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https://github.com/sapientpro/image-comparator

Compare images using PHP
https://github.com/sapientpro/image-comparator

image-comparison image-hashing php php-library php8

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Compare images using PHP

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# Image Comparator: Compare images using PHP



![https://packagist.org/packages/sapientpro/image-comparator](https://img.shields.io/packagist/dt/sapientpro/image-comparator)

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* [Image Comparator: Compare images using PHP](#image-comparator-compare-images-using-php)

  * [Installation](#installation)

    * [Prerequisites](#prerequisites)

  * [Usage](#usage)

  * [Available methods](#available-methods)



Image Comparator is a PHP library for image comparison and hashing.

You can compare 2 and more images using perceptual hashing method.



Based on https://github.com/kennethrapp/phasher package, with PHP 8 and PHPUnit support.

The original project was abandoned in November 2017.



Perceptual hashing is a method to generate a hash of an image which allows multiple images to be compared by an index of similarity.

You can find out more at [The Hacker Factor](http://www.hackerfactor.com/blog/index.php?/archives/432-Looks-Like-It.html)

and [phash.org](http://phash.org).



## Installation



### Prerequisites



* PHP 8.1 or higher

* gd extension enabled



To install the library, run:



`composer require sapientpro/image-comparator`



## Usage



`ImageComparator` is the core class of the library:



```php

use SapientPro\ImageComparator\ImageComparator;



$imageComparator = new ImageComparator()

```



After creating an instance you can use one of the methods available:



```php

$imageComparator->compare('your-images/your-image1.jpg', 'your-images/your-image12.jpg');

```



If the image path can't be resolved, `ImageResourceException` will be thrown:



```php

$imageComparator->hashImage('your-images/non-existent-image.jpg'); // SapientPro\ImageComparator\ImageResourceException: Could not create an image resource from file

```



Example usage:



We have two images:



https://github.com/sapientpro/image-comparator/blob/master/tests/images/ebay-image.png?raw=true



![Equals1](https://github.com/sapientpro/image-comparator/blob/master/tests/images/ebay-image.png?raw=true)

![Equals2](https://github.com/sapientpro/image-comparator/blob/master/tests/images/amazon-image.png?raw=true)



Now, let's compare them:



```php

use SapientPro\ImageComparator\ImageComparator;



$image1 = 'https://github.com/sapientpro/image-comparator/blob/feature/phasher-implementation/tests/images/ebay-image.png?raw=true';

$image2 = 'https://github.com/sapientpro/image-comparator/blob/feature/phasher-implementation/tests/images/amazon-image.png?raw=true'



$imageComparator = new ImageComparator();

$similarity = $imageComparator->compare($image1, $image2); //default hashing without rotation



echo $similarity; //87.5

```

The higher the result, the higher the similarity of images.



Let's compare different images:



![Equals1](https://github.com/sapientpro/image-comparator/blob/master/tests/images/ebay-image2.png?raw=true)

![Equals2](https://github.com/sapientpro/image-comparator/blob/master/tests/images/amazon-image2.png?raw=true)



```php

use SapientPro\ImageComparator\ImageComparator;



$image1 = 'https://github.com/sapientpro/image-comparator/blob/feature/phasher-implementation/tests/images/ebay-image2.png?raw=true';

$image2 = 'https://github.com/sapientpro/image-comparator/blob/feature/phasher-implementation/tests/images/amazon-image2.png?raw=true'



$imageComparator = new ImageComparator();

$similarity = $imageComparator->compare($image1, $image2); //default hashing without rotation



echo $similarity; //54.7

```



Rotation angle can be passed if compared image is rotated.

You must pass \SapientPro\ImageComparator\Enum\ImageRotationAngle enum with one of the following values:

`D0` = 0 degress, `D90` = 90 degrees, `D180` = 180 degrees, `D270` = 270 degrees



```php

use SapientPro\ImageComparator\Enum\ImageRotationAngle;



$similarity = $imageComparator->compare($image1, $image2, ImageRotationAngle::D180); //compared image will be considered rotated by 180 degrees



echo $similarity; //95.3

```



You can also use `detect()` method which will rotate the compared image and return the highest percentage of similarity:



```php

use SapientPro\ImageComparator\ImageComparator;



$image1 = 'https://raw.githubusercontent.com/sapientpro/phasher/feature/phasher-implementation/tests/images/forest1.jpg';

$image2 = 'https://raw.githubusercontent.com/sapientpro/phasher/feature/phasher-implementation/tests/images/forest1-copyrighted.jpg'



$imageComparator = new ImageComparator();

$similarity = $imageComparator->detect($image1, $image2);



echo $similarity; //95.3

```



With `compareArray()` and `detectArray()` methods you can compare the source image to any number of images you want.

