最近遇到了一個驗(yàn)證碼識別的問題，不過經(jīng)過觀察該驗(yàn)證碼相當(dāng)?shù)暮喡?，且看下面幾個驗(yàn)證碼圖片的例子：
事實(shí)上，上面我已經(jīng)把所有可能的字符都列出來了，包含0~9A-Z共36個字符。這16張圖片都有下面幾個共同特征：
- 背景色都是白色或者是純色
- 前景色都不是白色
- 文字都很規(guī)則，沒有做過扭曲處理
- 圖片大小都是40x10個像素
- 每張圖片上都只有4個字符
- 結(jié)合特征4和特征5來看，每個字符都是占據(jù)了10x10個像素
- 沒有噪音
就上面這些特征決定了，我們要識別這些驗(yàn)證非常的簡單，識別率絕對是100%。這種驗(yàn)證碼就是純同虛設(shè)。
下面我們就用簡單的代碼來識別它。
首先采集36個字符的圖像特征到一個數(shù)據(jù)庫（廣義的，我們這里就用一個簡單的Map來存儲）：
首先我們把上面包含了所有36個字符的16個圖片存放在同一個目錄下，并將其文件名定為字符上的文字，比如第一張圖片就叫“0JQT.bmp”。
接
著我們寫一個小程序來將所有字符的編碼采集下來并保存成一個映射文件，采集特征信息的大體過程是先把一張40x10的圖片分割成4張10x10的圖片（因
為一個10x10上就是一個字符），然后分別掃描每個10x10的圖片，記錄每個像素的特征，假如這個像素是白色（背景是白色，經(jīng)過代碼計算發(fā)現(xiàn)這個背景
并不是那么的白，而是255,250,250，所以你看到代碼中判斷是否是白色用的是 >= 250 而不是
255）那么記錄為1，否則記錄為0，然后把10x10=100個像素的0、1標(biāo)識拼接成一個字符串，這個字符串就代表一個字符了。
/**
* Created on 2007-11-18 下午03:33:28
*/
import java.awt.Image;
import java.awt.image.PixelGrabber;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FilenameFilter;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;
import javax.imageio.ImageIO;
import org.apache.commons.io.FilenameUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
* @author sutra
*
*/
public class Gather {
private static final Log log = LogFactory.getLog(Gather.class);
private static int handleSinglePixel(int x, int y, int pixel) {
// int alpha = (pixel >> 24) & 0xff;
int red = (pixel >> 16) & 0xff;
int green = (pixel >> 8) & 0xff;
int blue = (pixel) & 0xff;
// Deal with the pixel as necessary...
log.debug(x + "," + y + ":" + red + "," + green + "," + blue);
int white = 0;
if (red >= 250 && green >= 250 && blue >= 250) {
white = 1;
}
// System.out.println(String.format("%1$s,%2$s:%3$s", x, y, w));
return white;
}
public static String[] gather(Image src) throws InterruptedException {
int width = src.getWidth(null); // 得到源圖寬
int height = src.getHeight(null); // 得到源圖長
log.debug("width: " + width);
log.debug("height: " + height);
int pixels[] = new int[width * height];
PixelGrabber pg = new PixelGrabber(src, 0, 0, width, height, pixels, 0,
width);
pg.grabPixels();
String[] ret = new String[4];
for (int x = 0; x < 40; x += 10) {
int y = 0;
StringBuilder sb = new StringBuilder();
for (int j = 0; j < height; j++) {
for (int i = x; i < x + 10; i++) {
int w = handleSinglePixel(x + i, y + j, pixels[j * width
+ i]);
sb.append(w);
}
}
log.debug(x + ":" + sb.toString());
ret[x / 10] = sb.toString();
}
return ret;
}
/**
* @param args
* @throws Exception
*/
public static void main(String[] args) throws Exception {
File bmpDir = new File("src/main/bmp/");
File[] bmps = bmpDir.listFiles(new FilenameFilter() {
public boolean accept(File dir, String name) {
return "bmp".equalsIgnoreCase(FilenameUtils.getExtension(name));
}
});
Map codes = new HashMap();
for (File bmp : bmps) {
log.debug("bmp: " + bmp);
Image src = ImageIO.read(bmp); // 構(gòu)造Image對象
String filename = bmp.getName();
String[] charCodes = gather(src);
for (int i = 0; i < 4; i++) {
char ch = filename.charAt(i);
String code = charCodes[i];
String old;
if ((old = codes.get(ch)) != null) {
if (!old.equals(code)) {
throw new Exception("如果發(fā)生這樣的異常，說明我們的假設(shè)有問題。");
} else {
log.debug("old equals new");
}
} else {
codes.put(ch, code);
}
}
}
char[] allChars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ".toCharArray();
Properties codesDb = new Properties();
for (char ch : allChars) {
log.debug("ch: " + ch);
String code = codes.get(ch);
if (code == null) {
// 做點(diǎn)檢查，如果缺少的話，你需要去收集更多的圖片
throw new Exception("缺少 " + ch);
}
codesDb.put(new String(new char[] { ch }), codes.get(ch));
}
codesDb.list(System.out);
codesDb.store(new FileOutputStream("codes.db"), "codes");
}
}
這樣我們就得到這樣一個映射表：
0:1110000111110111101111011110111101001011110100101111010010111101001011110111101111011110111110000111
1:1111011111110001111111110111111111011111111101111111110111111111011111111101111111110111111100000111
2:1110000111110111101111011110111111111011111111011111111011111111011111111011111111011110111100000011
3:1110000111110111101111011110111111110111111100111111111101111111111011110111101111011110111110000111
4:1111101111111110111111110011111110101111110110111111011011111100000011111110111111111011111111000011
5:1100000011110111111111011111111101000111110011101111111110111111111011110111101111011110111110000111
6:1111000111111011101111011111111101111111110100011111001110111101111011110111101111011110111110000111
7:1100000011110111011111011101111111101111111110111111110111111111011111111101111111110111111111011111
8:1110000111110111101111011110111101111011111000011111101101111101111011110111101111011110111110000111
9:1110001111110111011111011110111101111011110111001111100010111111111011111111101111011101111110001111
A:1111011111111101111111101011111110101111111010111111101011111100000111110111011111011101111000100011
