The method was developed to (1) simplify the design process of vector-based complex symbols; (2) promote the sharing and reuse of map symbols, and (3) improve the efficiency of online interactive symbolization.
Symbolization methods are slightly different for point, line, and polygon feature types.
In interactive symbolization, the symbol ID can be acquired by clicking the symbol list on the web page.
The symbolization of line features follows a slightly different process than does point feature symbolization.
The bitmap data are used as a parameter of lineBitmapStyle(), and then, drawing line with line API functions completes the line symbolization.
The symbolization of a polygon is divided into two parts: border styles and fill patterns.
Interactive symbolization is in high demand, especially by web users interested in thematic mapping.
In interactive point symbolization, point symbols available in the library are listed in advance.
We propose a simple mask-based approach to enhance the drawing efficiency and interactivity of polygon symbolization. A mask is an object that limits the visibility of another object to the shape of the mask applied to it.
Figure 5 illustrates the basic steps of the mask-based approach used in polygon symbolization. First, the coordinates of a bounding rectangle are calculated using the getBounds() or getRect() functions in ActionScript.
The bitmap data are then used as a parameter of beginBitmapFill(), which completes the rectangle symbolization. By applying a mask to the rectangle, we produce a symbolized polygon.
The case study shows that our method is fast and user friendly and that it can improve the efficiency of online interactive symbolization. The method based on graphic entity meets the demands of mapping geological disaster information.
