以图搜图，涉及两大功能：1、提取图像特征向量。2、相似向量检索。

第一个功能我通过编写pytorch模型并在java端借助djl调用实现，第二个功能通过elasticsearch7.6.2的dense_vector、cosineSimilarity实现。

一、准备模型

创建demo.py，输入代码，借助resnet提取图像特征

import torch
import torch.nn as nn
import torchvision.models as models

class ImageFeatureExtractor(nn.Module):
    def __init__(self):
        super(ImageFeatureExtractor, self).__init__()
        self.resnet = models.resnet50(pretrained=True)
        #最终输出维度1024的向量，下文elastic search要设置dims为1024
        self.resnet.fc = nn.Linear(2048, 1024)

    def forward(self, x):
        x = self.resnet(x)
        return x

if __name__ == '__main__':
    model = ImageFeatureExtractor()
    model.eval()
    #根据模型随便创建一个输入
    input = torch.rand([1, 3, 224, 224])
    output = model(input)
    #以这种方式保存
    script = torch.jit.trace(model, input)
    script.save("model.pt")

保存好的model.pt文件放入java项目的resources中，可以在java中引入Deep-Java-Library来调用

二、创建Java项目

创建项目，引入djl和elasticsearch的依赖

<dependency>
            <groupId>ai.djl.pytorch</groupId>
            <artifactId>pytorch-engine</artifactId>
            <version>0.19.0</version>
        </dependency>
        <dependency>
            <groupId>ai.djl.pytorch</groupId>
            <artifactId>pytorch-native-cpu</artifactId>
            <version>1.10.0</version>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>ai.djl.pytorch</groupId>
            <artifactId>pytorch-jni</artifactId>
            <version>1.10.0-0.19.0</version>
        </dependency>
        <dependency>
            <groupId>org.elasticsearch.client</groupId>
            <artifactId>elasticsearch-rest-high-level-client</artifactId>
            <version>7.6.2</version>
        </dependency>

然后随便从网上下载点图片，比如猫5张图狗5张图什么的，放到项目"resources/随便" 路径下，一会要提取他们的特征向量并上传至elasticsearch

三、es创建文档

需要在elastic search中创建一个新文档。localhost:9200/isi   (img search img)

PUT /isi
{
  "mappings": {
    "properties": {
      "vector": {
        "type": "dense_vector",
        "dims": 1024
      },
      "url" : {
        "type" : "keyword"
      },
      "user_id": {
          "type": "keyword"
      }
    }
  }
}

完成下文上传操作后测试搜索（params中queryVector为随便选了个图像提取的特征向量）：

POST /isi/_search
{
  "query": {
    "function_score": {
      "query": {
        "match_all": {}
      },
      "script_score": {
        "script": {
          "source": "cosineSimilarity(params.queryVector, 'vector') ",
          "params": {
            "queryVector": [-0.21950562, 0.0979692, 0.30605257, -0.04246464, 0.3086218, 0.2133326, -0.13531154, 0.16382562, 0.2505685, 0.35654455, 0.50346404, -0.2031727, -0.4501943, 0.23117387, 0.39451313, 0.044487886, -0.11032343, 0.47252116, 0.24667346, -0.2052311, -0.10872754, 0.22328046, 0.13366169, -0.5555884, 0.23139203, 0.024292288, 0.3071902, 0.23381571, -0.14484097, -0.80570614, 0.096950606, -0.034106746, 0.3221968, 0.35980088, -0.24408965, 0.10010342, 0.34878045, 0.25403115, 0.8813986, -0.23978959, -0.101492174, -0.34241566, -0.258092, 0.38593173, 0.24993907, -0.6891467, 0.5723483, -0.4987241, -0.46613082, 0.07435644, -0.32876882, 0.1923833, 0.41619772, 0.006919967, -0.35519657, -0.2463252, -0.07216969, -0.10412077, -0.3964988, -0.43174505, 0.6576338, -0.09753291, 0.058324523, -0.366405, -0.08003934, -0.41232625, -0.59834087, 0.35432702, -0.33971205, -0.695481, -0.38738084, -0.08746443, 0.37581405, 0.5092232, 0.26168102, 0.33873072, 0.3769325, 0.5525994, -0.018578911, 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          }
        }
      }
    }
  },
  "_source": ["url"],
  "size": 100
}

