The Processing Of Complex Graphic Object Of AutoCAD Based On DWGdirect

While carrying on the operation of opening DWG figure file, if we can preview the figure in File Dialog, then we Can get some figure information of the file before opening the file, and Judge whether this file is the file we need to open according to the information received, and Raise the efficiency well.Nowadays information security has been paid attention by more and more people, Numerous CAD softwares successively offered the file encryption function to ensure users' information security.In unfavorable case of AutoCAD nearly monopolizes CAD software market of our country, the success of several domestic famous CAD softwares has reflected an irrefutable fact: A competitive software, not only should have a strong function, competitive price, but also needs a reliable and compatible interface with AutoCAD.In order to develop engineering drawing software with perfect function, high efficiency and reliability, and accords with the design habit of our engineers, this paper implements the function of figure previewing of DWG file, DWG file encryption, conversion of block and dimension in JHCAD system, which is developed in Visual C++ environment on Windows platform, using object-oriented method, DWGdirect class library.Tasks accomplished are as follows:Through further investigating and analysis of internal structure of DWG figure file and DWGdirect, on the basis of understanding BMP and WMF picture formats, realizes the generation and display of DWG file preview. Making use of the function interfaces offered by DWGdirect, accomplishes encryption and decryption of DWG figure file by calling encryption application program interfaces (CryptoAPI) provided by Microsoft. By means of Characteristic analysis of block and dimension, through studying on solid model of JHCAD and DWGdirect, ensure information integrality of block and dimension while saving the figure in JHCAD as DWG file.The programs have been verified correct and feasible through coding, debugging and testing on JHCAD engineering drawing software platform.