The Classified Design And Implementation Of Chart Symbol Library Based On GDI+

The ocean as an important community resource and transport route, can not onlyprovide a wealth of resource for mankind, but also play the important role inpromoting cultural communication and economic development between countries.Butwith the increase of population, accelerated depletion of land resource andincreasing deterioration of the environment, human beings have to get moreresources from the ocean to sustain their survival and development.However, forall the marine activities, such as sailing, resource exploration and marineengineering construction need to provide a detailed map of the ocean through themarine surveying and mapping.At present,symbols of the electronic chart symbollibrary are not complete unable to meet the growing demand for marine with its lowaccuracy and poor portability.Based on this,this article proposes the idea ofobject-oriented to develop the chart symbol library from the bottom to meet theelectronic chart scale of 1: 50000 display and output requirements.This article applies the method of classification to design the symbols combinedthe GDI+ graphics interface on the platform of Visual C++ 6.0.The set of chartsymbol library is divided into the following three parts:First,the chart symbol libraryis divided into point symbols, line symbols, area symbols and text note four categoriesaccording to the representation of geographical elements and geometriccharacteristics of the symbols,and then introduce the related conceptions of pointlocation and line location.Second,for point symbols,this paper proposes an idea basedon the combining of the rule primitives to implement them. This method simplifiesthe drawing information of the point symbols;for line symbols, the paper will bedivided into simple and complex types to draw respectively.To achieve the simple linesymbols,the paper will use the method based on layered overlay and the complex linesymbols are proposed to realize on bases of horizontal loop configuration;for areasymbols,the means of drawing are divided into this flowing four kinds in this paper:area symbols based on the color-filled,area symbols based on GDI +template-filled,area symbols based on line-filled and area symbols based on linefill;for the text annotation,this article calls the Draw String function of GDI+ to realizeaccording to the font type,font style,font size,and font color.Third, use the method ofparametric to transfer data and then introduce the process of code implementationof each kind of chart symbol.Through the above methods, this paper has completed the establishment of chartsymbol library basically,but when the user draws some complex line symbols,therewill appear discontinuous problem at the corner.The researcher advises a waycombined the affine transformation and horizontal loop configuration fillingalgorithm to solve it.The paper achieves the drawing of the complex line symbols andsolve the problem of discontinuity at the corner very well by calculating the angle ofrotation,making coordinate rotation and affine transformation.