第5章Java图形处理解说.ppt

【例5.3】演示了几何形状、笔画变换以及颜色渐变显示。其中直线的笔画宽度为10，其它笔画宽度为5，中间三个图形实现绿色到蓝色的循环渐变，后三个图形实现红色到黄色的循环渐变，如图5.4所示。 //程序文件名GUI2D.java import java.awt.*; import java.applet.*; import java.awt.geom.*; public class GUI2D extends Applet { public void paint(Graphics oldg) { Graphics2D g = (Graphics2D)oldg; //设置笔画宽度 BasicStroke stroke = new BasicStroke(10); g.setStroke(stroke); //画线 Line2D line = new Line2D.Float(0,0,20,30); g.draw(line); line = new Line2D.Float(50,50,100,50); g.draw(line); line = new Line2D.Float(50,50,50,100); g.draw(line); stroke = new BasicStroke(5); g.setStroke(stroke); //设置渐变填充 GradientPaint gt = new GradientPaint(0,0,Color.green,50,30,Color.blue,true); g.setPaint((Paint)gt); //画矩形 Rectangle2D rect = new Rectangle2D.Float(80,80,40,40); g.draw(rect); rect = new Rectangle2D.Float(100,100,40,40); g.fill(rect); //画椭圆 Ellipse2D ellipse = new Ellipse2D.Float(120,120,30,40); g.draw(ellipse); gt = new GradientPaint(0,0,Color.red,30,30,Color.yellow,true); g.setPaint((Paint)gt); ellipse = new Ellipse2D.Float(140,140,20,20); g.fill(ellipse); //画圆角矩形 RoundRectangle2D roundRect = new RoundRectangle2D.Float(160,160,40,40,20,20); g.draw(roundRect); roundRect = new RoundRectangle2D.Float(180,180,40,40,20,20); g.fill(roundRect); //画几何图形 GeneralPath path = new GeneralPath(); path.moveTo(150,0); path.lineTo(160,50); path.curveTo(190,200,240,140,200,100); g.fill(path); } } 图5.4 通过Graphics2D对象绘制形状 5.5.2 绘制文本 Graphics2D类提供一个文本布局(TextLayout)对象，用于实现各种字体或段落文本的绘制。其构造函数为： public TextLayout(String string, Font font, FontRenderContext frc) 通过字符串string和字体font构造布局。 public void draw(Graphics2D g2, float x, float y) 将这个TextLayout对象画到Graphics2D对象g2上的x，y坐标处。 public Rectangle2D getBounds() 返回TextLayout对象的区域。 【例5.4】测试绘制文本功能，如图5.5所示。源程序代码如下： //程序文件GUIText.java import java.awt.*; import java.applet.*; import java.awt.geom.*; import java.awt.font.*; public class GUIText extends Ap