It is often necessary to enable or disable parts of a style sheet, or make them dependent on run-time parameters. While it's possible to solve the problem using several different style sheets, it is much easier to put everything into one style sheet and select different features at run-time using conditional compilation controlled by parameters set by the application.
You can select any part of a style sheet (that is, any balanced XML) using
<if exp="expression"> ... </if>...
Here are two maps of the same area drawn using different style sheets.
Above: Poole in southern England using the standard style sheet....
Dimensions are specified using numbers followed by optional units. A number without a unit refers to pixels. Sometimes units are not allowed, as for example in opacity levels, which are dimensionless. Where units are allowed, you can use any of the following:
- pt: printer's points of exactly 1/72in (sometimes called PostScript points).
- pc: printer's picas of 12pt.
- cm: centimeters.
- mm: millimeters.
- in: inches.
- m: map meters; that is, meters at the scale of the map, converted to pixels using the current map projection.
- %: a percentage of some value depending on context; for example, in the context of a road, percentages refer to the width of the road, allowing you to specify that a road name is 75% of the width of the road.
Dimensions can optionally be followed by limits: minimum and maximum values. For example, it is useful to specify a label size in map meters, but clamp it to a certain range of sizes, avoiding lettering that is too small to read, or so large as to be ugly and obtrusive. For example:
sets a label size to 300 map meters but clamps it to the range 8pt...24pt. It is legal to omit the third (upper) limit, as in:
Colors are RGBA (red, green and blue components plus an 'alpha' or opacity level), and can be specified in these ways:
- Hexadecimal 24-bit RGB, in the form #RRGGBB, where each group of two hex digits is an 8-bit intensity value. An opacity value of 255 (fully opaque) is used.
- Hexadecial 24-bit RGB using three digits only: #RGB; the digits are treated as #RRGGBB
- Hexadecimal 32-bit RGBA, in the form #RRGGBBAA, where the first three groups of two hex digits are the red, green and blue intensity levels and the last (AA) is the alpha or opacity value, where 0 = transparent and 255 = opaque.
- Hexadecimal 32-bit RGBA using four digits only: #RGBA; the digits are treated as #RRGGBBAA
- As an SVG color keyword. SVG (the W3 Scalable Vector Graphics standard) defines over a hundred keywords for colors, including all the common names and many unusual ones like 'khaki' and 'teal'.
Fonts are specified using a subset of the CSS font style attributes. For details see Labels....
Labels in style sheets
The <label> section in a <layer> section tells CartoType to draw a label and defines its style, including font attributes.
You can have up to two <label> sections in a <layer>. That enables you to draw both a highway shield with the highway reference, and an ordinary name along the road, for example. Use <labelAttrib> to select the correct name for each label, if using more than one.
The <label> attributes, in alphabetic order, are:...
<scale> and <zoom> sections in style sheets
You will nearly always want your maps to look different at different scales. Some objects will not appear at some scales, and other will be drawn very differently. For example, minor roads may not appear at small scales, and city names may be suppressed or drawn as a faint overlay at large scales.
The easiest way to make this happen is to use <scale> sections:
<scale min='m' max='n'> ... </scale>
with any balanced XML you like inside them....
Levels of map objects
Most mapped objects are at ground level, but often it is useful to distinguish between various vertical levels, to allow the map to display objects in layer order.
CartoType uses 16 different levels. Ground level is 0, lower levels range from -8 (lowest) to -1, and higher levels range from 1 to 7 (highest).
Levels of map objects
How levels are stored in map objects
The level is stored as a signed nybble in bits 12..15 (mask = 0x0000F000) of the integer attributes of an object, but only if the road flag mask for that layer selects those bits. The road flags are set in the <layer> element, either by road='true', which sets them to 0xFFFFFFFF (all ones) or by the roadflags attribute: for example, roadflags='#1F001' in the amenity <layer> states that we wish to use the 'bridge' (0x10000), 'level' (0xF000) and 'tunnel' flags (0x1)....
You can create CartoType maps (CTM1 files) containing array objects. These are effectively textures in computer graphics terms: that is, they are rectangular bitmaps which can be projected on to the map and rendered in various ways.
The most common standard layers created in CTM1 files by the tool generate_map_data_type1 are called terrain-shadow and terrain-height-feet.
