感知哈希算法对比图片相似度

package com.willson.common.utils;

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.color.ColorSpace;
import java.awt.image.BufferedImage;
import java.awt.image.ColorConvertOp;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;

/**
 * 比较两张图片的相似度
 * 感知哈希算法
 *
 */
public class ImageContrastUtil {
    // 对比方法
    public static Double imageComparison(InputStream sampleInputStream,InputStream contrastInputStream ) throws IOException {
        //获取灰度像素的比较数组
        int[] photoArrayTwo = getPhotoArray(contrastInputStream);
        int[] photoArrayOne = getPhotoArray(sampleInputStream);

        // 获取两个图的汉明距离
        int hammingDistance = getHammingDistance(photoArrayOne, photoArrayTwo);
        // 通过汉明距离计算相似度，取值范围 [0.0, 1.0]
        double similarity = calSimilarity(hammingDistance);

        //返回相似精度
        return  similarity;
    }

    // 将任意Image类型图像转换为BufferedImage类型，方便后续操作
    public static BufferedImage convertToBufferedFrom(Image srcImage) {
        BufferedImage bufferedImage = new BufferedImage(srcImage.getWidth(null),
                srcImage.getHeight(null), BufferedImage.TYPE_INT_ARGB);
        Graphics2D g = bufferedImage.createGraphics();
        g.drawImage(srcImage, null, null);
        g.dispose();
        return bufferedImage;
    }

    // 转换至灰度图
    public static BufferedImage toGrayscale(Image image) {
        BufferedImage sourceBuffered = convertToBufferedFrom(image);
        ColorSpace cs = ColorSpace.getInstance(ColorSpace.CS_GRAY);
        ColorConvertOp op = new ColorConvertOp(cs, null);
        BufferedImage grayBuffered = op.filter(sourceBuffered, null);
        return grayBuffered;
    }

    // 缩放至32x32像素缩略图
    public static Image scale(Image image) {
        image = image.getScaledInstance(32, 32, Image.SCALE_SMOOTH);
        return image;
    }

    // 获取像素数组
    public static int[] getPixels(Image image) {
        int width = image.getWidth(null);
        int height = image.getHeight(null);
        int[] pixels = convertToBufferedFrom(image).getRGB(0, 0, width, height,
                null, 0, width);
        return pixels;
    }

    // 获取灰度图的平均像素颜色值
    public static int getAverageOfPixelArray(int[] pixels) {
        Color color;
        long sumRed = 0;
        for (int i = 0; i < pixels.length; i++) {
            color = new Color(pixels[i], true);
            sumRed += color.getRed();
        }
        int averageRed = (int) (sumRed / pixels.length);
        return averageRed;
    }

    // 获取灰度图的像素比较数组（平均值的离差）
    public static int[] getPixelDeviateWeightsArray(int[] pixels, final int averageColor) {
        Color color;
        int[] dest = new int[pixels.length];
        for (int i = 0; i < pixels.length; i++) {
            color = new Color(pixels[i], true);
            dest[i] = color.getRed() - averageColor > 0 ? 1 : 0;
        }
        return dest;
    }

    // 获取两个缩略图的平均像素比较数组的汉明距离（距离越大差异越大）
    public static int getHammingDistance(int[] a, int[] b) {
        int sum = 0;
        for (int i = 0; i < a.length; i++) {
            sum += a[i] == b[i] ? 0 : 1;
        }
        return sum;
    }

    //获取灰度像素的比较数组
    public static int[] getPhotoArray(InputStream inputStream) throws IOException {
        Image image = ImageIO.read(inputStream);
//        Image image = ImageIO.read(imageFile);
        // 转换至灰度
        image = toGrayscale(image);
        // 缩小成32x32的缩略图
        image = scale(image);
        // 获取灰度像素数组
        int[] pixels = getPixels(image);
        // 获取平均灰度颜色
        int averageColor = getAverageOfPixelArray(pixels);
        // 获取灰度像素的比较数组（即图像指纹序列）
        pixels = getPixelDeviateWeightsArray(pixels, averageColor);

        return pixels;
    }

    // 通过汉明距离计算相似度
    public static double calSimilarity(int hammingDistance) {
        int length = 32 * 32;
        double similarity = (length - hammingDistance) / (double) length;

        // 使用指数曲线调整相似度结果
        similarity = java.lang.Math.pow(similarity, 2);
        return similarity;
    }
}