diff --git a/src/Geometry/Resizer.php b/src/Geometry/Resizer.php
new file mode 100644
index 00000000..d804194c
--- /dev/null
+++ b/src/Geometry/Resizer.php
@@ -0,0 +1,194 @@
+<?php
+
+namespace Intervention\Image\Geometry;
+
+use Intervention\Image\Interfaces\SizeInterface;
+
+class Resizer
+{
+    /**
+     * Size to be resized
+     *
+     * @var SizeInterface
+     */
+    protected $size;
+
+    /**
+     * Target size
+     *
+     * @var SizeInterface
+     */
+    protected $target;
+
+    public function __construct(SizeInterface $size)
+    {
+        $this->size = $size;
+        $this->target = new Size(0, 0);
+    }
+
+    public static function fromSize(SizeInterface $size): self
+    {
+        return new self($size);
+    }
+
+    public function getSize(): SizeInterface
+    {
+        return $this->size;
+    }
+
+    protected function hasTargetWidth(): bool
+    {
+        return $this->target->getWidth() > 0;
+    }
+
+    protected function hasTargetHeight(): bool
+    {
+        return $this->target->getHeight() > 0;
+    }
+
+    public function width(int $width): self
+    {
+        $this->target->setWidth($width);
+
+        return $this;
+    }
+
+    public function height(int $height): self
+    {
+        $this->target->setHeight($height);
+
+        return $this;
+    }
+
+    public function setTargetSizeByArray(array $arguments): self
+    {
+        if (isset($arguments[0]) && is_callable($arguments[0])) {
+            $arguments[0]($this);
+
+            return $this;
+        }
+
+        if (isset($arguments[0]) && is_numeric($arguments[0])) {
+            $this->width($arguments[0]);
+        }
+
+        if (isset($arguments[1]) && is_numeric($arguments[1])) {
+            $this->height($arguments[1]);
+        }
+
+        return $this;
+    }
+
+    public function setTargetSize(SizeInterface $size): self
+    {
+        $this->target = $size;
+
+        return $this;
+    }
+
+    public function resize(): SizeInterface
+    {
+        $resized = clone $this->size;
+
+        if ($this->hasTargetWidth()) {
+            $resized->setWidth($this->target->getWidth());
+        }
+
+        if ($this->hasTargetHeight()) {
+            $resized->setHeight($this->target->getHeight());
+        }
+
+        return $resized;
+    }
+
+    public function resizeDown(): SizeInterface
+    {
+        if ($this->hasTargetWidth()) {
+            $this->target->setWidth(
+                min($this->target->getWidth(), $this->size->getWidth())
+            );
+        }
+
+        if ($this->hasTargetHeight()) {
+            $this->target->setHeight(
+                min($this->target->getHeight(), $this->size->getHeight())
+            );
+        }
+
+        return $this->resize();
+    }
+
+    public function scale(): SizeInterface
+    {
+        if ($this->hasTargetWidth() && $this->hasTargetHeight()) {
+            $this->target->setWidth(min(
+                $this->getProportionalWidth(),
+                $this->target->getWidth()
+            ));
+            $this->target->setHeight(min(
+                $this->getProportionalHeight(),
+                $this->target->getHeight()
+            ));
+        } elseif ($this->hasTargetWidth()) {
+            $this->target->setHeight($this->getProportionalHeight());
+        } elseif ($this->hasTargetHeight()) {
+            $this->target->setWidth($this->getProportionalWidth());
+        }
+
+        return $this->resize();
+    }
+
+    public function scaleDown(): SizeInterface
+    {
+        if ($this->hasTargetWidth() && $this->hasTargetHeight()) {
+            $this->target->setWidth(min(
+                $this->getProportionalWidth(),
+                $this->target->getWidth(),
+                $this->size->getWidth()
+            ));
+            $this->target->setHeight(min(
+                $this->getProportionalHeight(),
+                $this->target->getHeight(),
+                $this->size->getHeight()
+            ));
+        } elseif ($this->hasTargetWidth()) {
+            $this->target->setWidth(min(
+                $this->target->getWidth(),
+                $this->size->getWidth()
+            ));
+            $this->target->setHeight(min(
+                $this->getProportionalHeight(),
+                $this->size->getHeight()
+            ));
+        } elseif ($this->hasTargetHeight()) {
+            $this->target->setWidth(min(
+                $this->getProportionalWidth(),
+                $this->size->getWidth()
+            ));
+            $this->target->setHeight(min(
+                $this->target->getHeight(),
+                $this->size->getHeight()
+            ));
+        }
+
+        return $this->resize();
+    }
+
+    protected function getProportionalWidth(): int
+    {
+        if (! $this->hasTargetHeight()) {
+            return $this->size->getWidth();
+        }
+
+        return (int) round($this->target->getHeight() * $this->size->getAspectRatio());
+    }
+
+    protected function getProportionalHeight(): int
+    {
+        if (! $this->hasTargetWidth()) {
+            return $this->size->getHeight();
