PHP image similarity code example-PHP Tutorial-php.cn

PHP image similarity code example

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Release： 2016-07-25 08:52:06

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/**
* Image similarity comparison
*
* @version $Id: ImageHash.php 4429 2012-04-17 13:20:31Z jax $
* @authorjax.hu
* www.osxue.com
*//Sample_1
*$aHash = ImageHash::hashImageFile('wsz.11.jpg');
*$bHash = ImageHash::hashImageFile('wsz.12.jpg');
*var_dump(ImageHash::isHashSimilar($aHash, $bHash));
*
*//Sample_2
*var_dump(ImageHash::isImageFileSimilar('wsz.11.jpg', 'wsz.12.jpg'));
*
*/
class ImageHash {
/**Sampling rate 1~10
* @access public
* @staticvar int
**/
public static $rate = 2;
/**Similarity allowed value 0~64
* @access public
* @staticvar int
**/
public static $similarity = 80;
/**The opening function corresponding to the image type
* @access private
* @staticvar string
**/
private static $_createFunc = array(
IMAGETYPE_GIF =>'imageCreateFromGIF',
IMAGETYPE_JPEG=>'imageCreateFromJPEG',
IMAGETYPE_PNG =>'imageCreateFromPNG',
IMAGETYPE_BMP =>'imageCreateFromBMP',
IMAGETYPE_WBMP=>'imageCreateFromWBMP',
IMAGETYPE_XBM =>'imageCreateFromXBM',
);
/**Create an image from a file
* @param string $filePath file address path
* @return resource When the image is successfully opened, the image resource ID is passed, and if it fails, it is false
**/
public static function createImage($filePath){
if(!file_exists($filePath)){ return false; }
/*判断文件类型是否可以开启*/
$type = exif_imagetype($filePath);
if(!array_key_exists($type,self::$_createFunc)){ return false; }
$func = self::$_createFunc[$type];
if(!function_exists($func)){ return false; }
return $func($filePath);
}
/**hash image
* @param resource $src image resource ID
* @return string image hash value, false on failure
**/
public static function hashImage($src){
if(!$src){ return false; }
/*缩小图片尺寸*/
$delta = 8 * self::$rate;
$img = imageCreateTrueColor($delta,$delta);
imageCopyResized($img,$src, 0,0,0,0, $delta,$delta,imagesX($src),imagesY($src));
/*计算图片灰阶值*/
$grayArray = array();
for ($y=0; $y<$delta; $y++){
for ($x=0; $x<$delta; $x++){
$rgb = imagecolorat($img,$x,$y);
$col = imagecolorsforindex($img, $rgb);
$gray = intval(($col['red']+$col['green']+$col['blue'])/3)& 0xFF;
$grayArray[] = $gray;
}
}
imagedestroy($img);
/*计算所有像素的灰阶平均值*/
$average = array_sum($grayArray)/count($grayArray);
/*计算 hash 值*/
$hashStr = '';
foreach ($grayArray as $gray){
$hashStr .= ($gray>=$average) ? '1' : '0';
}
return $hashStr;
}
/**hash image file
* @param string $filePath file address path
* @return string image hash value, false on failure
**/
public static function hashImageFile($filePath){
$src = self::createImage($filePath);
$hashStr = self::hashImage($src);
imagedestroy($src);
return $hashStr;
}
/**Compare two hash values to see if they are similar
* @param string $aHash The hash value of picture A
* @param string $bHash The hash value of picture B
* @return bool If the pictures are similar, true will be passed, otherwise false
**/
public static function isHashSimilar($aHash, $bHash){
$aL = strlen($aHash); $bL = strlen($bHash);
if ($aL !== $bL){ return false; }
/*计算容许落差的数量*/
$allowGap = $aL*(100-self::$similarity)/100;
/*计算两个 hash 值的汉明距离*/
$distance = 0;
for($i=0; $i<$aL; $i++){
if ($aHash{$i} !== $bHash{$i}){ $distance++; }
}
return ($distance<=$allowGap) ? true : false;
}
/**Compare two image files to see if they are similar
* @param string $aHash The path of image A
* @param string $bHash The path of image B
* @return bool When the images are similar, true is passed, otherwise false
**/
public static function isImageFileSimilar($aPath, $bPath){
$aHash = ImageHash::hashImageFile($aPath);
$bHash = ImageHash: :hashImageFile($bPath);
return ImageHash::isHashSimilar($aHash, $bHash);
}
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