验证码识别作为图像分类的一种特殊形式,可以通过深度学习模型实现自动解码。虽然大多数教程使用 Python 编写,但本文将展示如何使用 Java 和 DJL(Deep Java Library) 实现一个完整的验证码识别系统。
1. 准备工作
确保你的开发环境满足以下条件:
- JDK 8 以上
- Maven 3.x
- 已安装 Python,用于生成训练数据和训练模型(建议使用 PyTorch)
添加 Maven 依赖
<dependencies>
<dependency>
<groupId>ai.djl</groupId>
<artifactId>api</artifactId>
<version>0.25.0</version>
更多内容访问ttocr.com或联系1436423940 </dependency>
<dependency>
<groupId>ai.djl.pytorch</groupId>
<artifactId>pytorch-engine</artifactId>
<version>0.25.0</version>
</dependency>
<dependency>
<groupId>ai.djl.pytorch</groupId>
<artifactId>pytorch-model-zoo</artifactId>
<version>0.25.0</version>
</dependency>
</dependencies>
2. 模型准备(Python)
训练部分推荐使用 PyTorch,然后保存为 TorchScript 格式:
# train_and_export.py
import torch
import torch.nn as nn
import torchvision.transforms as transforms
from captcha.image import ImageCaptcha
import string
import random
from PIL import Image
# 模型定义略(CNN + LSTM)
# 假设你已经训练好一个模型
# 保存为 TorchScript
example_input = torch.randn(1, 3, 60, 160)
traced = torch.jit.trace(model, example_input)
traced.save("captcha_model.pt")
3. 加载模型并预测(Java)
import ai.djl.Model;
import ai.djl.inference.Predictor;
import ai.djl.modality.cv.ImageFactory;
import ai.djl.modality.cv.transform.*;
import ai.djl.ndarray.*;
import ai.djl.ndarray.types.Shape;
import ai.djl.translate.*;
import ai.djl.translate.TranslateException;
import java.io.IOException;
import java.nio.file.Paths;
import java.util.*;
public class CaptchaRecognizer {
private static final String[] CHARS = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ".split("");
public static void main(String[] args) throws IOException, TranslateException {
// 加载模型
Model model = Model.newInstance("captcha");
model.load(Paths.get("models")); // 模型路径
// 加载图片
var image = ImageFactory.getInstance().fromFile(Paths.get("captcha_samples/B8ZK_0.png"));
// 构建 Translator
Translator<ai.djl.modality.cv.Image, String> translator = new Translator<>() {
@Override
public NDList processInput(TranslatorContext ctx, ai.djl.modality.cv.Image input) {
NDArray array = input.toNDArray(ctx.getNDManager());
array = array.transpose(2, 0, 1).div(255f);
array = array.expandDims(0); // [1, 3, H, W]
return new NDList(array);
}
@Override
public String processOutput(TranslatorContext ctx, NDList list) {
NDArray output = list.get(0); // [1, 4, 36]
int[] shape = output.getShape().getShape();
StringBuilder sb = new StringBuilder();
for (int i = 0; i < shape[1]; i++) {
NDArray charLogits = output.get(0).get(i); // 第i位字符的预测
int index = charLogits.argMax().getInt();
sb.append(CHARS[index]);
}
return sb.toString();
}
@Override
public Batchifier getBatchifier() {
return null;
}
};
// 创建预测器
try (Predictor<ai.djl.modality.cv.Image, String> predictor = model.newPredictor(translator)) {
String result = predictor.predict(image);
System.out.println("识别结果: " + result);
}
}
}