Create and use images with MetaPost

MetaPost is a programming language that can be used to create graphics. For example, one creates from the following program code:

beginfig(1)
    for a=0 upto 9:
      draw (0,0){dir 45}..{dir -10a}(6cm,0);
    endfor
endfig;

this graphic:

mp first

MetaPost and the speedata Publisher

The idea now is to be able to use these images in the speedata Publisher as well. To do this, you first define a graphic and then use it later in the box command:

<Layout
    xmlns="urn:speedata.de:2009/publisher/en"
    xmlns:sd="urn:speedata:2009/publisher/functions/en">

    <!-- no beginfig() ... endfig necessary -->
    <DefineGraphic name="dottedbox">
      pickup pencircle scaled 1mm;
      draw (0,0) -- (box.width,0) -- (box.width, box.height) --
        (box.width, box.height) -- (0, box.height ) -- cycle
        dashed withdots withcolor 0.7red ;
    </DefineGraphic>

    <!-- same, but uses predefined path box: -->
    <DefineGraphic name="dottedboxsimple">
        pickup pencircle scaled 1mm;
        draw box dashed withdots withcolor 0.7red ;
    </DefineGraphic>


    <Record element="data">
        <PlaceObject row="1" column="1">
            <Box height="2" width="5" graphic="dottedbox" />
        </PlaceObject>
    </Record>
</Layout>

The width of the box and the height of the box are defined with the variables box.width and box.height in MetaPost. This allows you to adjust the graphic to the defaults in the Publisher.

mp dotted
The dotted lines correspond to the specifications of the box. Raster display has been turned on to make this visible.

Coordinates

The origin of the coordinate system is in the lower left corner of the box, so positive values go in the right and up direction.

Variables

Variables for MetaPost can be set with <SetVariable>.

<SetVariable
    variable="curcol"
    type="mp:rgbcolor"
    select="'colors_mycolor'"/>

The assignment is evaluated at the beginning of the MetaPost context. Thus curcol is available at the beginning of the graphics.

Predefined values

  • All colors defined in the layout can be used in MetaPost with the prefix colors.: 
    <DefineColor name="mycolor" value="#FF4E00"/>

<DefineGraphic name="dots">
    pickup pencircle scaled 3mm;
    for i=0 upto 3:
        draw (i * 1cm, i * 1cm) withcolor colors.mycolor ;
    endfor;
</DefineGraphic>

<Record element="data">
    <PlaceObject row="1" column="1">
        <Box height="5" width="1" graphic="dots" />
    </PlaceObject>
</Record>
  • CSS level 3 colors are defined in RGB colorspace.
  • The width and height of a box can be accessed via box.width and box.height
  • The box' path is saved in the variable box (see the example above).
  • Hans Hagen’s MetaFun macro package is included (parts of it).
  • In page types you can also access these variables:
    Variable Description
    page.width Page width
    page.height Page height
    page.margin.left Margin left
    page.margin.right Margin right
    page.margin.top Margin top
    page.margin.bottom Margin bottom
    page.trim Bleed

Text in MetaPost

sptext("Hello, world!","text","regular")

The arguments are: the text for output, the font family and the variant. The possible values for the variant are: regular, bold, italic and bolditalic.

Example usage with label:

label.top(sptext("origin","text","regular"),(0,0));

Alternatively to the verbose macro there is the short form:

defaultfontfamily := "mptext";
defaultfontstyle := "bold";

draw txt("Hello, world!");

Renders the text in the font family mptext and the variant bold.

Transparency

To get a transparency effect you can supplement a color with the keyword withalpha and a factor. This factor is between 0 (invisible) und 1 (full color).

fill box scaled 0.5 shifted (-20,-20);
fill box withcolor rebeccapurple withalpha 0.6;

MetaPost macros

The macros contained in the “plain” format are included in the speedata Publisher. In addition, the following (partly from MetaFun).

Verschiebungen etc.

xshifted, yshifted

Movement in one direction.

draw unitsquare xshifted 3cm;
xyscaled

Scaling with different values for x and y.

draw unitsquare xyscaled (2cm,5cm);
randomshifted

Shift with random values.

draw unitsquare randomshifted (2cm,5cm);
superellipsed

Transformation to a “superellipse”.

draw box superellipsed 0.9;
roundedsquare

Rectangle with rounded corners.

draw roundedsquare(box.width,box.height,.25cm);
withalpha

Change color intensity (1.0 = full color, 0 = no color).

fill unitsquare withalpha 0.7;
randomized

Randomize the values. A value can be path, a pair or a color.

draw box randomized 2cm;

Paths

box

Rectangle from the layout with the provided width and height.

draw box;

Image commands

drawdot

Draw a dot at a given position.

drawdot origin;
spcolor

Gets a color from the previously defined colors. Can only be used with withcolor. The difference to using a color from the colors. variable is that the color space is preserved and not converted to RGB.

fill box withcolor spcolor("mycolor");

Text

sptext

Text with information about the font and the variant. The possible values are described under defaultfontfamily and defaultfontstyle.

draw sptext("Hello","text","bold");
txt

Text that uses the defaults defaultfontfamily and defaultfontstyle.

Options

defaultfontfamily

Font family which will be used with txt(). The family must have been previously defined in the layout.

defaultfontstyle

Font style used with txt(). Possible styles: regular, bold, italic, bolditalic.

MetaPost resources

There are a number of manuals and tutorials for MetaPost: