android 生成验证码图片

（转自：http://blog.csdn.net/onlyonecoder/article/details/8231373）

 package com.nobeg.util;

 import java.util.Random;

 import android.graphics.Bitmap;
 import android.graphics.Canvas;
 import android.graphics.Color;
 import android.graphics.Paint;
 import android.graphics.Bitmap.Config;

 public class Code {

     private static final char[] CHARS = {
         '2', '3', '4', '5', '6', '7', '8', '9',
         'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'j', 'k', 'l', 'm',
         'n', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
         'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
         'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'
     };

     private static Code bmpCode;

     public static Code getInstance() {
         if(bmpCode == null)
             bmpCode = new Code();
         return bmpCode;
     }

     //default settings
     private static final int DEFAULT_CODE_LENGTH = 3;
     private static final int DEFAULT_FONT_SIZE = 40;
     private static final int DEFAULT_LINE_NUMBER = 2;
     private static final int BASE_PADDING_LEFT = 20, RANGE_PADDING_LEFT = 15, BASE_PADDING_TOP = 30, RANGE_PADDING_TOP = 20;
     private static final int DEFAULT_WIDTH = 130, DEFAULT_HEIGHT = 80;

     //settings decided by the layout xml
     //canvas width and height
     private int width = DEFAULT_WIDTH, height = DEFAULT_HEIGHT; 

     //random word space and pading_top
     private int base_padding_left = BASE_PADDING_LEFT, range_padding_left = RANGE_PADDING_LEFT,
             base_padding_top = BASE_PADDING_TOP, range_padding_top = RANGE_PADDING_TOP;

     //number of chars, lines; font size
     private int codeLength = DEFAULT_CODE_LENGTH, line_number = DEFAULT_LINE_NUMBER, font_size = DEFAULT_FONT_SIZE;

     //variables
     private String code;
     private int padding_left, padding_top;
     private Random random = new Random();
     //验证码图片
     public Bitmap createBitmap() {
         padding_left = 0;

         Bitmap bp = Bitmap.createBitmap(width, height, Config.ARGB_8888);
         Canvas c = new Canvas(bp);

         code = createCode();

         c.drawColor(Color.WHITE);
         Paint paint = new Paint();
         paint.setTextSize(font_size);

         for (int i = 0; i < code.length(); i++) {
             randomTextStyle(paint);
             randomPadding();
             c.drawText(code.charAt(i) + "", padding_left, padding_top, paint);
         }

         for (int i = 0; i < line_number; i++) {
             drawLine(c, paint);
         }

         c.save( Canvas.ALL_SAVE_FLAG );//保存
         c.restore();//
         return bp;
     }

     public String getCode() {
         return code;
     }

     //验证码
     private String createCode() {
         StringBuilder buffer = new StringBuilder();
         for (int i = 0; i < codeLength; i++) {
             buffer.append(CHARS[random.nextInt(CHARS.length)]);
         }
         return buffer.toString();
     }

     private void drawLine(Canvas canvas, Paint paint) {
         int color = randomColor();
         int startX = random.nextInt(width);
         int startY = random.nextInt(height);
         int stopX = random.nextInt(width);
         int stopY = random.nextInt(height);
         paint.setStrokeWidth(1);
         paint.setColor(color);
         canvas.drawLine(startX, startY, stopX, stopY, paint);
     }

     private int randomColor() {
         return randomColor(1);
     }

     private int randomColor(int rate) {
         int red = random.nextInt(256) / rate;
         int green = random.nextInt(256) / rate;
         int blue = random.nextInt(256) / rate;
         return Color.rgb(red, green, blue);
     }

     private void randomTextStyle(Paint paint) {
         int color = randomColor();
         paint.setColor(color);
         paint.setFakeBoldText(random.nextBoolean());  //true为粗体，false为非粗体
         float skewX = random.nextInt(11) / 10;
         skewX = random.nextBoolean() ? skewX : -skewX;
         paint.setTextSkewX(skewX); //float类型参数，负数表示右斜，整数左斜
 //        paint.setUnderlineText(true); //true为下划线，false为非下划线
 //        paint.setStrikeThruText(true); //true为删除线，false为非删除线
     }

     private void randomPadding() {
         padding_left += base_padding_left + random.nextInt(range_padding_left);
         padding_top = base_padding_top + random.nextInt(range_padding_top);
     }
 }

调用：

    /**
     * 生成验证码
     */
    private void createConfirmCode(){
        mImageView.setImageBitmap(ConfirmCode.getInstance()
                .createBitmap());
        String Code = ConfirmCode.getInstance().getCode();

    }