The behaviour is the same as in `compare()` and `detect()` methods.



```php

use SapientPro\ImageComparator\ImageComparator;



$image1 = 'https://raw.githubusercontent.com/sapientpro/phasher/feature/phasher-implementation/tests/images/forest1.jpg';

$image2 = 'https://raw.githubusercontent.com/sapientpro/phasher/feature/phasher-implementation/tests/images/forest1-copyrighted.jpg'

$image3 = 'https://raw.githubusercontent.com/sapientpro/phasher/feature/phasher-implementation/tests/images/forest.jpg'



$imageComparator = new ImageComparator();

$similarity = $imageComparator->compareArray(

    $image1,

    [

        'forest' => $image2,

        'anotherForest' => $image3

    ]

); // returns ['forest' => 95.33, 'anotherForest' => 75.22]

```



If needed, you can create a square image resource from another image

and pass it to `compare()`, `compareArray()`, `detect()`, `detectArray` and `hashImage()` methods:



```php

use SapientPro\ImageComparator\ImageComparator;



$image1 = 'https://raw.githubusercontent.com/sapientpro/phasher/feature/phasher-implementation/tests/images/forest1.jpg';

$image2 = 'https://raw.githubusercontent.com/sapientpro/phasher/feature/phasher-implementation/tests/images/forest1-copyrighted.jpg'



$imageComparator = new ImageComparator();



$squareImage1 = $imageComparator->squareImage($image1);

$squareImage2 = $imageComparator->squareImage($image2);



$similarity = $imageComparator->compare($squareImage1, $squareImage2);



echo $similarity //96.43;

```



If needed, you can convert the resulting array from `hashImage()` to a binary string and pass it to `compareHashStrings()` method:



```php

use SapientPro\ImageComparator\ImageComparator;



$image1 = 'https://raw.githubusercontent.com/sapientpro/phasher/feature/phasher-implementation/tests/images/forest1.jpg';

$image2 = 'https://raw.githubusercontent.com/sapientpro/phasher/feature/phasher-implementation/tests/images/forest1-copyrighted.jpg'



$imageComparator = new ImageComparator();



$hash1 = $imageComparator->hashImage($image1);

$hash2 = $imageComparator->hashImage($image2);



$hashString1 = $imageComparator->convertHashToBinaryString($hash1);

$hashString2 = $imageComparator->convertHashToBinaryString($hash2);



$similarity = $imageComparator->compareHashStrings($hashString1, $hashString2);



echo $similarity //96.43;

```



By default, images are hashed using the average hashing algorithm,

which is implemented in `SapientPro\ImageComparator\Strategy\AverageHashStrategy`.

This strategy is initialized in the constructor of `ImageComparator`.



It is also possible to use difference hashing algorithm, implemented in SapientPro\ImageComparator\Strategy\DifferenceHashStrategy.

To use it, you need to call ImageComparator's `setHashStrategy()` method and pass the instance of the strategy:



```php

use SapientPro\ImageComparator\Strategy\DifferenceHashStrategy;



$imageComparator->setHashStrategy(new DifferenceHashStrategy());

$imageComparator->hashImage('image1.jpg');

```



If the strategy is set by `setHashingStrategy()`, it will be used under the hood in other comparison methods:



```php

use SapientPro\ImageComparator\Strategy\DifferenceHashStrategy;



$imageComparator->setHashStrategy(new DifferenceHashStrategy());

$imageComparator->compare('image1.jpg', 'image2.jpg'); // images will be hashed using difference hash algorithm and then compared

```



## Available methods



You can read about available methods in our [wiki page](https://github.com/sapientpro/image-comparator/wiki)