From 7350b6047d23be154d308ee82a61213c47e749dc Mon Sep 17 00:00:00 2001
From: klementyev <klermonte@yandex.ru>
Date: Thu, 20 Apr 2017 21:01:27 +0300
Subject: [PATCH 1/3] Fix hexadecimal to decimal conversion for negative 
 hashes

---
 src/ImageHash.php       | 19 +++++++++++++++++--
 tests/ImageHashTest.php | 10 ++++++++++
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/src/ImageHash.php b/src/ImageHash.php
index 55ea5f8..fcd6799 100644
--- a/src/ImageHash.php
+++ b/src/ImageHash.php
@@ -113,8 +113,8 @@ public function distance($hash1, $hash2)
             }
         } else {
             if ($this->mode === self::HEXADECIMAL) {
-                $hash1 = hexdec($hash1);
-                $hash2 = hexdec($hash2);
+                $hash1 = $this->hexdec($hash1);
+                $hash2 = $this->hexdec($hash2);
             }
 
             $dh = 0;
@@ -179,4 +179,19 @@ protected function formatHash($hash)
     {
         return $this->mode === static::HEXADECIMAL ? dechex($hash) : $hash;
     }
+
+    /**
+     * Convert hexadecimal to signed decimal.
+     *
+     * @param string $hex
+     * @return int
+     */
+    protected function hexdec($hex)
+    {
+        if (strlen($hex) == 16 && hexdec($hex[0]) > 8) {
+            return unpack('J', hex2bin($hex))[1];
+        }
+
+        return hexdec($hex);
+    }
 }
diff --git a/tests/ImageHashTest.php b/tests/ImageHashTest.php
index 140eee6..ffefecb 100644
--- a/tests/ImageHashTest.php
+++ b/tests/ImageHashTest.php
@@ -31,4 +31,14 @@ public function testHashStringSameAsFile()
 
         $this->assertSame($this->imageHash->hash($path), $this->imageHash->hashFromString(file_get_contents($path)));
     }
+
+    public function testDistanceOfNegativeHashes()
+    {
+        $imageHash = new ImageHash(null, ImageHash::HEXADECIMAL);
+        $hash1 = 'ffffffffffffffff'; // -1
+        $hash2 = 'fffffffffffffff0'; // -16
+
+        $distance = $imageHash->distance($hash1, $hash2);
+        $this->assertEquals(4, $distance);
+    }
 }

From b6d7b81f335b68dee37831788d6a42e3cadb3779 Mon Sep 17 00:00:00 2001
From: klementyev <klermonte@yandex.ru>
Date: Thu, 20 Apr 2017 21:51:35 +0300
Subject: [PATCH 2/3] add test

---
 src/ImageHash.php       | 30 +++++++++++++++---------------
 tests/ImageHashTest.php | 12 ++++++++++++
 2 files changed, 27 insertions(+), 15 deletions(-)

diff --git a/src/ImageHash.php b/src/ImageHash.php
index fcd6799..849c1a5 100644
--- a/src/ImageHash.php
+++ b/src/ImageHash.php
@@ -129,6 +129,21 @@ public function distance($hash1, $hash2)
         return $dh;
     }
 
+    /**
+     * Convert hexadecimal to signed decimal.
+     *
+     * @param string $hex
+     * @return int
+     */
+    public function hexdec($hex)
+    {
+        if (strlen($hex) == 16 && hexdec($hex[0]) > 8) {
+            return unpack('J', hex2bin($hex))[1];
+        }
+
+        return hexdec($hex);
+    }
+
     /**
      * Get a GD2 resource from file.
      *
@@ -179,19 +194,4 @@ protected function formatHash($hash)
     {
         return $this->mode === static::HEXADECIMAL ? dechex($hash) : $hash;
     }
-
-    /**
-     * Convert hexadecimal to signed decimal.
-     *
-     * @param string $hex
-     * @return int
-     */
-    protected function hexdec($hex)
-    {
-        if (strlen($hex) == 16 && hexdec($hex[0]) > 8) {
-            return unpack('J', hex2bin($hex))[1];
-        }
-
-        return hexdec($hex);
-    }
 }
diff --git a/tests/ImageHashTest.php b/tests/ImageHashTest.php
index ffefecb..784f8ae 100644
--- a/tests/ImageHashTest.php
+++ b/tests/ImageHashTest.php
@@ -32,6 +32,18 @@ public function testHashStringSameAsFile()
         $this->assertSame($this->imageHash->hash($path), $this->imageHash->hashFromString(file_get_contents($path)));
     }
 
+    public function testHexdecForNegativeIntegers()
+    {
+        // native hexdec dechex conversion working for positive integers
+        $this->assertEquals(1, hexdec(dechex(1)));
+        // but not working for negative
+        $this->assertNotEquals(-1, hexdec(dechex(-1)));
+
+        // custom hexdec implementation works for both
+        $this->assertEquals(1, $this->imageHash->hexdec(dechex(1)));
+        $this->assertEquals(-1, $this->imageHash->hexdec(dechex(-1)));
+    }
+
     public function testDistanceOfNegativeHashes()
     {
         $imageHash = new ImageHash(null, ImageHash::HEXADECIMAL);

From 337bc08b7cb0a16b54fc81af49351b4d4728932b Mon Sep 17 00:00:00 2001
From: klementyev <klermonte@yandex.ru>
Date: Thu, 20 Apr 2017 22:07:41 +0300
Subject: [PATCH 3/3] use fallback for php <= 5.5

---
 src/ImageHash.php | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/ImageHash.php b/src/ImageHash.php
index 849c1a5..1bed620 100644
--- a/src/ImageHash.php
+++ b/src/ImageHash.php
@@ -138,7 +138,8 @@ public function distance($hash1, $hash2)
     public function hexdec($hex)
     {
         if (strlen($hex) == 16 && hexdec($hex[0]) > 8) {
-            return unpack('J', hex2bin($hex))[1];
+            list($higher, $lower) = array_values(unpack('N2', hex2bin($hex)));
+            return $higher << 32 | $lower;
         }
 
         return hexdec($hex);