绘制、保存图形

绘制、保存图形

耿祥义

我们绘制一个圆和一个太极图，并将绘制的图形保存成图像。保存的太极图和圆的图像如下图所示意。

一、涉及的主要知识点见教材第14章

BufferedImage类的对象称作一个缓存图像。缓存图像自带一个 Graphics对象，该对象可以向缓存图像上绘制图形。

2.java.awt.Graphics类

Graphics类提供了各种绘制图形的方法。

3.java.awt.Graphics2D类

Graphics2D类提供的draw(Shape shape)和fill(Shape shape)方法可以绘制或填充实现Shape接口的类的实例，即可以绘制各种图形对象，例如，Ellipse2D椭圆图形对象。

4.javax.imageio.ImageIO

ImageIO类的静态方法：

public static boolean write

(RenderedImage im,

String formatName,

File output)

将图像im写入到文件output。formatName参数指定图像的编码格式，例如："jpeg","bmp"等。

im必须是实现RenderedImage接口的类的实例(BufferedImage类实现了RenderedImage接口）。

二、视频讲解

将

https://share.weiyun.com/3Qe3AN5W

复制到浏览器地址栏访问即可。

接口：Drawer.java

public interface Drawer {

BufferedImage getImage();

}

实现接口的类：DrawCircle.java负责绘制圆到缓存图像

import java.awt.Graphics2D;

import java.awt.Graphics;

import java.awt.Color;

//负责绘制圆：

public class DrawCircle implements Drawer {

public BufferedImage getImage(){

int width=320, height=300;

int r = 110;

BufferedImage image =

new BufferedImage

(width,height,BufferedImage.TYPE_INT_RGB);

Graphics g = image.getGraphics();

//g默认用白色绘制图形

g.fillRect(0, 0, width, height);

Graphics2D g_2d=(Graphics2D)g;

Ellipse2D ellipse=

new Ellipse2D.Double(160-r,150-r,2*r,2*r);

g_2d.setColor(Color.blue);

g_2d.draw(ellipse);

return image;

}

}

实现接口的类：DrawTaiJi.java负责绘制太极图到缓存图像

import java.awt.Graphics2D;

import java.awt.Graphics;

import java.awt.Color;

//负责绘制太极图：

public class DrawTaiJi implements Drawer {

public BufferedImage getImage(){

int width=300, height=300;

int r = width/8;

BufferedImage image =

new BufferedImage

(width,height,BufferedImage.TYPE_INT_RGB);

Graphics g = image.getGraphics();

g.setColor(Color.gray);

//设置图像是灰色底色（默认是黑色）：

g.fillRect(0, 0, width, height);

Graphics2D g_2d=(Graphics2D)g;

Arc2D arc=

new Arc2D.Double

(0,0,width,height,-90,-180,Arc2D.PIE);

g_2d.setColor(Color.black);

g_2d.fill(arc);

g_2d.setColor(Color.white);

arc.setArc

(0,0,width,height,-90,180,Arc2D.PIE);

g_2d.fill(arc);

arc.setArc

(width/4,0,width/2,height/2,-90,-180,Arc2D.PIE);

g_2d.fill(arc);

g_2d.setColor(Color.black);

Ellipse2D ellipse=

new Ellipse2D.Double

(width/2-r/2,height/4-r/2,r,r);

g_2d.fill(ellipse);

arc.setArc

(width/4,height/2,width/2,height/2,90,-180,Arc2D.PIE);

g_2d.fill(arc);

g_2d.setColor(Color.white);

ellipse.setFrame

(width/2-r/2,3*height/4-r/2,r,r);

g_2d.fill(ellipse);

return image;

}

}

负责将图形保存为图像的类：MakeImage.java

import javax.imageio.ImageIO;

import java.io.File;

public class MakeImage {

public static void drawAndSaveGeometry

(Drawer drawer, String formatName,File imageFile) {

try {

boolean boo =

ImageIO.write

(drawer.getImage(),formatName,imageFile);

}

catch(Exception exp){}

}

}

主类：MainClass.java

import java.io.File;

public class MainClass {

public static void main(String args[]){

Drawer drawer = new DrawCircle();

File f = new File("circle.jpg");

//保存一个圆图像circle.jpg

MakeImage.drawAndSaveGeometry

(drawer,"jpeg",f);

drawer = new DrawTaiJi();

f = new File("taiji.bmp");

//保存一个太极图像taiji.bmp

MakeImage.drawAndSaveGeometry

(drawer,"bmp",f);

}

}