+        }
+
+        return (int) round($this->target->getWidth() / $this->size->getAspectRatio());
+    }
+}
diff --git a/tests/Geometry/ResizerTest.php b/tests/Geometry/ResizerTest.php
new file mode 100644
index 00000000..5395aaff
--- /dev/null
+++ b/tests/Geometry/ResizerTest.php
@@ -0,0 +1,370 @@
+<?php
+
+namespace Intervention\Image\Tests\Geometry;
+
+use Intervention\Image\Geometry\Resizer;
+use Intervention\Image\Geometry\Size;
+use PHPUnit\Framework\TestCase;
+
+class ResizerTest extends TestCase
+{
+    public function testSetTargetSizeByArray()
+    {
+        $resizer = new Resizer(new Size(300, 200));
+        $result = $resizer->setTargetSizeByArray([800, 600]);
+        $this->assertInstanceOf(Resizer::class, $result);
+        $this->assertEquals(800, $result->resize()->getWidth());
+        $this->assertEquals(600, $result->resize()->getHeight());
+
+        $resizer = new Resizer(new Size(300, 200));
+        $result = $resizer->setTargetSizeByArray([800]);
+        $this->assertInstanceOf(Resizer::class, $result);
+        $this->assertEquals(800, $result->resize()->getWidth());
+        $this->assertEquals(200, $result->resize()->getHeight());
+
+        $resizer = new Resizer(new Size(300, 200));
+        $result = $resizer->setTargetSizeByArray([function ($size) {
+            $size->width(80);
+            $size->height(40);
+        }]);
+        $this->assertInstanceOf(Resizer::class, $result);
+        $this->assertEquals(80, $result->resize()->getWidth());
+        $this->assertEquals(40, $result->resize()->getHeight());
+
+        $resizer = new Resizer(new Size(300, 200));
+        $result = $resizer->setTargetSizeByArray([function ($size) {
+            $size->width(80);
+        }]);
+        $this->assertInstanceOf(Resizer::class, $result);
+        $this->assertEquals(80, $result->resize()->getWidth());
+        $this->assertEquals(200, $result->resize()->getHeight());
+
+        $resizer = new Resizer(new Size(300, 200));
+        $result = $resizer->setTargetSizeByArray([function ($size) {
+            $size->height(10);
+        }]);
+        $this->assertInstanceOf(Resizer::class, $result);
+        $this->assertEquals(300, $result->resize()->getWidth());
+        $this->assertEquals(10, $result->resize()->getHeight());
+    }
+
+    public function testSetTargetSize(): void
+    {
+        $resizer = new Resizer(new Size(300, 200));
+        $result = $resizer->setTargetSize(new Size(200, 100));
+        $this->assertInstanceOf(Resizer::class, $result);
+        $this->assertEquals(200, $result->resize()->getWidth());
+        $this->assertEquals(100, $result->resize()->getHeight());
+    }
+
+    public function testResize()
+    {
+        $size = new Size(300, 200);
+        $resizer = new Resizer($size);
+        $resizer->width(150);
+        $result = $resizer->resize();
+        $original = $resizer->getSize();
+        $this->assertEquals(150, $result->getWidth());
+        $this->assertEquals(200, $result->getHeight());
+        $this->assertEquals(300, $original->getWidth());
+        $this->assertEquals(200, $original->getHeight());
+
+        $size = new Size(300, 200);
+        $resizer = new Resizer($size);
+        $resizer->width(20);
+        $resizer->height(10);
+        $result = $resizer->resize();
+        $original = $resizer->getSize();
+        $this->assertEquals(20, $result->getWidth());
+        $this->assertEquals(10, $result->getHeight());
+        $this->assertEquals(300, $original->getWidth());
+        $this->assertEquals(200, $original->getHeight());
+    }
+
+    public function testResizeDown()
+    {
+        // 800x600 > 1000x2000 = 800x600
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(1000);
+        $resizer->height(2000);
+        $result = $resizer->resizeDown();
+        $this->assertEquals(800, $result->getWidth());
+        $this->assertEquals(600, $result->getHeight());
+
+        // 800x600 > 400x1000 = 400x600
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(400);
+        $resizer->height(1000);
+        $result = $resizer->resizeDown();
+        $this->assertEquals(400, $result->getWidth());
+        $this->assertEquals(600, $result->getHeight());
+
+        // 800x600 > 1000x400 = 800x400
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(1000);
+        $resizer->height(400);
+        $result = $resizer->resizeDown();
+        $this->assertEquals(800, $result->getWidth());
+        $this->assertEquals(400, $result->getHeight());
+
+        // 800x600 > 400x300 = 400x300
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(400);
+        $resizer->height(300);
+        $result = $resizer->resizeDown();
+        $this->assertEquals(400, $result->getWidth());
+        $this->assertEquals(300, $result->getHeight());
+
+        // 800x600 > 1000xnull = 800x600
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(1000);
+        $result = $resizer->resizeDown();
+        $this->assertEquals(800, $result->getWidth());
+        $this->assertEquals(600, $result->getHeight());
+
+        // 800x600 > nullx1000 = 800x600
