Lines and Line Styles

Settings in the format toolbar control the appearance of lines. The format toolbar settings apply to all lines in a given drawing. The size parameter sets the thickness of the line in printer's points, the same unit of measure used for font sizes. One printer's point is 1/72 inch.

 

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By default, lines are shown in a solid line of size 1 with black foreground color. The illustration shows a map with a layer containing lines positioned above a layer containing the background areas.

 

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We can change the line style by clicking on the Style button for lines and choosing a different style.

 

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A dotted style shows alternating foreground and background color. Because the background color used is the same color as that used for the areas, the line appears as a dotted line of foreground color.

 

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We can change the background color to white to show the alternating color effect of this line style.

 

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When size is increased in dotted line styles, only the thickness of the background color is increased. This provides a vivid effect.

 

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If we use the Layers pane to turn on some other layers in the sample map, we can see how the vivid style helps these lines stand out from other lines. The format toolbar illustration shows the formatting for the blue lines in one of the other layers, a "hydrography" layer showing water features such as streams and lakes.

 

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In this illustration we have increased the size of the dotted lines to 5 to give them a thicker appearance. We have also "toned down" the brightness of the lines by changing the opacity of the layer hosting them to 50%. See Layer Opacity for information on changing the transparency/opacity of layers. Making the layer partially opaque allows some of the blue lines behind the dotted line layer to show through. Clever use of opacity will often allow complex maps to be more legible.

 

images\sc_line_styles_07.gif

 

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In the illustration above we have changed the style back to a solid line, we've changed the size to 3 and we've changed the foreground color to yellow. Solid styles that are "all foreground" will increase the thickness of the foreground color as well.

 

Directed Line Styles

 

Some line styles are asymmetric in that their appearance depends on the direction of the line. All lines in Manifold have a "direction" that is implied by the order in which they are drawn from the first coordinate that defines the line to the last.

 

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A triangle line style is one such style. When looking along the direction of the line from the beginning to the end the triangles point to the left in this style. This can be seen by drawing a line.

 

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We can use this style with the Insert Line tool to draw a new line by clicking at the left and then clicking at the right in the direction shown by the red arrow.

 

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The result is a line drawn in triangles with the triangles pointing to the left along the direction of the line.

 

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Suppose we draw a second line in the opposite direction as indicated by the red arrow.

 

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In this case, the triangles will point in the opposite direction.

 

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We can see that the orientation of the lines depends upon their direction, as shown by the red arrows. To switch the direction of a line (and thus the orientation of any asymmetric line style) select the line and use the Reverse Lines transform toolbar operator.

 

Lines with Arrowheads

 

Manifold includes directed line styles that have arrowheads. The arrowheads are placed at the end of a line.

 

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In the example above four lines are drawn using directed line styles with arrowheads. The lines are drawn in a map above a layer containing points.

 

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Line styles can be combined with other line styles in a map. The illustration above shows a line that was copied from one drawing and pasted into another drawing. Both drawings were shown together in a map. The upper drawing formats the line using a series of arrowheads for the line with the same yellow color for foreground and background. The lower drawing formats the line as a single thick black line.

 

Antialiasing

 

Antialiasing is a computer technology used to make lines appear smoother and less jagged.

 

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Without antialiasing lines are drawn using pixels where each pixel is either turned on in the color used by the line or it is turned off. The result is a jagged line appearance for some lines.

 

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Seen in detail, the jagged appearance arises from the stair-step nature of lines drawn at some angles for which transitions from one pixel to the next must be abrubt.

 

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Antialiasing as seen above provides a smoother appearance to lines.

 

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Antialiasing works by interpolating pixel colors between the color specified for the line and whatever color is visible surrounding the line. In the case of a black line seen against a background of white color antialiasing will use gray scale colors between white and black in addition to the pure black of the line. When seen from afar the use of interpolated colors fools the eye into seeing a smoother line.

 

Manifold can draw lines either with or without antialiasing as specified in the Tools - Options - User Interface options. The default setting uses antialiasing to provide lines with a smoother appearance.

 

Although antialiasing usually provides a better visual effect it does have some drawbacks. Lines will appear slightly thicker with antialiasing and some line styles or lines drawn at certain angles may appear to be unacceptably fuzzy compared to other lines. We may also want to turn antialiasing off before converting a drawing to an image if the touch selection will later be used with the image to select all lines. Touch selection can be used to select pixels that represent a line in an image if the line is not antialiased because all of the pixels in the line will be the same color. Touch selection cannot be used conveniently to select all the pixels that represent a line in the case of antialiased lines because the pixels will be many different colors.

 

Transparent Foreground Color in Lines

 

Choosing a transparent color for foreground color for lines will turn off display of lines. This is a short-cut way of turning off lines in certain effects. This allows a thematic format to be arranged so that line foreground color is transparent with certain values, thus turning off for display any lines with transparent foreground color. For example, if a thematic format is defined that uses the Selection (I) intrinsic field to show foreground color as transparent if a line is not selected and black if a line is selected, then only selected lines will appear.

 

Note

 

The /slist command line option provides a handy way of getting a list of all available formatting styles and their names for use by programmers. See the Command Line Options topic.

 

See Also

 

Creating Bordered Lines

Thematic Formatting