四、调用pytorch模型代码

创建Test类，copy一下我的，感兴趣可以去djl的官网学习更多内容。写完后，就可以获取“随便”文件夹中的图像的特征向量，上传到es里了。

package org.gwen;

import ai.djl.Device;
import ai.djl.Model;
import ai.djl.inference.Predictor;
import ai.djl.modality.cv.Image;
import ai.djl.modality.cv.ImageFactory;
import ai.djl.modality.cv.transform.Normalize;
import ai.djl.modality.cv.transform.Resize;
import ai.djl.modality.cv.transform.ToTensor;
import ai.djl.modality.cv.util.NDImageUtils;
import ai.djl.ndarray.NDArray;
import ai.djl.ndarray.NDList;
import ai.djl.ndarray.NDManager;
import ai.djl.translate.Transform;
import ai.djl.translate.Translator;
import ai.djl.translate.TranslatorContext;
import org.apache.http.HttpHost;
import org.elasticsearch.action.bulk.BulkRequest;
import org.elasticsearch.action.index.IndexRequest;
import org.elasticsearch.action.search.SearchRequest;
import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestClientBuilder;
import org.elasticsearch.client.RestHighLevelClient;
import org.elasticsearch.client.transport.TransportClient;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.common.xcontent.XContentType;
import org.elasticsearch.index.query.QueryBuilders;
import org.elasticsearch.index.query.ScriptQueryBuilder;
import org.elasticsearch.index.query.functionscore.FunctionScoreQueryBuilder;
import org.elasticsearch.index.query.functionscore.ScoreFunctionBuilders;
import org.elasticsearch.script.Script;
import org.elasticsearch.script.ScriptType;
import org.elasticsearch.search.SearchHit;
import org.elasticsearch.search.SearchHits;
import org.elasticsearch.search.builder.SearchSourceBuilder;
import org.gwen.entity.SearchResult;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.URI;
import java.net.URL;
import java.nio.file.Paths;
import java.util.*;

public class Test {

    private static final String INDEX = "isi";
    private static final int IMAGE_SIZE = 224;
    private static Model model; //模型
    private static Predictor<Image, float[]> predictor; //predictor.predict(input)相当于python中model(input)
    static {
        try {
            model = Model.newInstance("model");
            //这里的model.pt是上面代码展示的那种方式保存的
            model.load(Test.class.getClassLoader().getResourceAsStream("model.pt"));
            Transform resize = new Resize(IMAGE_SIZE);
            Transform toTensor = new ToTensor();
            Transform normalize = new Normalize(new float[]{0.485f, 0.456f, 0.406f}, new float[]{0.229f, 0.224f, 0.225f});
            //Translator处理输入Image转为tensor、输出转为float[]
            Translator<Image, float[]> translator = new Translator<Image, float[]>() {
                @Override
                public NDList processInput(TranslatorContext ctx, Image input) throws Exception {
                    NDManager ndManager = ctx.getNDManager();
                    System.out.println("input: " + input.getWidth() + ", " + input.getHeight());
                    NDArray transform = normalize.transform(toTensor.transform(resize.transform(input.toNDArray(ndManager))));
                    System.out.println(transform.getShape());
                    NDList list = new NDList();
                    list.add(transform);
                    return list;
                }
                @Override
                public float[] processOutput(TranslatorContext ctx, NDList ndList) throws Exception {
                    return ndList.get(0).toFloatArray();
                }
            };
            predictor = new Predictor<>(model, translator, Device.cpu(), true);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

五、es上传和搜索

上传：遍历每张图片，获取每张图片的特征，上传到es

搜索：获取输入图像的特征，创建SearchRequest在es中通过painless脚本进行余弦相似度对比检索。

首先创建SearchResult类表示es搜索的结果，包括图像url和相关度评分score

@Data
@AllArgsConstructor
public class SearchResult {
    private String url;
    private Float score;
}

然后在Test里实现upload和search

    public static void upload() throws Exception {
        RestHighLevelClient client = new RestHighLevelClient(
                RestClient.builder(new HttpHost("localhost", 9200, "http")));
        //批量上传请求
        BulkRequest bulkRequest = new BulkRequest(INDEX);
        File file = new File("C:\\Users\\Administrator\\IdeaProjects\\img_search_img\\src\\main\\resources\\随便");
        for (File listFile : file.listFiles()) {
            float[] vector = predictor.predict(ImageFactory.getInstance().fromInputStream(Test.class.getClassLoader().getResourceAsStream("随便/" + listFile.getName())));
            // 构建文档
            Map<String, Object> jsonMap = new HashMap<>();
            jsonMap.put("url", listFile.getAbsolutePath());
            jsonMap.put("vector", vector);
            jsonMap.put("user_id", "user123");
            IndexRequest request = new IndexRequest(INDEX).source(jsonMap, XContentType.JSON);
            bulkRequest.add(request);
        }
        client.bulk(bulkRequest, RequestOptions.DEFAULT);
        client.close();
    }

    //接收待搜索图片的inputstream，搜索与其相似的图片
    public static List<SearchResult> search(InputStream input) throws Throwable {
        float[] vector = predictor.predict(ImageFactory.getInstance().fromInputStream(input));
        System.out.println(Arrays.toString(vector));

        //展示k个结果
        int k = 100;
        // 连接Elasticsearch服务器
        RestHighLevelClient client = new RestHighLevelClient(
                RestClient.builder(new HttpHost("localhost", 9200, "http")));

        SearchRequest searchRequest = new SearchRequest(INDEX);
        Script script = new Script(
                ScriptType.INLINE,
                "painless",
                "cosineSimilarity(params.queryVector, doc['vector'])",
                Collections.singletonMap("queryVector", vector));

