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用CabLib創建DXF(繪圖交換格式)文件

編輯：關於VC++

介紹

什麼是DXF

繪圖交換格式(DXF)文件允許在AutoCAD和其它程序進行圖形交換。DXF文件即可以是ASCII格式也可以是二進制格式。因為ASCII格式的DXF文件比二進制格式更加通用，所以CadLib使用ASCII的DXF格式。

什麼是CadLib

CadLib不是計算機輔助設計(CAD)程序。它是創建用於CAD程序DXF文件的工具。它由兩部分組成，一部分是用於創建DXF文件的動態鏈接庫，另一部分是編程接口，該類封裝了cadio.dll中的函數，可以在Microsoft Visual C++項目中使用。另外，cadio.dll 也可以用於其它Win32編程中。

為什麼使用CadLib

一些程序需要輸出可以被AutoCad等程序使用的圖形文件，例如，在一個"發動機設計程序"中，程序需要輸出圖形，而最常用的交換數據的圖形格式便是DXF。

DXF文件結構

DXF文件格式是圖形文件中所有信息的標簽數據描述。標簽數據指的是文件中的被稱為群碼的整型數據前的每個數據項。群碼的值指示了下面數據的數據類型以及數據單元的含義。事實上圖形文件中所有用戶特殊信息都可以描述為DXF格式。（參考AutoCad的DXF參考說明)

DXF文件由許多區域組成，每個區域裡有許多圖形數據，CadLib可以使用如下區域：

1. 頭部 HEADER

2. 表格 TABLES

3. 區塊 BLOCKS

4. 實體 ENTITIES

CadLib中的DXF文件結構參考AutoCad中的DXF格式說明，具體可以在下面網址找到參考：

http://www.autodesk.com/techpubs/autocad/acad2000/dxf/dxf_format.htm

http://www.martinreddy.net/gfx/3d/DXF12.spec

類

這裡的類是CadIO.dll和主程序之間的接口。"Test"演示了如何用CadLib中的CDxfFileWrite和CDrawing類創建DXF文件。

CDxfFileWrite類

CDxfFileWrite封裝了直接創建DXF文件的所有命令。使用方法如下：

1. 創建DXF文件

CDxfFileWrite dxffile; dxffile.Create( "d:\\test.dxf" );

2. HEADER區域的開始與結束。這裡是為了兼容CAD程序。其它的不需要HEADER區域。

// Header Section ------------------------------------------ dxffile.BeginSection(SEC_HEADER); dxffile.EndSection(); // close HEADER section ------------------------------------

3. 開始表格區域並放置LAYER, LTYPE, STYLE, DIMSTYLE等你所需的表格類型，然後結束該區域。

// 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 ------------------------------------

4. 開始實體區域並放置LINE, CIRCLE, SOLID, TEXT, ARC, POINT, DIMLINEAR等數據，然後結束該區域。

// 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 ----------------------------------

5. 關閉DXF文件

dxffile.Close();

CDrawing 類

CDrawing封裝了在內存中創建圖形並保存到DXF文件中的功能。使用方法如下：

1. 創建內存繪圖

CDrawing drw; drw.Create();

2. 在內存中創建LAYER, LTYPE, STYLE, DIMSTYLE等所需要的表格類型

// 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);

3. 生成實體數據(LINE, CIRCLE, SOLID, TEXT, ARC, POINT, DIMLINEAR, POLYLINE)

// 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");