Fix blur type issues, and add test for it

BlurTest.php

@@ -0,0 +1,66 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the OrbitaleImageMagickPHP package.
+ *
+ * (c) Alexandre Rock Ancelet <[email protected]>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Orbitale\Component\ImageMagick\Tests\References;
+
+use Orbitale\Component\ImageMagick\References;
+use PHPUnit\Framework\TestCase;
+
+class BlurTest extends TestCase
+{
+    /**
+     * @dataProvider provideInvalidOptions
+     */
+    public function testInvalidBlurOptions($invalidOption): void
+    {
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessage('Gaussian blur must respect formats "{radius}" or "{radius}x{sigma}".'."\n"
+            .'Please refer to ImageMagick command line documentation about the "-gaussian-blur" and "-blur" options:'."\n"
+            .'http://www.imagemagick.org/script/command-line-options.php#blur'."\n"
+            .'http://www.imagemagick.org/script/command-line-options.php#gaussian-blur');
+        $this->getReferences()->blur($invalidOption);
+    }
+
+    /**
+     * @dataProvider provideValidOptions
+     */
+    public function testValidBlurOptions($validOption, $expectedReturn): void
+    {
+        static::assertSame($expectedReturn, $this->getReferences()->blur($validOption));
+    }
+
+    public function getReferences(): References
+    {
+        return new References();
+    }
+
+    public function provideInvalidOptions(): \Generator
+    {
+        yield ['invalid'];
+        yield ['axb'];
+        yield ['   a x   b'];
+        yield ['1x2x3'];
+        yield ['1  x2'];
+        yield ['1x  2'];
+    }
+
+    public function provideValidOptions(): \Generator
+    {
+        yield [1, '1'];
+        yield [-1, '-1'];
+        yield ['1', '1'];
+        yield ['-1', '-1'];
+        yield ['1x2', '1x2'];
+        yield [' 1x2 ', '1x2'];
+    }
+}

src/Command.php

@@ -522,7 +522,7 @@ public function interlace(string $type): self
     /**
      * @see http://imagemagick.org/script/command-line-options.php#gaussian-blur
      */
-    public function gaussianBlur(string $blur): self
+    public function gaussianBlur($blur): self
     {
         $this->command[] = '-gaussian-blur';
         $this->command[] = $this->ref->blur($blur);
@@ -533,7 +533,7 @@ public function gaussianBlur(string $blur): self
     /**
      * @see http://imagemagick.org/script/command-line-options.php#blur
      */
-    public function blur(string $blur): self
+    public function blur($blur): self
     {
         $this->command[] = '-blur';
         $this->command[] = $this->ref->blur($blur);

src/References.php

@@ -185,12 +185,18 @@ public function rotation(string $rotation): string
         ));
     }
 
-    public function blur(string $blur): float
+    public function blur($blur): string
     {
-        $blur = \trim($blur);
+        if (\is_string($blur)) {
+            $blur = \trim($blur);
+        }
+
+        if (\is_numeric($blur)) {
+            return (string) (float) $blur;
+        }
 
         if (\preg_match('~^\d+(?:\.\d+)?(?:x\d+(?:\.\d+)?)?$~', $blur)) {
-            return (float) $blur;
+            return (string) $blur;
         }
 
         throw new \InvalidArgumentException(\sprintf(