Terrain shading using the terrain-shadow layer
The terrain-shadow layer contains an eight-bit opacity (alpha) value for each sample, representing the light intensity for a simulated sun in the south-west. You draw it like this, giving a color value to be used when drawing the shadow. You can provide an opacity value as well. For example:
<layer name='terrain-shadow'> <shape fill='#446' opacity='0.75'/> </layer>
gives light greyish-green terrain shading....
The <defs> section
Objects used more than once can be defined in a <defs> section. An objects must be defined before any layers in which it is used. The following types of objects can be defined in the <defs> section: macros, hachures, icons, patterns and strings.
Macros define named sections of a style sheet for re-use multiple times (full description here).
The hachure used in the example to the right is specified like this:
<hachure id="other-area-shading" width="1pt" interval="4pt" color="brown" opacity="0.4"/>...
The <layer> section
A layer is a named set of map objects of a common type, like roads, parks, or stations. Layers are drawn in the order in which
- name: the name of the layer, which must match the name stored in the map data file or database
- road: if 'true' or 'yes', this is a road layer. Setting the road attribute allows layers to be drawn in appropriate order: roads, including tunnels, are drawn after (on top of) objects in earlier layers.
Displaying highlighted routes, pushpins, user-created data and other auxiliary data
CartoType applications that do navigation or route-finding need to highlight the current route, display points of interest and addresses selected by the user, and draw other temporary, fast-changing or custom data.
You can do this in a completely flexible way using an auxiliary map database supplied to CartoType at map drawing time. For example, to highlight a route, you could create a memory-resident map database (using the class CMemoryMapDataBase), add the layer "route" to it, and arrange for this database to contain one or more line objects representing the current route, if any.
You then add a layer section for the "route" layer to the style sheet, in a convenient place: probably after all other ordinary layers but before <labelLayer/>.
When a map is drawn and an auxiliary database is supplied as well as the main database, for every layer in the style sheet both databases are searched for matching objects. Objects from the main database are drawn first, then objects from the auxiliary database....
The <labelLayer> section: a special layer for icons and labels
All icons and labels are collected and drawn as a separate layer, which is drawn when the <labelLayer> section is interpreted. Icons are drawn immediately before labels. The <labelLayer> tag has no attributes, so you just place
in the style sheet, at the same level as other layers. Normally it is the last item in the style sheet.
You can achieve various special effects by using more than one <labelLayer/> tag. Each label layer draws all the icons and labels that have been stored since the last label layer if any. One application for this feature is to draw icons and labels for routing information independently of all others, and overlapping them....
The <shape> element in a <layer> controls the drawing of polygons. The <shape> attributes are
- border: the color used to draw the border; omit this if no border is wanted; if it is specified, but borderWidth is omitted, the border is drawn one pixel wide.
- borderWidth: the width of the border.
- borderOffset: the amount by which the border is inset (if positive) or moved outwards (if negative).
- dashArray: a dashed border can be drawn by supplying a list of numbers giving the lengths of the filled-in sections and the gaps between them, in units of the width of the border (given by the borderWidth attribute). For example, the value '1,2' specifies dashes one unit long and gaps two units long. The list of numbers can be any length.
- fill: the color used to fill the polygon; omit this if the polygon is not to be filled.
- height (legal values are 'yes' and 'no'): if 'yes', any suitable map object attributes are used to draw the building in 3D if required. These attributes are _t (top in meters), _b (bottom in meters) and any attribute starting with _roof:.
- insetBorder (legal values are 'yes' and 'no'): if 'yes', the border is inset by half its width, making it fit inside the polygon.
- opacity: the opacity of both the fill and border colors. To set the fill and border opacity values separately, use the #RRGGBB or #RRGGBBAA form for specifying the colors.
- smooth (legal values are 'yes' and 'no'): if 'yes', the polygon is smoothed.
<shape fill="lightgray" border="darkgray" borderWidth="10m" opacity="0.5"/>
Here is a map using inset borders (insetBorder='yes') for national boundary polygons:
The <line> section in a <layer> controls the drawing of lines, the most important of which are roads. Some attributes apply only to roads. The <line> attributes are
- fill: the color used for the interior of the line
- border: the color of the borders of the line
- centerLine: (for roads only) the color of the center line of a road; used for major divided highways; center lines are drawn only if the road is marked as divided in the data
- width: the width of the line
- borderWidth: the width of the borders; percentage values refer to the width of the line
- centerLineWidth: (for roads only) the width of the center line; percentage values refer to the width of the road
- opacity: the opacity of all features - line, border and center line. To set opacity values separately use the #RRGGBB or #RRGGBBAA form for specifying the colors
- antiAlias: (allowed values: "true" or "false") if true (the default value) use anti-aliasing to draw the line and its border more smoothly.