        FunctionScoreQueryBuilder functionScoreQueryBuilder = QueryBuilders.functionScoreQuery(
                QueryBuilders.matchAllQuery(),
                ScoreFunctionBuilders.scriptFunction(script));

        SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
        searchSourceBuilder.query(functionScoreQueryBuilder)
                .fetchSource(null, "vector") //不返回vector字段，太多了没用还耗时
                .size(k);

        searchRequest.source(searchSourceBuilder);

        SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);

        SearchHits hits = searchResponse.getHits();

        List<SearchResult> list = new ArrayList<>();
        for (SearchHit hit : hits) {
            // 处理搜索结果
            System.out.println(hit.toString());
            SearchResult result = new SearchResult((String) hit.getSourceAsMap().get("url"), hit.getScore());
            list.add(result);
        }

        client.close();
        return list;
    }

六、测试

@RestController
@CrossOrigin
public class SearchController {

    @PostMapping("search")
    public ResponseEntity search(MultipartFile file) {
        try {
            List<SearchResult> list = Test.search(file.getInputStream());
            return ResponseEntity.ok(list);
        } catch (Throwable e) {
            return ResponseEntity.status(400).body(null);
        }
    }
}

页面：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        body {
            background: url("/img/bg.jpg");
            background-attachment: fixed;
            background-size: 100% 100%;
        }
        body > div {
            width: 1000px;
            margin: 50px auto;
            padding: 10px 20px;
            border: 1px solid lightgray;
            border-radius: 20px;
            box-sizing: border-box;
            background: rgba(255, 255, 255, 0.7);
        }
        .upload {
            display: inline-block;
            width: 300px;
            height: 280px;
            border: 1px dashed lightcoral;
            vertical-align: top;
        }
        .upload .cover {
            width: 200px;
            height: 200px;
            margin: 10px 50px;
            border: 1px solid black;
            box-sizing: border-box;
            text-align: center;
            line-height: 200px;
            position: relative;
        }
        .upload img {
            width: 198px;
            height: 198px;
            position: absolute;
            left:0;
            top: 0;
        }
        .upload input {
            margin-left: 50px;
        }
        .upload button {
            width: 80px;
            height: 30px;
            margin-left: 110px;
        }
        .result-block {
            display:  inline-block;
            margin-left: 40px;
            border: 1px solid lightgray;
            border-radius: 10px;
            min-height: 500px;
            width: 600px;
        }
        .result-block h1 {
            text-align: center;
            margin-top: 100px;
        }
        .result {
            padding: 10px;
            cursor: pointer;
            display: inline-block;
        }
        .result:hover {
            background: rgb(240, 240, 240);
        }
        .result p {
            width: 110px;
            overflow: hidden;
            white-space: nowrap;
            text-overflow: ellipsis;
        }
        .result img {
            width: 160px;
            height: 160px;
        }
        .result .prob {
            color: rgb(37, 147, 60)
        }
    </style>
    <script src="js/jquery-3.6.0.js"></script>
</head>
<body>
<div>
    <div class="upload">
        <div class="cover">
            请选择图片
            <img id="image" src=""/>
        </div>
        <input id="file" type="file">
    </div>
    <div class="result-block">
        <h1>请选择图片</h1>
    </div>
</div>
    <ul id="box">

    </ul>
<script>
    var file = $('#file')
    file.change(function () {
        let f = this.files[0]
        let index = f.name.lastIndexOf('.')
        let fileText = f.name.substring(index,f.name.length)
        let ext = fileText.toLowerCase() //文件类型
        console.log(ext)
        if(ext != '.png' && ext != '.jpg' && ext != '.jpeg'){
            alert('系统仅支持 JPG、PNG、JPEG 格式的图片，请您调整格式后重新上传')
            return
        }
        $('.result-block').empty().append($('<h1>正在识别中...</h1>'))
        $("#image").attr("src",getObjectURL(f));
        let formData = new FormData()
        formData.append('file',f)
        $.ajax({
            url: 'http://localhost:8080/search',
            method: 'post',
            data: formData,
            processData: false,
            contentType: false,
            success: res => {
                console.log('shibie', res)
                $('.result-block').empty()
                for (let item of res) {
                    console.log(item)
                    let html = `<div class="result">
                                    <img src="file:///${item.url}"/>
                                    <div style="display: inline-block;vertical-align: top">
                                        <p class="prob">得分：${item.score.toFixed(4)}</p>
                                    </div>
                                </div>`
                    $('.result-block').append($(html))
                }

            }
        })
    });
    $('#button').click(function(e) {
        var file = $('#file')[0].files[0] //单个
        console.log(file)
    })
    function getObjectURL(file) {
        var url = null;
        if (window.createObjcectURL != undefined) {
            url = window.createOjcectURL(file);
        } else if (window.URL != undefined) {
            url = window.URL.createObjectURL(file);
        } else if (window.webkitURL != undefined) {
            url = window.webkitURL.createObjectURL(file);
        }
        return url;
    }
    function detect() {

    }
</script>
</body>
</html>