如何使用jdxf库在Java中设置DXF图层颜色，让实体继承该颜色？

问题现状 #

使用jdxf库生成DXF文件时，无法实现**图层设置指定颜色，实体颜色继承图层（ByLayer）**的需求：当前代码仅能直接给实体设置颜色，但图层默认颜色为黑白，生成的DXF中实体是单独的颜色，未关联图层颜色。

原有代码 #

DXFHandler类 #

public class DXFHandler {
    DXFGraphics graphics;
    DXFDocument dXFDocument;
    int mirrorY, mirrorX;

    public DXFHandler() {
        dXFDocument = new DXFDocument();
        dXFDocument.setUnits(4);//set units to mm
        dXFDocument.setPrecisionDigits(1);//set precision digits
        dXFDocument.setViewportCenter(0, 0);        
        graphics = dXFDocument.getGraphics();
        mirrorX=1;
        mirrorY=-1;
    }

    public void addLayer(String layerName, Color c) {
        dXFDocument.setLayer(layerName);      
        graphics.setColor(c);//This will only achieve that the drawing entities get this color, but the layer's color would not be touched.      
    }
    public void drawLine(double[]x, double[]y){
         if (x!=null&&y!=null&x.length==y.length) {
            for (int i = 1; i < x.length; i++) {
                graphics.drawLine(mirrorX*x[i-1], mirrorY*y[i-1],mirrorX*x[i],mirrorY*y[i]);
            }
        }
    }
    public void drawPoint(double[]x, double[]y){
        if (x!=null&&y!=null&x.length==y.length) {
            for (int i = 0; i < x.length; i++) {
                graphics.drawPoint(mirrorX*x[i], mirrorY*y[i]);
            }
        }
    }
    public void drawRect(double x1, double y1, double x2, double y2){
        graphics.drawRect(mirrorX*x1, mirrorY*y1, mirrorX*x2, mirrorY*y2);
    }

    public void saveToDXF(String outputPath) throws IOException {
        String stringOutput = dXFDocument.toDXFString();
        FileWriter fileWriter = new FileWriter(outputPath);
        fileWriter.write(stringOutput);
        fileWriter.flush();
        fileWriter.close();
    }
}

测试代码 #

public static void main(String[] args) {
    String outputFile="d:\\test.dxf";
    int points=500;//Number of drawn points .
    String layer1Name="Layer_1";
    double[]xCoordinatesOfPoints1=new double[points];//creating first test-pointset_Xcoordinates
    double[]yCoordinatesOfPoints1=new double[points];//creating first test-pointset_Ycoordinates
    for (int i = 0; i < xCoordinatesOfPoints1.length; i++) {
        xCoordinatesOfPoints1[i]=i;
        yCoordinatesOfPoints1[i]=i;
    }                
    String layer2Name="Layer_2";
    double[]xCoordinatesOfPoints2=new double[points];//creating second test-pointset_Xcoordinates
    double[]yCoordinatesOfPoints2=new double[points];//creating second test-pointset_Ycoordinates
    for (int i = 0; i < xCoordinatesOfPoints1.length; i++) {
        xCoordinatesOfPoints2[i]=-1*i;
        yCoordinatesOfPoints2[i]=i;
    }
     
    DXFHandler dXFHandler=new DXFHandler(); //Creating dxf handler object        
    dXFHandler.addLayer(layer1Name, Color.red);//Creating layer1
    dXFHandler.drawPoint(xCoordinatesOfPoints1, yCoordinatesOfPoints1);//drawing points of layer1
    dXFHandler.addLayer(layer2Name, Color.GREEN);//Creating layer2
    dXFHandler.drawPoint(xCoordinatesOfPoints2, yCoordinatesOfPoints2);//drawing points of layer2
    try {
        dXFHandler.saveToDXF(outputFile);//Exporting dxf file
    } catch (IOException ex) {
        System.out.println("FAILED");
    }
}

解决方案 #

修改addLayer方法，直接操作DXFLayer对象设置图层颜色，同时将绘图上下文的颜色设为0（代表ByLayer），让实体继承图层颜色：

修改后的DXFHandler关键代码 #

public void addLayer(String layerName, Color c) {
    // 获取或创建目标图层
    DXFLayer layer = dXFDocument.getLayer(layerName);
    // 将Java Color转换为DXF颜色索引
    int dxfColor = DXFColor.getClosestDXFColorIndex(c);
    // 设置图层颜色
    layer.setColor(dxfColor);
    // 切换到该图层
    dXFDocument.setLayer(layerName);
    // 设置图形上下文颜色为ByLayer（DXF颜色代码0）
    graphics.setColor(0);
}

完整修改后的DXFHandler类 #

public class DXFHandler {
    DXFGraphics graphics;
    DXFDocument dXFDocument;
    int mirrorY, mirrorX;

    public DXFHandler() {
        dXFDocument = new DXFDocument();
        dXFDocument.setUnits(4);//set units to mm
        dXFDocument.setPrecisionDigits(1);//set precision digits
        dXFDocument.setViewportCenter(0, 0);        
        graphics = dXFDocument.getGraphics();
        mirrorX=1;
        mirrorY=-1;
    }

    public void addLayer(String layerName, Color c) {
        DXFLayer layer = dXFDocument.getLayer(layerName);
        int dxfColor = DXFColor.getClosestDXFColorIndex(c);
        layer.setColor(dxfColor);
        dXFDocument.setLayer(layerName);
        graphics.setColor(0); // 设置为ByLayer模式
    }
    public void drawLine(double[]x, double[]y){
         if (x!=null&&y!=null&x.length==y.length) {
            for (int i = 1; i < x.length; i++) {
                graphics.drawLine(mirrorX*x[i-1], mirrorY*y[i-1],mirrorX*x[i],mirrorY*y[i]);
            }
        }
    }
    public void drawPoint(double[]x, double[]y){
        if (x!=null&&y!=null&x.length==y.length) {
            for (int i = 0; i < x.length; i++) {
                graphics.drawPoint(mirrorX*x[i], mirrorY*y[i]);
            }
        }
    }
    public void drawRect(double x1, double y1, double x2, double y2){
        graphics.drawRect(mirrorX*x1, mirrorY*y1, mirrorX*x2, mirrorY*y2);
    }

    public void saveToDXF(String outputPath) throws IOException {
        String stringOutput = dXFDocument.toDXFString();
        FileWriter fileWriter = new FileWriter(outputPath);
        fileWriter.write(stringOutput);
        fileWriter.flush();
        fileWriter.close();
    }
}

原理说明 #

1. dXFDocument.getLayer(layerName)：如果图层不存在会自动创建，返回对应的DXFLayer对象
2. DXFColor.getClosestDXFColorIndex(c)：将Java的Color对象转换为DXF标准的颜色索引值
3. layer.setColor(dxfColor)：直接设置图层本身的颜色
4. graphics.setColor(0)：DXF中颜色代码0代表ByLayer，后续绘制的所有实体都会自动继承当前图层的颜色

运行修改后的代码，生成的DXF文件中：

• 图层Layer_1颜色为红色，Layer_2颜色为绿色
• 所有实体的颜色模式为"ByLayer"，会跟随图层颜色变化

内容的提问来源于stack exchange，提问作者mnystrktr