- dashArray: a dashed line can be drawn by supplying a list of numbers giving the lengths of the filled-in sections and the gaps between them, in units of the width of the line. For example, the value '1,2' specifies dashes one unit long and gaps two units long. The list of numbers can be any length.
The <icon> section in a <layer> controls the drawing of icons for point objects. Icons are specified using SVG (Scalable Vector Graphics). The <icon> attributes are:
- canCombine: if the value is "yes" or "true" multiple instances of this icon are combined (at the time of drawing the map) when too close together. By default icons do not combine. Combined icons are given the attribute _combined=N, where N is the number of original icons combined.
- canOverlap: if the value is "yes" or "true" the icon can overlap other icons. By default icons are not allowed to overlap. Non-overlapping icons are drawn only if they would not overlap other non-overlapping icons. Overlapping icons are always drawn.
- color: if present, overrides the natural color of the icon as defined by the SVG code; the icon is drawn in monochrome, colorising it using the specified color
- colorAttrib: the name of a map object attribute giving the color of the icon; the default map object attribute name is _color. Map objects having the specified attribute use it as the icon color.
- height: height of the icon; when the icon is rendered it is scaled to this height; if width is not set it is calculated automatically, preserving the aspect ratio of the SVG graphics
- hotSpotX: x coordinate of the icon's hot spot, which is the point on the icon to be positioned at the point of interest on the map; defaults to 50% of the icon's width; percentage values refer to the width of the icon
- hotSpotY: y coordinate of the icon's hot spot, which is the point on the icon to be positioned at the point of interest on the map; defaults to 50% of the icon's height; percentage values refer to the height of the icon
- id: the name by which an icon can be referenced elsewhere in the style sheet. Icons can be referenced anywhere after their definition, whether they are defined in a <defs> section or at their point of first use in a layer.
- labelX, labelY: x and y coordinates of the label position, relative to the hotspot, if a label is to be drawn on top of the icon (as in US Highway shields). The label is centered on this position. Percentage values refer to the width and height of the icon. The default values are both 0, meaning that the label is drawn over the hotspot. Percentage values refer to the height of the icon.
- priority: the label priority, with the same meaning as it has in <label>; this attribute allows you to set the label priority if a label consists of an icon only. This attribute works only if it is part of the <icon> element in a <layer>, not if it is specified in the <icon> element in the <defs> section.
- ref: a reference to an icon defined previously in the <defs> section of the style sheet. If a <ref> is present, the <svg> section is taken from the <icon> in the <defs> section.
- refAttrib: the name of a map object attribute containing the icon reference; if this is specified, for any map objects having the attribute, the value of the attribute is used to select the <icon> from the <defs> section
- text: the text for an icon made from a character or characters rather than SVG graphics
- textAttrib: if not empty, the name of a map object attribute giving the icon text, for use with icons consisting of one or more characters. Overrides text.
- width: width of the icon; when the icon is rendered it is scaled to this width; if height is not set it is calculated automatically, preserving the aspect ratio of the SVG graphics
Every <icon> section that does not load a predefined icon using the ref attribute must contain an <svg> section defining the icon using a subset of the Scalable Vector Graphics language. CartoType supports the following SVG graphic elements fully: <g>, <rect>, <circle>, <ellipse>, <line>, <polyline>, <polygon>, and <path>, and partially supports <text>.
Here is a sample <icon> section containing some SVG code to draw a large blue letter H to indicate a hospital:
<icon width='70m,16pt,100pt'> <svg width='80' height='100'> <g stroke='blue' stroke-width='20'> <line x1='10' y1='0' x2='10' y2='100'/> <line x1='70' y1='0' x2='70' y2='100'/> <line x1='10' y1='50' x2='70' y2='50'/> </g> </svg> </icon>...
Graphics can be used to indicate bridges and ramps (roads connecting limited-access roads like motorways to other roads). They consist of an optional shadow under the bridge, and optional lines at the side of the bridge, with user-definable ends.
Bridge graphics are drawn for roads with the bridge attribute, and ramp graphics are drawn for those with the ramp attribute.
