Add sharpen method.

src/Drivers/Gd/GdDriver.php

@@ -373,4 +373,23 @@ public function sepia(): ImageDriver
             ->colorize(38, 25, 10)
             ->contrast(5);
     }
+
+    public function sharpen(float $amount): self
+    {
+        $this->ensureNumberBetween($amount, 0, 100, 'sharpen');
+
+        $min = $amount >= 10 ? $amount * -0.01 : 0;
+        $max = $amount * -0.025;
+        $abs = ((4 * $min + 4 * $max) * -1) + 1;
+
+        $matrix = [
+            [$min, $max, $min],
+            [$max, $abs, $max],
+            [$min, $max, $min]
+        ];
+
+        imageconvolution($this->image, $matrix, 1, 0);
+
+        return $this;
+    }
 }

src/Drivers/ImageDriver.php

@@ -42,6 +42,8 @@ public function greyscale(): self;
 
     public function sepia(): self;
 
+    public function sharpen(float $amount): self;
+
     public function getSize(): Size;
 
     public function fit(Fit $fit, int $desiredWidth = null, int $desiredHeight = null): self;

src/Drivers/Imagick/ImagickDriver.php

@@ -299,4 +299,13 @@ public function sepia(): ImageDriver
             ->brightness(-10)
             ->contrast(10);
     }
+
+    public function sharpen(float $amount): self
+    {
+        $this->ensureNumberBetween($amount, 0, 100, 'sharpen');
+
+        $this->image->unsharpMaskImage(1, 1, $amount / 6.25, 0);
+
+        return $this;
+    }
 }

tests/Manipulations/SharpenTest.php

@@ -0,0 +1,16 @@
+<?php
+
+use Spatie\Image\Drivers\ImageDriver;
+use Spatie\Image\Exceptions\InvalidManipulation;
+
+it('can sharpen an image', function (ImageDriver $driver) {
+    $targetFile = $this->tempDir->path("{$driver->driverName()}/sharpen.jpg");
+
+    $driver->load(getTestJpg())->sharpen(50)->save($targetFile);
+
+    expect($targetFile)->toBeFile();
+})->with('drivers');
+
+it('will throw an exception when passing an invalid sharpen value', function (ImageDriver $driver) {
+    $driver->load(getTestJpg())->sharpen(101);
+})->with('drivers')->throws(InvalidManipulation::class);