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CadLib for creating DXF(Drawing Interchange Format) filesBy Omid ShahabiA link-library and its interface class to create, load and modify DXF files. |
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Drawing Interchange Format (DXF) files enable the interchange of drawings between AutoCAD and other programs. DXF files can be either ASCII or binary formats. Because ASCII DXF files are more common than the binary format, CadLib uses ASCII DXF format.
The CadLib is not a Computer Aided Design (CAD) program. It is a tool for creating DXF files that are used in the CAD programs. It consists of two parts. One of them is a Dynamic Link Library to create the DXF file. The other part is the programming interface. It is a class that integrates the cadio.dll functions. It can be used in Microsoft Visual C++ projects. In addition, the cadio.dll can be used in other Win32 programs.
In some programs, it is needed to create a drawing output for use in other programs such as AutoCad. For example, in a "Building Detail Sheet Generator Program", the program needs to create a drawing output. And the most standard format for communicating drawing data is DXF.
The DXF format is a tagged data representation of all the information contained in a drawing file. Tagged data means that each data element in the file is preceded by an integer number that is called a group code. A group code's value indicates what type of data element follows. This value also indicates the meaning of a data element for a given object (or record) type. Virtually all user-specified information in a drawing file can be represented in DXF format. (from AutoCad's DXF reference)
A DXF file consists of some sections. Each section has some drawing data in itself. The CadLib uses the following sections:
The main reference for DXF file structure that is used for CadLib is the AutoCad's DXF reference. You can find more information about DXF file structure here.
The classes are interfaces between CadIO.dll and the main program.
"Test" has come with CadLib to demonstrate how to generate a DXF file with
CDxfFileWrite and CDrawing classes.
CDxfFileWrite gathers all the commands needed to directly create
a DXF file. Usage of CDxfFileWrite is as follows:
CDxfFileWrite dxffile; dxffile.Create( "d:\\test.dxf" );
// Header Section ------------------------------------------ dxffile.BeginSection(SEC_HEADER); dxffile.EndSection(); // close HEADER section ------------------------------------
// Tables Section ------------------------------------------ dxffile.BeginSection(SEC_TABLES); // LTYPE table type ------------------------- dxffile.BeginTableType(TAB_LTYPE); DXFLTYPE ltype; double elem[4]; // Continuous ZeroMemory(<ype, sizeof(ltype)); ltype.Name = "Continuous"; ltype.DescriptiveText = "Solid line"; dxffile.AddLinetype(<ype); // DASHDOT2 ZeroMemory(<ype, sizeof(ltype)); ltype.Name = "DASHDOT2"; ltype.DescriptiveText = "Dash dot (.5x) _._._._._._._._._._._._._._._."; ltype.ElementsNumber = 4; ltype.TotalPatternLength = 0.5; ltype.Elements = elem; elem[0] = 0.25; elem[1] = -0.125; elem[2] = 0.0; elem[3] = -0.125; dxffile.AddLinetype(<ype); dxffile.EndTableType(); // close LTYPE table type ------------------- // LAYER table type ------------------------- result &= dxffile.BeginTableType(TAB_LAYER); result &= dxffile.AddLayer("Layer1", 1, "Continuous"); result &= dxffile.AddLayer("Layer2", 2, "Continuous"); result &= dxffile.AddLayer("Layer3", 3, "Continuous"); result &= dxffile.AddLayer("Layer4", 4, "Continuous"); result &= dxffile.EndTableType(); // close LAYER table type ------------------- // STYLE table type ------------------------- dxffile.BeginTableType(TAB_STYLE); DXFSTYLE tstyle; ZeroMemory(&tstyle, sizeof(tstyle)); tstyle.Name = "Style1"; tstyle.PrimaryFontFilename = "TIMES.TTF"; tstyle.Height = 0.3; tstyle.WidthFactor = 1; dxffile.AddTextStyle(&tstyle); dxffile.EndTableType(); // close STYLE table type ------------------- // DIMSTYLE table type ---------------------- dxffile.BeginTableType(TAB_DIMSTYLE); DXFDIMSTYLE dimstyle; // DIM1 ZeroMemory(&dimstyle, sizeof(dimstyle)); dimstyle.Name = "DIM1"; // DimStyle Name dimstyle.DIMCLRD = 2; // Dimension line & Arrow heads color dimstyle.DIMDLE = 0.0000; // Dimension line size after Extensionline dimstyle.DIMCLRE = 2; // Extension line color dimstyle.DIMEXE = 0.1800; // Extension line size after Dimline dimstyle.DIMEXO = 0.0625; // Offset from origin dimstyle.DIMBLK1 = "ClosedFilled";// 1st Arrow head dimstyle.DIMBLK2 = "ClosedFilled";// 2nd Arrow head dimstyle.DIMASZ = 0.1800; // Arrow size dimstyle.DIMTXSTY = "Style1"; // Text style dimstyle.DIMCLRT = 3; // Text color dimstyle.DIMTXT = 0.1800; // Text height dimstyle.DIMTAD = 1; // Vertical Text Placement dimstyle.DIMGAP = 0.0900; // Offset from dimension line dxffile.AddDimStyle(&dimstyle); dxffile.EndTableType(); // close DIMSTYLE table type ---------------- dxffile.EndSection(); // close TABLES section ------------------------------------
// Entities Section ------------------------------------------ dxffile.BeginSection(SEC_ENTITIES); // set current layer to Layer2 dxffile.SetCurrentLayer("Layer2"); // draw a line dxffile.Line(1.2, 3.3, 7.5, 7.7); // draw a circle dxffile.Circle(7.8, 4.3, 1.75); // set current layer to Layer4 dxffile.SetCurrentLayer("Layer4"); // draw a solid REALPOINT points[4]; points[0].x = 10.4; points[0].y = 7.2; points[1].x = 13.6; points[1].y = 7.4; points[2].x = 13.1; points[2].y = 4.9; points[3].x = 10.9; points[3].y = 5.9; Solid(4, points); // set current textstyle to Style1 dxffile.SetCurrentTextStyle("Style1"); // draw text dxffile.Text("Sample Text", 5.9, 6.7, 0.3, 35); // draw a dimension line dxffile.SetCurrentDimStyle("DIM1"); dxffile.DimLinear(6.05, 3, 9.55, 3, 9.55, 2, 0, "3.50"); dxffile.EndSection(); // close ENTITIES section ----------------------------------
dxffile.Close();
CDrawing class has all the commands to create a drawing in
memory and save it as a DXF file. Usage of CDrawing is as
follows:
CDrawing drw; drw.Create( );
// Tables Section ------------------------------------------ // LTYPE table type ------------------------- LTYPE ltype; OBJHANDLE objhandle1; // Continuous ZeroMemory(<ype, sizeof(ltype)); strcpy(ltype.Name, "Continuous"); strcpy(ltype.DescriptiveText, "Solid line"); objhandle1 = drw.AddLinetype(<ype); // DASHDOT2 ZeroMemory(<ype, sizeof(ltype)); strcpy(ltype.Name, "DASHDOT2"); strcpy(ltype.DescriptiveText, "Dash dot (.5x) _._._._._._._._._._._._._._._."); ltype.ElementsNumber = 4; ltype.PatternLength = 0.5; ltype.Elements[0] = 0.25; ltype.Elements[1] = -0.125; ltype.Elements[2] = 0.0; ltype.Elements[3] = -0.125; drw.AddLinetype(<ype); // LAYER table type ------------------------- LAYER layer; // Layer1 ZeroMemory(&layer, sizeof(layer)); strcpy(layer.Name, "Layer1"); layer.Color = 1; layer.LineTypeObjhandle = objhandle1; // Continuous drw.AddLayer(&layer); // Layer2 ZeroMemory(&layer, sizeof(layer)); strcpy(layer.Name, "Layer2"); layer.Color = 2; layer.LineTypeObjhandle = objhandle1; // Continuous drw.AddLayer(&layer); // STYLE table