The bridge graphics above are drawn using this style:
<bridge width='45m,2pt' border='dimgrey' borderWidth='14%,1' endPath='l 512 512' maxScale='50000'/>
You use the <bridge> or <ramp> tag inside a < layer> tag (or inside a <condition> in a layer). The <bridge> and <ramp> attributes are:
- border: the border color
- shadow: the shadow color
- width: the width of the bridge (distance between bridge borders)
- borderWidth: the width of the border strokes
- shadowWidth: the width of the shadow
- shadowOffsetX: x offset of the shadow, relative to the road
- shadowOffsetY: y offset of the shadow, relative to the road
- maxScale: maximum scale (denominator) at which the bridge graphics are drawn
- endPath: a path, using SVG path syntax, for strokes appended to the ends of the bridge sides. It gives one of the four ends only: that of the top right end, if the bridge is drawn horizontally. The other ends are generated by transforming the path as needed. The path units are 1024ths of the line width unless modified by unitsPerLineWidth.
- unitsPerLineWidth: the size of the units in endPath, defined as the number of units equal to the line width. The default value is 1024
- fill: if present, the fill color for the bridge or ramp; if absent, the bridge or ramp inherits the road color.
- lineBorder: if present, the line border color for the bridge or ramp; if absent, the bridge or ramp inherits the road's border color.
- lineWidth: if present, the line width for the bridge or ramp; if absent, the bridge or ramp inherits the road's line width.
- lineBorderWidth: if present, the line border width for the bridge or ramp; if absent, the bridge or ramp inherits the road's border width.
For all the dimensions, percentages are relative to the width of the road....
Tunnels can be shown by fading the road, drawing it as a dashed line, or both. Graphics can be drawn to show the mouths of the tunnel.
The tunnel named IJ-TUNNEL above shows all three of these methods and is drawn using this style:
<tunnel dashArray='1,1' mouth='dimgrey' mouthWidth='20%,1' mouthPath='m 0 512 a 512 512 0 1 1 0 -1024'/>
You use the <tunnel> tag inside a <layer> tag (or inside a <condition> in a layer). The <tunnel> attributes are:
- fade: a value in the range 0...1: the amount by which the tunnel is faded compared to a surface-level road. 0 is no fading; 1 makes the tunnel disappear.
- fill: the fill color. If this is not specified, the road's ordinary fill color is used.
- border: the border color. If this is not specified, the road's ordinary border color is used.
- dashArray: the dash array if any. If this is not specified the dash array is inherited from the ordinary road style.
- maxScale: maximum scale (denominator) at which the tunnel style is used
- mouthWidth: width of the tunnel mouth symbol; if a percentage is used it is relative to the width of the road. If SVG is used (see below) the width is used as the width and height of the SVG image.
- mouthPaint: paint used for the tunnel mouth symbol
- mouthPath: a path, using SVG path syntax, for graphics drawn at tunnel mouths. It specifies the right hand end, relative to the end of the tunnel. The other end is generated by reflection. The path units are 1024ths of the line width unless modified by unitsPerLineWidth.
- unitsPerLineWidth: the size of the units in endPath, defined as the number of units equal to the line width. The default value is 1024
Using SVG for tunnel graphics
You can use SVG for more complex graphics for tunnel mouths. Do this by embedding an <svg> element inside a <tunne>l element. For example:
<tunnel dashArray='1,1' fill='yellow' mouthWidth='150%' maxScale='25000'> <svg x='-750' y='-750' width='1500' height='1500'> <linearGradient id="tunnel_gradient" gradientUnits="userSpaceOnUse" x1="0" y1="0" x2="-512" y2="0"> <stop offset="0" style="stop-color:cornflowerblue"/> <stop offset="1" style="stop-color:yellow"/> </linearGradient> <path stroke='none' fill="url(#tunnel_gradient)" d='m 0 -500 a 500 500 0 1 0 0 1000 z'/> <path stroke='brown' fill='none' stroke-width='60' d='m 0 -500 a 500 500 0 1 0 0 1000'/> </svg> </tunnel>
which gives this:
In this example the SVG view rectangle is 1500 units wide, centered on (0,0). The rectangle has to be big enough for the graphics to be rotated to any angle without being clipped off. The width of the SVG rectangle is scaled to the width given by mouthWidth, so 1500 units are scaled to 150% of the line width - therefore 1000 SVG units correspond to the width of the line. The graphics are drawn relative to the right hand end of the tunnel, with (0,0) at the end itself, and the x axis aligned to the direction of the tunnel....
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