B:1000000111110111101111011110111101110111110000111111011101111101111011110111101111011110111000000111
C:1110000011110111101110111110111011111111101111111110111111111011111111101111101111011101111110001111
D:1000001111110111011111011110111101111011110111101111011110111101111011110111101111011101111000001111
E:1000000111110111101111011011111101101111110000111111011011111101101111110111111111011110111000000111
F:1000000111110111101111011011111101101111110000111111011011111101101111110111111111011111111000111111
G:1110000111110111011110111101111011111111101111111110111111111011100011101111011111011101111110001111
H:1000100011110111011111011101111101110111110000011111011101111101110111110111011111011101111000100011
I:1100000111111101111111110111111111011111111101111111110111111111011111111101111111110111111100000111
J:1110000011111110111111111011111111101111111110111111111011111111101111111110111110111011111000011111
K:1000100011110111011111011011111101011111110001111111010111111101101111110110111111011101111000100011
L:1000111111110111111111011111111101111111110111111111011111111101111111110111111111011110111000000011
M:1000100011110010011111001001111100100111110101011111010101111101010111110101011111010101111001010011
N:1000100011110011011111001101111101010111110101011111010101111101100111110110011111011001111000110111
O:1110001111110111011110111110111011111011101111101110111110111011111011101111101111011101111110001111
P:1000000111110111101111011110111101111011110000011111011111111101111111110111111111011111111000111111
Q:1110001111110111011110111110111011111011101111101110111110111011111011101001101111011001111110001011
R:1000001111110111011111011101111101110111110000111111010111111101101111110110111111011101111000110011
S:1110000011110111101111011110111101111111111001111111111001111111111011110111101111011110111100000111
T:1000000011101101101111110111111111011111111101111111110111111111011111111101111111110111111110001111
U:1000100011110111011111011101111101110111110111011111011101111101110111110111011111011101111110001111
V:1000100011110111011111011101111101110111111010111111101011111110101111111010111111110111111111011111
W:1001010011110101011111010101111101010111110101011111001001111110101111111010111111101011111110101111
X:1000100011110111011111101011111110101111111101111111110111111110101111111010111111011101111000100011
Y:1000100011110111011111011101111110101111111010111111110111111111011111111101111111110111111110001111
Z:1100000011110111011111111101111111101111111110111111110111111111011111111011111111101110111100000011
然后寫一個根據(jù)這個保存好的映射文件來識別圖片的 ImageParser 吧，也很簡單：
/**
* Created on 2007-11-18 下午04:59:12
*/
import java.awt.Image;
import java.io.IOException;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
* @author sutra
*
*/
public class ImageParser {
@SuppressWarnings("unused")
private static final Log log = LogFactory.getLog(ImageParser.class);
private static class SingletonHolder {
public static final ImageParser instance;
static {
try {
instance = new ImageParser();
} catch (IOException e) {
throw new RuntimeException(e);
}
}
}
private Map codes;
/**
* @throws IOException
*
*/
private ImageParser() throws IOException {
codes = new HashMap(36);
Properties p = new Properties();
p.load(ImageParser.class.getResourceAsStream("/code.db"));
Enumeration e = p.keys();
while (e.hasMoreElements()) {
String n = (String) e.nextElement();
String v = p.getProperty(n);
codes.put(v, n);
}
}
public static ImageParser getInstance() {
return SingletonHolder.instance;
}
public String parse(Image src) throws InterruptedException {
String[] codes = Gather.gather(src);
StringBuilder sb = new StringBuilder();
for (String s : codes) {
sb.append(this.codes.get(s));
}
return sb.toString();
}
}
最后就是如何來調(diào)用這個 ImageParser ，看它的一個單元測試就明白了：
/**
* Created on 2007-11-22 下午11:18:17
*/
import static org.junit.Assert.assertEquals;
import java.io.File;
import java.io.FilenameFilter;
import java.io.IOException;
import javax.imageio.ImageIO;
import org.apache.commons.io.FilenameUtils;
import org.junit.Test;
/**
* @author sutra
*
*/
public class ImageParserTest {
/**
* {@link ImageParser#parse(java.awt.Image)} 的測試方法。
*
* @throws IOException
* @throws InterruptedException
*/
@Test
public void testParse() throws InterruptedException, IOException {
File bmpDir = new File("src/main/bmp/");
File[] bmps = bmpDir.listFiles(new FilenameFilter() {
public boolean accept(File dir, String name) {
return "bmp".equalsIgnoreCase(FilenameUtils.getExtension(name));
}
});
for (File bmp : bmps) {
assertEquals(FilenameUtils.getBaseName(bmp.getName()), ImageParser
.getInstance().parse(ImageIO.read(bmp)));
}
}
}
這樣簡單的驗(yàn)證碼還存在嗎？存在的，確實(shí)存在的，有些程序員根本就沒有理解驗(yàn)證碼的目的，也許他只不過是看人家弄一個他也弄一個。這樣的程序員存在嗎？存在的，確實(shí)存在的，而且必將永遠(yuǎn)存在下去。
或者他弄個簡單的驗(yàn)證碼的目的就是為了讓某些人去識別。
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