php 感知哈希算法实现图片相似度对比

感知哈希的优点是简单快速，不受图片大小缩放的影响，缺点是图片的内容不能变更。实际应用中，往往采用更强大的pHash算法和SIFT算法，它们能够识别图片的变形。只要变形程度不超过25%，它们就能匹配原图。

<?php
// count < =5 匹配最相似；count > 10 两张不同的图片 实际应用中可自己调节count的值
class ImageHash
{

    const FILE_NOT_FOUND = '-1';

    const FILE_EXTNAME_ILLEGAL = '-2';

    public static function run($src1, $src2)
    {

        static $self;

        if (!$self) $self = new static;

        if (!is_file($src1) || !is_file($src2)) exit(self::FILE_NOT_FOUND);

        $hash1 = $self->getHashValue($src1);

        $hash2 = $self->getHashValue($src2);

        if (strlen($hash1) !== strlen($hash2)) return false;

        $count = 0;

        $len = strlen($hash1);

        for ($i = 0; $i < $len; $i++) if ($hash1[$i] !== $hash2[$i]) $count++;

        return $count <= 5 ? true : false;
    }

    public function getImage($file)
    {

        $extname = pathinfo($file, PATHINFO_EXTENSION);

        if (!in_array($extname, ['jpg', 'jpeg', 'png', 'gif'])) exit(self::FILE_EXTNAME_ILLEGAL);

        $img = call_user_func('imagecreatefrom' . ($extname == 'jpg' ? 'jpeg' : $extname), $file);

        return $img;
    }

    public function getHashValue($file)
    {

        $w = 8;

        $h = 8;

        $img = imagecreatetruecolor($w, $h);

        list($src_w, $src_h) = getimagesize($file);

        $src = $this->getImage($file);

        imagecopyresampled($img, $src, 0, 0, 0, 0, $w, $h, $src_w, $src_h);

        imagedestroy($src);

        $total = 0;

        $array = array();

        for ($y = 0; $y < $h; $y++) {

            for ($x = 0; $x < $w; $x++) {

                $gray = (imagecolorat($img, $x, $y) >> 8) & 0xFF;

                if (!isset($array[$y])) $array[$y] = array();

                $array[$y][$x] = $gray;

                $total += $gray;
            }
        }

        imagedestroy($img);

        $average = intval($total / ($w * $h * 2));

        $hash = '';

        for ($y = 0; $y < $h; $y++) {

            for ($x = 0; $x < $w; $x++) {

                $hash .= ($array[$y][$x] >= $average) ? '1' : '0';
            }
        }
        return $hash;
    }
}

var_dump(ImageHash::run(‘./1.png', ‘./psb.jpg'));

文章来源于：https://www.php.cn/php-weizijiaocheng-383488.html