type ------------------------- STYLE style; ZeroMemory(&style, sizeof(style)); strcpy(style.Name, "Style1"); strcpy(style.PrimaryFontFilename, "TIMES.TTF"); style.LastHeightUsed = 0.3; style.WidthFactor = 1; objhandle1 = drw.AddTextStyle(&style); // DIMSTYLE table type ---------------------- DIMSTYLE dimstyle; // DIM1 ZeroMemory(&dimstyle, sizeof(dimstyle)); strcpy(dimstyle.Name, "DIM1"); // DimStyle Name dimstyle.dimclrd = 2; // Dimension line & Arrow heads color dimstyle.dimdle = 0.0000; // Dimension line size after Extensionline dimstyle.dimclre = 2; // Extension line color dimstyle.dimexe = 0.1800; // Extension line size after Dimline dimstyle.dimexo = 0.0625; // Offset from origin strcpy(dimstyle.dimblk1, "ClosedFilled");// 1st Arrow head strcpy(dimstyle.dimblk2, "ClosedFilled");// 2nd Arrow head dimstyle.dimasz = 0.1800; // Arrow size dimstyle.dimtxstyObjhandle = objhandle1;// Text style dimstyle.dimclrt = 3; // Text color dimstyle.dimtxt = 0.1800; // Text height dimstyle.dimtad = 1; // Vertical Text Placement dimstyle.dimgap = 0.0900; // Offset from dimension line drw.AddDimStyle(&dimstyle);
// Entities Section ------------------------------------------ // set current layer to Layer2 drw.SetLayer("Layer2"); // draw a line drw.Line(1.2, 3.3, 7.5, 7.7); // draw a circle drw.Circle(7.8, 4.3, 1.75); // set current layer to Layer1 drw.SetLayer("Layer1"); // draw a solid REALPOINT points[4]; points[0].x = 10.4; points[0].y = 7.2; points[1].x = 13.6; points[1].y = 7.4; points[2].x = 13.1; points[2].y = 4.9; points[3].x = 10.9; points[3].y = 5.9; drw.Solid(points[0], points[1], points[2], points[3]); // set current textstyle to Style1 drw.SetTextStyle("Style1"); // draw text drw.Text("Sample Text", 5.9, 6.7, 0.3, 35); // draw a dimension line drw.SetDimStyle("DIM1"); drw.DimLinear(6.05, 3, 9.55, 3, 9.55, 2, 0, "3.50");
drw.SaveDXFFile(DxfFileName);
CDrawing and free allocated memory. drw.Destroy();
CDrawing drw; drw.Create( );
LoadDXFFile member function to load DXF file into memory. drw.LoadDXFFile("Sample.dxf");
That's all!
Since I am a Civil Engineer, I decided to write a program to generate a beam or columns detail sheet without the use of AutoCAD. I have written a program that, with a little data about beam or column, will create the detail sheet automatically. Output of this program is a DXF file and it can be shown in AutoCAD or it can be plotted with it. This program can save the time for drawing the detail sheet with AutoCAD. If you are an AutoCAD operator, you will understand the meaning of words that are used in this article, or if you are a programmer who wants to write a program to create DXF files, first you need a little knowledge about AutoCAD or the drawing programs such as is mentioned above. This code can be useful for programmers who need to create DXF files from their programs. CadLib is not the best one and also there are many commercial software for creating DXF files but they are not open source. Feel free to change the code. Your comments in regards to this article will cause the improvement of CadLib.
Arc, Point and InsertBlock
commands for ENTITIES section
CDrawing class to store drawing data in memory and change
the data before saving it as a DXF file. CDrawing class
CDrawing class when writing data to a DXF
file PolyLine command (by Tran duy Dung)
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Last Updated: 25 Aug 2004 Editor: Nishant Sivakumar |
Copyright 2002 by Omid Shahabi Everything else Copyright © CodeProject, 1999-2010 Web11 | Advertise on the Code Project |
