java 生成图片（仪表盘）

package ict.dashboard;

import java.awt.*;
import java.awt.image.*;
import java.io.*;
import javax.imageio.*;
import java.awt.font.FontRenderContext;
import java.awt.geom.Rectangle2D;

public class Dashboard{

    public static void generateImage(OutputStream os, double percent, int radius){

        //
        try{
            BufferedImage canvas = new BufferedImage(radius + radius, radius + radius, BufferedImage.TYPE_4BYTE_ABGR);
            Graphics2D g = (Graphics2D)canvas.createGraphics();//Graphics2D用于画图
            BufferedImage bg = ImageIO.read(new File("./image/bg.png"));//仪表盘背景
            BufferedImage pointer = ImageIO.read(new File("./image/pointer.png"));//仪表盘指针

            int pw = pointer.getWidth();
            int ph = pointer.getHeight();

            g.drawImage(bg, 0, 0, radius + radius, radius + radius, null);

            if(percent > 1.0) percent = 1.0;
            else if(percent < 0.0) percent = 0.0;
            double arc = Math.PI / 6.0 + percent * 300 / 360 * Math.PI * 2;

            g.rotate(arc, radius, radius);//旋转
            g.drawImage(pointer, radius - pw / 2, radius - 40, 20, radius, null);

            g.rotate(-arc, radius, radius);
            String ps = String.valueOf(percent);
            if(ps.length() > 5) ps = ps.substring(0, 5);//截断字符串
            FontRenderContext context = g.getFontRenderContext();
            Font font = new Font("Serif", Font.BOLD, 20);
            Rectangle2D bounds = font.getStringBounds(ps, context);//获取字符串边界信息，如长、宽等
            g.setColor(Color.WHITE);
            g.fillRect((int)(radius - bounds.getWidth() / 2) - 1, (int)(radius - bounds.getHeight() / 2) - 1, (int)bounds.getWidth() + 1, (int)bounds.getHeight() + 1);
            g.setColor(Color.BLACK);
            g.setFont(font);//字体设置
            g.drawString(ps, (int)(radius - bounds.getWidth() / 2), (int)(radius - bounds.getHeight() / 2 - bounds.getY()));//显示比率

            ImageIO.write(canvas, "png", os);//生成图片到outputstream
        }
        catch(Exception ex){

            System.out.println("generate image error!");
            System.out.println(ex);
        }
    }

    public static void main(String[] args) throws Exception{

//-10.0到370度的测试
        for(double i = -10.0; i < 370.1; i += 10.0){

            FileOutputStream fos = new FileOutputStream(new File("./" + i + ".png"));
            generateImage(fos, i / 360.0, 200);
            fos.close();
        }
    }
}