java直方图文件相似度比较 指纹提取存储 不用javacv

要实现指纹提取并进行存储，可以使用Java自带的图像处理库ImageIO来读取图像文件，并使用Java自带的数据分析库Apache Commons Math来计算直方图和指纹，并将指纹存储在文件中。

以下是一个示例代码：

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import javax.imageio.ImageIO;
import org.apache.commons.math3.stat.descriptive.moment.Mean;
import org.apache.commons.math3.stat.descriptive.summary.Sum;

public class FingerprintExtract {
    public static void main(String[] args) throws IOException {
        // 读取图像文件
        BufferedImage img = ImageIO.read(new File("image.jpg"));

        // 计算直方图
        int[] hist = calcHistogram(img);

        // 计算指纹
        int[] fingerprint = calcFingerprint(hist);

        // 存储指纹
        saveFingerprint(fingerprint, "fingerprint.txt");
    }

    private static int[] calcHistogram(BufferedImage img) {
        int[] hist = new int[256];
        for (int y = 0; y < img.getHeight(); y++) {
            for (int x = 0; x < img.getWidth(); x++) {
                int pixel = img.getRGB(x, y);
                int r = (pixel >> 16) & 0xff;
                int g = (pixel >> 8) & 0xff;
                int b = pixel & 0xff;
                int gray = (r + g + b) / 3;
                hist[gray]++;
            }
        }
        return hist;
    }

    private static int[] calcFingerprint(int[] hist) {
        int[] fingerprint = new int[64];
        double[] histNorm = normalize(hist);
        for (int i = 0; i < fingerprint.length; i++) {
            int start = i * 4;
            double max = Double.NEGATIVE_INFINITY;
            int maxIndex = -1;
            for (int j = start; j < start + 4; j++) {
                if (histNorm[j] > max) {
                    max = histNorm[j];
                    maxIndex = j;
                }
            }
            fingerprint[i] = maxIndex;
        }
        return fingerprint;
    }

    private static double[] normalize(int[] hist) {
        double[] histNorm = new double[hist.length];
        int numPixels = hist.length;
        Mean mean = new Mean();
        double histMean = mean.evaluate(hist);
        for (int i = 0; i < hist.length; i++) {
            histNorm[i] = hist[i] / (double) numPixels - histMean;
        }
        return histNorm;
    }

    private static void saveFingerprint(int[] fingerprint, String filename) throws IOException {
        PrintWriter writer = new PrintWriter(filename);
        for (int i = 0; i < fingerprint.length; i++) {
            writer.print(fingerprint[i]);
            if (i < fingerprint.length - 1) {
                writer.print(",");
            }
        }
        writer.close();
    }
}

该代码读取一个图像文件，计算它的直方图和指纹，并将指纹存储在文件中。其中，`calcHistogram`方法用于计算直方图，`calcFingerprint`方法用于计算指纹，`normalize`方法用于将直方图归一化，以便计算指纹。`saveFingerprint`方法用于将指纹存储在文件中。指纹用逗号分隔，并存储在一个文本文件中。