Service would benefit from a more generic syntax.

Let's assume a situation in which a map should express different kind of information, e.g. distribution, soil characteristics, etc.. In this case one would likely want to express the different kind of information by

a) the polygon border style by b) the fill colour of the polygon, c) by a pattern drawn a foreground of the polygon. So we would have to handle arbitrary combinations of the different styles.

Now if we define the polygon border style, fill colour and the color and pattern drawn in the foreground together in on area style attribute, we would have to define every combination of these individually. This would not only bloat up the style definition but would also bloat up the legend by requiring a for each style combination thus introducing redundancy. Therefore I recommend splitting the definitions for

  • polygon border style

  • background fill colour

  • foreground color and pattern

The API proposal already is designed that way:

  (area style) as=<area style id>:<color>[,<style_label>]|..              -  defines a background (fill) color for a shape

               as=<area style id>:<pattern id><color>[,<style_label>]|.. -  defines a pattern and foreground color to fill a shape with

You can define separate area styles for background and foreground and you can apply arbitrary combinations of these to an area:

(area data) ad=<layer name>:<area style ids>:<area id>,..|<area style ids>:<area id>,..||<layer name>:<area style ids>:<area id>,..|
<area style ids> is a string of one letter [a-z,A-Z] area style ids

The polygon border style however is missing in the API, but we have the

(layer style) ls=<layer_style_id>:[<line_color>][,<line_width>][,<stroke_style_id>]|..

Which is nothing else but a polygon border style applied to all polygons defined in one layer. Maybe we should rename layer style into area border style ?

And split area style into area background style and area foreground style then we would have the following attributes:

(area background  style) abs=<area style id>:<color>[,<style_label>]|..              -  defines a background (fill) color for a shape

(area foreground style)  afs=<area style id>:<pattern id><color>[,<style_label>]|.. -  defines a pattern and foreground color to fill a shape with

(area polygone style)    aps=<area style id>:[<line_color>][,<line_width>][,<stroke_style_id>][,<style_label>]|.

The in the currently proposed syntax does not allow using named colors, otherwise the attribute values can not be parsed, so I am using the rgb hex values here

abs=a:aaaaaa|b:ffff00

aps=c:0000ff,dotted,4|d:0000ff,no-dotted,10| e:00ff00,no-dotted,10

area border styles would be also applicable to layers:

(layer) l=<layer name>[:[<area style id>][,<shp file url>][,<raster data url>]]|...

The layer attribute only would accept s which actually are area border styles .

The the currently proposed syntax does not allow using named colors, otherwise the attribute values can not be parsed, so I am using the rgb hex values here

abs=a:aaaaaa|b:ffff00
aps=c:0000ff,dotted,4|d:0000ff,no-dotted,10| e:00ff00,no-dotted,10

Now lets take the styles from your example and express them by combinations of a, b, c, d, e

grey,blue,4,dotted = ac
grey,blue,10,no-dotted = ad
yellow,green,10-no-dotted = be

So you would use these combinations of area styles in

(area data) ad=<layer name>:<area style ids>:<area id>,..|

The advantage I see in this approach are the better legends you can create eg:

abs=a:aaaaaa,arid|b:ffff00,semiarid
aps=c:0000ff,dotted,4,native|d:0000ff,no-dotted,10,cultivated| e:00ff00,no-dotted,10, abandoned

would result in a legend like which explains all possible combinations without the need to explicitly mentioning every one:

[  ] : arid
[  ] : semiarid
[  ] : native
[  ] : cultivated
[  ] : abandoned

Updated by Andreas Kohlbecker about 14 years ago · 4 revisions