How To Draw A Line In Java Graphics

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Last Updated on ten August 2019   | Print Email

In this Coffee graphics tutorial, you volition learn how to describe lines with various code examples.

A line is a graphics primitive that connects 2 points. In Java, to depict a line between two points (x1, y1) and (x2, y2) onto graphics context represented by a Graphicsobject, employ the following method:

drawLine(int x1, int y1, int x2, int y2)

If a Graphics2D object is used, the following method is more than object-oriented:

draw(Line2D)

With two implementations of Line2D: Line2D.Double (with double coordinates) and Line2D.Float (with bladder coordinates).

Both methods draw a line using the electric current graphic attributes (paint color, stroke, rendering hints, etc). Here is a quick case (suppose that g2d is a reference of a Graphics2D object):

// draw a line in integer coordinates g2d.drawLine(20, l, 460, 50);  // draw a line in double coordinates g2d.draw(new Line2D.Double(21.5d, 199.8d, 459.5d, 199.8d));  // draw a line in float coordinates g2d.depict(new Line2D.Float(21.50f, 232.50f, 459.50f, 232.50f));

The following source code is a Swing program that draws three lines onto the graphics context of the JFrame window:

package net.codejava.graphics;  import java.awt.Graphics; import coffee.awt.Graphics2D; import java.awt.geom.Line2D;  import javax.swing.JFrame; import javax.swing.SwingUtilities;  /**  * This plan demonstrates how to draw lines using Graphics2D object.  * @author www.codejava.net  *  */ public course LinesDrawingExample extends JFrame {  	public LinesDrawingExample() { 		super("Lines Cartoon Demo");  		setSize(480, 200); 		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 		setLocationRelativeTo(cypher); 	}  	void drawLines(Graphics g) { 		Graphics2D g2d = (Graphics2D) one thousand;  		g2d.drawLine(120, 50, 360, 50);  		g2d.draw(new Line2D.Double(59.second, 99.8d, 419.1d, 99.8d));  		g2d.draw(new Line2D.Float(21.50f, 132.50f, 459.50f, 132.50f));  	}  	public void paint(Graphics chiliad) { 		super.paint(g); 		drawLines(m); 	}  	public static void main(Cord[] args) { 		SwingUtilities.invokeLater(new Runnable() { 			@Override 			public void run() { 				new LinesDrawingExample().setVisible(true); 			} 		}); 	} }

Here, the cardinal point is to override the paint() method from the superclass (JFrame) and then that we can obtain the graphics context:

public void paint(Graphics one thousand) { 	super.paint(g); 	drawLines(grand); }

And hither is the screenshot of the plan:

At present, let's see more than complex examples in which we will alter the graphics attributes in order to decorate the lines drawn. Annotation that the graphics attributes must be gear up before drawing the lines.

Setting pigment color and thickness for the lines

To specify a specific color for the line, telephone call setColor(Color) method before drawing, for case:

g2d.setColor(Color.Red);

To specify thickness for the line, nosotros can create a basic stroke with a specified width equally follows:

// creates a solid stroke with line width is ii Stroke stroke = new BasicStroke(2f);

Then set this stroke for the graphics context:

g2d.setStroke(stroke);

The previous case is updated as follows:

g2d.setColor(Color.RED); // creates a solid stroke with line width is two Stroke stroke = new BasicStroke(2f); g2d.setStroke(stroke); g2d.drawLine(120, 50, 360, 50);  g2d.setColor(Color.Greenish); g2d.setStroke(new BasicStroke(4f)); g2d.draw(new Line2D.Double(59.second, 99.8d, 419.1d, 99.8d));  g2d.setColor(Colour.BLUE); g2d.setStroke(new BasicStroke(6f)); g2d.draw(new Line2D.Float(21.50f, 132.50f, 459.50f, 132.50f));

Event:

Cartoon dashed lines:

To depict a dashed line, specify a dashing pattern when creating the stroke. For example:

bladder[] dashingPattern1 = {2f, 2f}; Stroke stroke1 = new BasicStroke(2f, BasicStroke.CAP_BUTT, 		BasicStroke.JOIN_MITER, 1.0f, dashingPattern1, two.0f);  g2d.setStroke(stroke1); g2d.drawLine(120, 50, 360, 50);

The dashing pattern is formed by alternate between opaque and transparent sections with the widths specified by the float array:

float[] dashingPattern1 = {2f, 2f};

This design specifies that the first two pixels are opaque; the next ii are transparent; the adjacent two are opaque; and so on…. Here's the result:

