java:均值哈希实现图像内容相似度比较

雨点打透心脏的1/2处 2022-06-15 23:27 243阅读 0赞

这阵子发现我的图像数据库中有不少内容一样的图像需要剔除，这些内容一样的图像可能尺寸不一样，通道数也可能不一样(灰度/彩色)，如下三张图内容完全一样，只是亮度或色彩通道数不同，  
![这里写图片描述][SouthEast]![这里写图片描述][SouthEast 1]![这里写图片描述][SouthEast 2]  
于是想到了用google或baidu的识图功能所用到的“感知哈希算法”来搜索数据库内容一样的图像。  
通过这篇文章搞清楚了“感知哈希算法”的基本原理，  
[《三种基于感知哈希算法的相似图像检索技术》][Link 1]，发现原理很简单，很适合我等粗人，呵呵，于是在java下实现了这个算法的代码 ：

# java实现 #

package net.gdface.image;
    
    import java.awt.Graphics;
    import java.awt.Image;
    import java.awt.color.ColorSpace;
    import java.awt.image.BufferedImage;
    import java.awt.image.ColorConvertOp;
    import java.util.Arrays;
    
    /**
     * 均值哈希实现图像指纹比较
     * @author guyadong
     *
     */
    public final class FingerPrint {
        
        /**
         * 图像指纹的尺寸,将图像resize到指定的尺寸，来计算哈希数组 
         */
        private static final int HASH_SIZE=16;
        /**
         * 保存图像指纹的二值化矩阵
         */
        private final byte[] binaryzationMatrix;
        public FingerPrint(byte[] hashValue) {
            if(hashValue.length!=HASH_SIZE*HASH_SIZE)
                throw new IllegalArgumentException(String.format("length of hashValue must be %d",HASH_SIZE*HASH_SIZE ));
            this.binaryzationMatrix=hashValue;
        }
        public FingerPrint(String hashValue) {
            this(toBytes(hashValue));
        }
        public FingerPrint (BufferedImage src){
            this(hashValue(src));
        }
        private static byte[] hashValue(BufferedImage src){
            BufferedImage hashImage = resize(src,HASH_SIZE,HASH_SIZE);
            byte[] matrixGray = (byte[]) toGray(hashImage).getData().getDataElements(0, 0, HASH_SIZE, HASH_SIZE, null); 
            return  binaryzation(matrixGray);
        }
        /**
         * 从压缩格式指纹创建{@link FingerPrint}对象
         * @param compactValue
         * @return
         */
        public static FingerPrint createFromCompact(byte[] compactValue){
            return new FingerPrint(uncompact(compactValue));
        }
    
        public static boolean validHashValue(byte[] hashValue){
            if(hashValue.length!=HASH_SIZE)
                return false;
            for(byte b:hashValue){
                if(0!=b&&1!=b)return false;         
            }
            return true;
        }
        public static boolean validHashValue(String hashValue){
            if(hashValue.length()!=HASH_SIZE)
                return false;
            for(int i=0;i<hashValue.length();++i){
                if('0'!=hashValue.charAt(i)&&'1'!=hashValue.charAt(i))return false;         
            }
            return true;
        }
        public byte[] compact(){
            return compact(binaryzationMatrix);
        }
    
        /**
         * 指纹数据按位压缩
         * @param hashValue
         * @return
         */
        private static byte[] compact(byte[] hashValue){
            byte[] result=new byte[(hashValue.length+7)>>3];
            byte b=0;
            for(int i=0;i<hashValue.length;++i){
                if(0==(i&7)){
                    b=0;
                }
                if(1==hashValue[i]){
                    b|=1<<(i&7);
                }else if(hashValue[i]!=0)
                    throw new IllegalArgumentException("invalid hashValue,every element must be 0 or 1");
                if(7==(i&7)||i==hashValue.length-1){
                    result[i>>3]=b;
                }
            }
            return result;
        }
    
        /**
         * 压缩格式的指纹解压缩
         * @param compactValue
         * @return
         */
        private static byte[] uncompact(byte[] compactValue){
            byte[] result=new byte[compactValue.length<<3];
            for(int i=0;i<result.length;++i){
                if((compactValue[i>>3]&(1<<(i&7)))==0)
                    result[i]=0;
                else
                    result[i]=1;
            }
            return result;      
        }
        /**
         * 字符串类型的指纹数据转为字节数组
         * @param hashValue
         * @return
         */
        private static byte[] toBytes(String hashValue){
            hashValue=hashValue.replaceAll("\\s", "");
            byte[] result=new byte[hashValue.length()];
            for(int i=0;i<result.length;++i){
                char c = hashValue.charAt(i);
                if('0'==c)
                    result[i]=0;
                else if('1'==c)
                    result[i]=1;
                else
                    throw new IllegalArgumentException("invalid hashValue String");
            }
            return result;
        }
        /**
         * 缩放图像到指定尺寸
         * @param src
         * @param width
         * @param height
         * @return
         */
        private static BufferedImage resize(Image src,int width,int height){
            BufferedImage result = new BufferedImage(width, height,  
                    BufferedImage.TYPE_3BYTE_BGR); 
             Graphics g = result.getGraphics();
             try{
                 g.drawImage(src.getScaledInstance(width, height, Image.SCALE_SMOOTH), 0, 0, null);
             }finally{
                 g.dispose();
             }
            return result;      
        }
        /**
         * 计算均值
         * @param src
         * @return
         */
        private static  int mean(byte[] src){
            long sum=0;
            // 将数组元素转为无符号整数
            for(byte b:src)sum+=(long)b&0xff;
            return (int) (Math.round((float)sum/src.length));
        }
        /**
         * 二值化处理
         * @param src
         * @return
         */
        private static byte[] binaryzation(byte[]src){
            byte[] dst = src.clone();
            int mean=mean(src);
            for(int i=0;i<dst.length;++i){
                // 将数组元素转为无符号整数再比较
                dst[i]=(byte) (((int)dst[i]&0xff)>=mean?1:0);
            }
            return dst;
    
