基于MATLAB的验证码识别系统实现

一、系统架构设计

验证码识别流程分为四个核心模块：

1. 图像预处理：灰度化、二值化、去噪、字符分割
2. 特征提取：几何特征、纹理特征、HOG特征
3. 分类识别：模板匹配、机器学习、深度学习
4. 后处理优化：结果校正、格式校验

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二、基础版实现（Tesseract+预处理）

function code = basic_ocr(imagePath)
    % 图像预处理
    img = imread(imagePath);
    gray = rgb2gray(img);
    bw = imbinarize(gray);
    clean = medfilt2(bw, [3,3]);  % 中值滤波去噪
    
    % 字符分割（垂直投影法）
    verticalProj = sum(clean, 1);
    [peaks, locs] = findpeaks(verticalProj, 'MinPeakHeight', 2);
    charRegions = imcrop(clean, [locs(1),1,locs(end)-locs(1),size(clean,1)]);
    
    % 调用Tesseract OCR
    output = tempname;
    system(sprintf('tesseract "%s" "%s" -l eng -c tessedit_char_whitelist=0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ', ...
        charRegions, output));
    fid = fopen([output, '.txt']);
    code = fgetl(fid);
    fclose(fid);
    delete(output);
end

优化建议：

• 添加形态学操作：clean = imopen(clean, strel('disk',1))去除小噪点
• 字符间距调整：charRegions = adjustCharSpacing(clean)

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三、进阶版实现（CNN分类器）

%% 数据准备
[XTrain,YTrain] = load_captcha_dataset('captcha_train.mat');  % 自定义数据集加载
layers = [
    imageInputLayer([30 100 1])
    convolution2dLayer(3,16,'Padding','same')
    reluLayer
    maxPooling2dLayer(2,'Stride',2)
    convolution2dLayer(3,32,'Padding','same')
    reluLayer
    maxPooling2dLayer(2,'Stride',2)
    fullyConnectedLayer(36)  % 0-9+A-Z共36类
    softmaxLayer
    classificationLayer];

%% 模型训练
options = trainingOptions('sgdm',...
    'MaxEpochs',10,...
    'MiniBatchSize',32,...
    'InitialLearnRate',0.001);
net = trainNetwork(XTrain,YTrain,layers,options);

%% 验证码识别
function code = cnn_ocr(imagePath)
    img = imread(imagePath);
    processed = preprocess(img);  % 预处理函数
    resized = imresize(processed, [30,100]);
    X = im2single(resized);
    label = classify(net,X);
    code = decodeLabel(label);  % 标签到字符转换
end

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四、预处理技术详解

1. 灰度化与二值化

   gray = rgb2gray(img);
   level = graythresh(gray);  % Otsu算法自动阈值
   bw = imbinarize(gray, level);
   

2. 去噪优化 中值滤波：medfilt2(bw, [3,3]) 形态学去噪：bwareaopen(bw, 50)

3. 字符分割算法

   % 水平投影分割
   horizontalProj = sum(bw, 2);
   rowIndices = find(horizontalProj > 0);
   charHeight = rowIndices(end) - rowIndices(1);
   

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五、深度学习

1. 数据增强

   augmentedData = imageDataAugmenter(...
       'RandRotation', [-10,10],...
       'RandXReflection', true,...
       'RandYReflection', true);
   

2. 迁移学习

   net = alexnet;
   layers(1) = imageInputLayer([30 100 1]);  % 修改输入层
   net = trainNetwork(XTrain,YTrain,layers,options);
   

3. 损失函数优化

   options = trainingOptions('adam',...
       'L2Regularization',0.001,...
       'Shuffle','every-epoch');
   

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六、完整工程实现步骤

1. 环境配置 安装Computer Vision Toolbox 下载Tesseract OCR并配置路径

2. GUI界面开发

   function gui_demo()
       f = figure('MenuBar','none','ToolBar','none');
       uicontrol('Style','pushbutton','String','选择图片',...
           'Callback',{@selectImage,callback});
       uicontrol('Style','text','String','识别结果:');
   end
   

3. 性能评估

   accuracy = sum(predicted == trueLabels)/numel(trueLabels);
   confusionchart(trueLabels, predicted);
   

参考代码 matlab 验证码识别程序 www.youwenfan.com/contentcnm/63638.html

七、典型应用场景

1. 验证码批量破解 处理万级验证码数据集时，GPU加速可提升8倍速度
2. 自动化测试系统 集成到Selenium实现登录自动化
3. 文档数字化 处理扫描件中的印刷体验证码