The original example is updated to depict dashed lines as follows:

g2d.setColor(Color.RED);  float[] dashingPattern1 = {2f, 2f}; Stroke stroke1 = new BasicStroke(2f, BasicStroke.CAP_BUTT, 		BasicStroke.JOIN_MITER, 1.0f, dashingPattern1, 2.0f);  g2d.setStroke(stroke1); g2d.drawLine(120, l, 360, 50);  g2d.setColor(Color.GREEN);  float[] dashingPattern2 = {10f, 4f}; Stroke stroke2 = new BasicStroke(4f, BasicStroke.CAP_BUTT, 		BasicStroke.JOIN_MITER, 1.0f, dashingPattern2, 0.0f);  g2d.setStroke(stroke2); g2d.depict(new Line2D.Double(59.2nd, 99.8d, 419.1d, 99.8d));  g2d.setColor(Color.Blueish);  float[] dashingPattern3 = {10f, 10f, 1f, 10f}; Stroke stroke3 = new BasicStroke(4f, BasicStroke.CAP_SQUARE, 		BasicStroke.JOIN_MITER, i.0f, dashingPattern3, 0.0f);  g2d.setStroke(stroke3); g2d.depict(new Line2D.Float(21.50f, 132.50f, 459.50f, 132.50f));

Hither's the result:

Decorating line end caps

Caps are decorations practical at both ends of a line (solid, unclosed-path line) or dash segments in a dashed line. The BasicStroke grade provides three cap styles: CAP_SQUARE (default), CAP_BUTT and CAP_ROUND. The following instance creates 3 strokes with different cap styles:

// this stroke with default CAP_SQUARE and JOIN_MITER Stroke stroke1 = new BasicStroke(12f);  // this stroke with CAP_BUTT Stroke stroke2 = new BasicStroke(12f, BasicStroke.CAP_BUTT, BasicStroke.JOIN_MITER);  // this stroke with CAP_ROUND Stroke stroke3 = new BasicStroke(12f, BasicStroke.CAP_ROUND, BasicStroke.JOIN_MITER);

And the following code snippet draws three lines with these strokes:

g2d.setStroke(stroke1); g2d.drawLine(xxx, 60, 450, 60);  g2d.setStroke(stroke2); g2d.drawLine(30, 100, 450, 100);  g2d.setStroke(stroke3); g2d.drawLine(xxx, 140, 450, 140);

Here'south the result:

Decorating line joins

Joins are decorations applied at intersections between lines. The BasicStroke class provides three join styles: JOIN_MITER (default), JOIN_BEVEL and JOIN_ROUND. The following example creates three strokes with dissimilar join styles:

// this stroke with default CAP_SQUARE and JOIN_MITER Stroke stroke1 = new BasicStroke(12f);  // this stroke with JOIN_BEVEL Stroke stroke2 = new BasicStroke(12f, BasicStroke.CAP_SQUARE, BasicStroke.JOIN_BEVEL);  // this stroke with JOIN_ROUND Stroke stroke3 = new BasicStroke(12f, BasicStroke.CAP_SQUARE, BasicStroke.JOIN_ROUND);

And the following code snippet draws three rectangles using lines to demonstrate the concept of bring together decorations:

// draws the first rectangle with a stroke of JOIN_MITER g2d.setStroke(stroke1); g2d.drawLine(30, 60, 120, 60); g2d.drawLine(30, 60, 30, 150); g2d.drawLine(120, 60, 120, 150); g2d.drawLine(120, 60, 120, 150); g2d.drawLine(xxx, 150, 120, 150);  // draws the second rectangle with a stroke of JOIN_BEVEL g2d.setStroke(stroke2); g2d.drawLine(30 + 120, threescore, 120 + 120, lx); g2d.drawLine(30 + 120, 60, 30 + 120, 150); g2d.drawLine(120 + 120, 60, 120 + 120, 150); g2d.drawLine(120 + 120, sixty, 120 + 120, 150); g2d.drawLine(30 + 120, 150, 120 + 120, 150);  // draws the third rectangle with a stroke of JOIN_ROUND g2d.setStroke(stroke3); g2d.drawLine(xxx + 240, 60, 120 + 240, 60); g2d.drawLine(30 + 240, 60, 30 + 240, 150); g2d.drawLine(120 + 240, 60, 120 + 240, 150); g2d.drawLine(120 + 240, 60, 120 + 240, 150); g2d.drawLine(xxx + 240, 150, 120 + 240, 150);

Hither's the result:

API References:

• Graphics2D Javadoc
• BasicStroke Javadoc
• Line2D.Double Javadoc
• Line2D.Bladder Javadoc

Other Java Graphics Tutorials:

• How to add watermark for images using Coffee
• How to resize images using Coffee
• How to catechumen paradigm format using Java
• How to draw epitome with automatic scaling in Java
• How to capture screenshot programmatically in Java
• How to draw text vertically with Java Graphics2D
• How to Create Zoomable User Interface Java Programs with Piccolo2D Framework
• Drawing Rectangles Examples with Coffee Graphics2D
• Using JFreechart to describe line chart with CategoryDataset
• Using JFreechart to draw XY line nautical chart with XYDataset

About the Writer:

Nam Ha Minh is certified Coffee programmer (SCJP and SCWCD). He started programming with Java in the time of Java i.4 and has been falling in dear with Java since then. Make friend with him on Facebook and lookout his Java videos yous YouTube.

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Source: https://www.codejava.net/java-se/graphics/drawing-lines-examples-with-graphics2d

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