        }
        /**
         * 转灰度图像
         * @param src
         * @return
         */
        private static BufferedImage toGray(BufferedImage src){
            if(src.getType()==BufferedImage.TYPE_BYTE_GRAY){
                return src;
            }else{
                // 图像转灰
                BufferedImage grayImage = new BufferedImage(src.getWidth(), src.getHeight(),  
                        BufferedImage.TYPE_BYTE_GRAY);
                new ColorConvertOp(ColorSpace.getInstance(ColorSpace.CS_GRAY), null).filter(src, grayImage);
                return grayImage;       
            }
        }
    
        @Override
        public String toString() {
            return toString(true);
        }
        /**
         * @param multiLine 是否分行
         * @return
         */
        public String toString(boolean multiLine) {
            StringBuffer buffer=new StringBuffer();
            int count=0;
            for(byte b:this.binaryzationMatrix){
                buffer.append(0==b?'0':'1');
                if(multiLine&&++count%HASH_SIZE==0)
                    buffer.append('\n');
            }
            return buffer.toString();
        }
        @Override
        public boolean equals(Object obj) {
            if(obj instanceof FingerPrint){
                return Arrays.equals(this.binaryzationMatrix,((FingerPrint)obj).binaryzationMatrix);
            }else
                return super.equals(obj);
        }
    
        /**
         * 与指定的压缩格式指纹比较相似度
         * @param compactValue
         * @return
         * @see #compare(FingerPrint)
         */
        public float compareCompact(byte[] compactValue){
            return compare(createFromCompact(compactValue));
        }
        /**
         * @param hashValue
         * @return
         * @see #compare(FingerPrint)
         */
        public float compare(String hashValue){
            return compare(new FingerPrint(hashValue));
        }
        /**
         * 与指定的指纹比较相似度
         * @param hashValue
         * @return
         * @see #compare(FingerPrint)
         */
        public float compare(byte[] hashValue){
            return compare(new FingerPrint(hashValue));
        }
        /**
         * 与指定图像比较相似度
         * @param image2
         * @return
         * @see #compare(FingerPrint)
         */
        public float compare(BufferedImage image2){
            return compare(new FingerPrint(image2));
        }
        /**
         * 比较指纹相似度
         * @param src
         * @return 
         * @see #compare(byte[], byte[])
         */
        public float compare(FingerPrint src){
            if(src.binaryzationMatrix.length!=this.binaryzationMatrix.length)
                throw new IllegalArgumentException("length of hashValue is mismatch");
            return compare(binaryzationMatrix,src.binaryzationMatrix);
        }
        /**
         * 判断两个数组相似度，数组长度必须一致否则抛出异常
         * @param f1
         * @param f2
         * @return 返回相似度(0.0~1.0)
         */
        private static float compare(byte[] f1,byte[] f2){
            if(f1.length!=f2.length)
                throw new IllegalArgumentException("mismatch FingerPrint length");
            int sameCount=0;
            for(int i=0;i<f1.length;++i){
                if(f1[i]==f2[i])++sameCount;
            }
            return (float)sameCount/f1.length;
        }
        public static float compareCompact(byte[] f1,byte[] f2){
            return compare(uncompact(f1),uncompact(f2));
        }
        public static float compare(BufferedImage image1,BufferedImage image2){
            return new FingerPrint(image1).compare(new FingerPrint(image2));
        }
    }

# 调用示例 #

junit测试代码

package test;
    
    import java.io.File;
    import java.io.IOException;
    
    import javax.imageio.ImageIO;
    
    import org.junit.Test;
    import net.gdface.image.FingerPrint;
    import net.gdface.image.NotImage;
    import net.gdface.image.UnsupportedFormat;
    
    public class TestFingerPrint {
        
    
        @Test
        public void testCompare() throws IOException{
            FingerPrint fp1 = new FingerPrint(ImageIO.read(new File("d:\\tmp\\he049-black.jpg")));
            FingerPrint fp2 =new FingerPrint(ImageIO.read(new File("d:\\tmp\\he049-gray.jpg")));
            System.out.println(fp1.toString(true));
            System.out.printf("sim=%f",fp1.compare(fp2));
        }
    }

[SouthEast]: https://img-blog.csdn.net/20170429151010067?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvMTBrbQ==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast
[SouthEast 1]: https://img-blog.csdn.net/20170429150957020?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvMTBrbQ==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/SouthEast
[SouthEast 2]: /images/20220616/994ac3df4a7f46e890950354889dc699.png
[Link 1]: http://www.tuicool.com/articles/6fm6ze