NCBACK-34 add logic to find similar image in db

src/main/java/ru/soune/nocopy/service/ImageHashService.java

@@ -0,0 +1,154 @@
+package ru.soune.nocopy.service;
+
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.stereotype.Service;
+import ru.soune.nocopy.entity.file.FileEntity;
+import ru.soune.nocopy.entity.file.ImageHashEntity;
+import ru.soune.nocopy.repository.ImageHashRepository;
+
+import javax.imageio.ImageIO;
+import java.awt.*;
+import java.awt.image.BufferedImage;
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.time.LocalDateTime;
+import java.util.Arrays;
+
+@Service
+@RequiredArgsConstructor
+@Slf4j
+public class ImageHashService {
+
+    private final ImageHashRepository repository;
+
+    public void create(FileEntity file, Path imagePath) {
+        try {
+            long hash64 = computePhash64(imagePath);
+
+            int hi = high32(hash64);
+            int lo = low32(hash64);
+
+            ImageHashEntity entity = ImageHashEntity.builder()
+                    .file(file)
+                    .hash64Hi(hi)
+                    .hash64Lo(lo)
+                    .hashAlgorithm("PHASH64")
+                    .createdAt(LocalDateTime.now())
+                    .build();
+
+            repository.save(entity);
+        } catch (IOException e) {
+            throw new RuntimeException("Failed to compute image hash", e);
+        }
+    }
+
+    private long computePhash64(Path path) throws IOException {
+        try (InputStream is = Files.newInputStream(path)) {
+            BufferedImage image = ImageIO.read(is);
+            if (image == null) throw new IOException("Cannot read image file: " + path);
+
+            BufferedImage gray = toGrayScale(image);
+            BufferedImage resized = resizeImage(gray, 32, 32);
+
+            double[][] dct = applyDCT(resized);
+            double[][] topLeft = extractTopLeft8x8(dct);
+            double median = calculateMedian(topLeft, true);
+
+            return create64BitHashLong(topLeft, median);
+        }
+    }
+
+    private BufferedImage toGrayScale(BufferedImage image) {
+        BufferedImage gray = new BufferedImage(image.getWidth(), image.getHeight(), BufferedImage.TYPE_BYTE_GRAY);
+        Graphics2D g = gray.createGraphics();
+        g.drawImage(image, 0, 0, null);
+        g.dispose();
+        return gray;
+    }
+
+    private BufferedImage resizeImage(BufferedImage image, int width, int height) {
+        BufferedImage resized = new BufferedImage(width, height, BufferedImage.TYPE_BYTE_GRAY);
+        Graphics2D g = resized.createGraphics();
+        g.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
+        g.drawImage(image, 0, 0, width, height, null);
+        g.dispose();
+        return resized;
+    }
+
+    private double[][] applyDCT(BufferedImage image) {
+        int w = image.getWidth();
+        int h = image.getHeight();
+        double[][] pixels = new double[h][w];
+
+        for (int y = 0; y < h; y++) {
+            for (int x = 0; x < w; x++) {
+                int gray = image.getRGB(x, y) & 0xFF;
+                pixels[y][x] = gray;
+            }
+        }
+
+        double[][] dct = new double[h][w];
+        for (int u = 0; u < h; u++) {
+            double au = u == 0 ? 1.0 / Math.sqrt(h) : Math.sqrt(2.0 / h);
+            for (int v = 0; v < w; v++) {
+                double av = v == 0 ? 1.0 / Math.sqrt(w) : Math.sqrt(2.0 / w);
+                double sum = 0.0;
+                for (int x = 0; x < h; x++) {
+                    for (int y = 0; y < w; y++) {
+                        sum += pixels[x][y] *
+                                Math.cos((2 * x + 1) * u * Math.PI / (2.0 * h)) *
+                                Math.cos((2 * y + 1) * v * Math.PI / (2.0 * w));
+                    }
+                }
+                dct[u][v] = au * av * sum;
+            }
+        }
+        return dct;
+    }
+
+    private double[][] extractTopLeft8x8(double[][] dct) {
+        double[][] block = new double[8][8];
+        for (int i = 0; i < 8; i++) System.arraycopy(dct[i], 0, block[i], 0, 8);
+        return block;
+    }
+
+    private double calculateMedian(double[][] block, boolean excludeDC) {
+        double[] vals = new double[63];
+        int idx = 0;
+        for (int i = 0; i < 8; i++) {
+            for (int j = 0; j < 8; j++) {
+                if (i == 0 && j == 0 && excludeDC) continue;
+                vals[idx++] = block[i][j];
+            }
+        }
+        Arrays.sort(vals);
+        return (vals.length % 2 == 0) ?
+                (vals[vals.length / 2 - 1] + vals[vals.length / 2]) / 2.0 :
+                vals[vals.length / 2];
+    }
+
+    private long create64BitHashLong(double[][] block, double median) {
+        long hash = 0L;
+
+        for (int i = 0; i < 8; i++) {
+            for (int j = 0; j < 8; j++) {
+                if (i == 0 && j == 0) continue;
+                hash <<= 1;
+                if (block[i][j] > median) hash |= 1;
+            }
+        }
+
+        return hash;
+    }
+
+    private int high32(long hash64) {
+        return (int) (hash64 >>> 32);
+    }
+
+    private int low32(long hash64) {
+        return (int) hash64;
+    }
+}