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->height(1000);
+        $result = $resizer->resizeDown();
+        $this->assertEquals(800, $result->getWidth());
+        $this->assertEquals(600, $result->getHeight());
+    }
+
+    public function testScale()
+    {
+        // 800x600 > 1000x2000 = 1000x750
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(1000);
+        $resizer->height(2000);
+        $result = $resizer->scale();
+        $this->assertEquals(1000, $result->getWidth());
+        $this->assertEquals(750, $result->getHeight());
+
+        // 800x600 > 2000x1000 = 1333x1000
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(2000);
+        $resizer->height(1000);
+        $result = $resizer->scale();
+        $this->assertEquals(1333, $result->getWidth());
+        $this->assertEquals(1000, $result->getHeight());
+
+        // // 800x600 > nullx3000 = 4000x3000
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->height(3000);
+        $result = $resizer->scale();
+        $this->assertEquals(4000, $result->getWidth());
+        $this->assertEquals(3000, $result->getHeight());
+
+        // // 800x600 > 8000xnull = 8000x6000
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(8000);
+        $result = $resizer->scale();
+        $this->assertEquals(8000, $result->getWidth());
+        $this->assertEquals(6000, $result->getHeight());
+
+        // // 800x600 > 100x400 = 100x75
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(100);
+        $resizer->height(400);
+        $result = $resizer->scale();
+        $this->assertEquals(100, $result->getWidth());
+        $this->assertEquals(75, $result->getHeight());
+
+        // // 800x600 > 400x100 = 133x100
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(400);
+        $resizer->height(100);
+        $result = $resizer->scale();
+        $this->assertEquals(133, $result->getWidth());
+        $this->assertEquals(100, $result->getHeight());
+
+        // // 800x600 > nullx300 = 400x300
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->height(300);
+        $result = $resizer->scale();
+        $this->assertEquals(400, $result->getWidth());
+        $this->assertEquals(300, $result->getHeight());
+
+        // // 800x600 > 80xnull = 80x60
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(80);
+        $result = $resizer->scale();
+        $this->assertEquals(80, $result->getWidth());
+        $this->assertEquals(60, $result->getHeight());
+
+        // // 640x480 > 225xnull = 225x169
+        $size = new Size(640, 480);
+        $resizer = new Resizer($size);
+        $resizer->width(225);
+        $result = $resizer->scale();
+        $this->assertEquals(225, $result->getWidth());
+        $this->assertEquals(169, $result->getHeight());
+
+        // // 640x480 > 223xnull = 223x167
+        $size = new Size(640, 480);
+        $resizer = new Resizer($size);
+        $resizer->width(223);
+        $result = $resizer->scale();
+        $this->assertEquals(223, $result->getWidth());
+        $this->assertEquals(167, $result->getHeight());
+
+        // // 600x800 > 300x300 = 225x300
+        $size = new Size(600, 800);
+        $resizer = new Resizer($size);
+        $resizer->width(300);
+        $resizer->height(300);
+        $result = $resizer->scale();
+        $this->assertEquals(225, $result->getWidth());
+        $this->assertEquals(300, $result->getHeight());
+
+        // // 800x600 > 400x10 = 13x10
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(400);
+        $resizer->height(10);
+        $result = $resizer->scale();
+        $this->assertEquals(13, $result->getWidth());
+        $this->assertEquals(10, $result->getHeight());
+
+        // // 800x600 > 1000x1200 = 1000x750
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(1000);
+        $resizer->height(1200);
+        $result = $resizer->scale();
+        $this->assertEquals(1000, $result->getWidth());
+        $this->assertEquals(750, $result->getHeight());
+
+        $size = new Size(12000, 12);
+        $resizer = new Resizer($size);
+        $resizer->width(4000);
+        $resizer->height(3000);
+        $result = $resizer->scale();
+        $this->assertEquals(4000, $result->getWidth());
+        $this->assertEquals(4, $result->getHeight());
+
+        $size = new Size(12, 12000);
+        $resizer = new Resizer($size);
+        $resizer->width(4000);
+        $resizer->height(3000);
+        $result = $resizer->scale();
+        $this->assertEquals(3, $result->getWidth());
+        $this->assertEquals(3000, $result->getHeight());
+
+        $size = new Size(12000, 6000);
+        $resizer = new Resizer($size);
+        $resizer->width(4000);
+        $resizer->height(3000);
+        $result = $resizer->scale();
+        $this->assertEquals(4000, $result->getWidth());
+        $this->assertEquals(2000, $result->getHeight());
+    }
+
+    public function testScaleDown()
+    {
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(1000);
+        $resizer->height(2000);
+        $result = $resizer->scaleDown();
+        $this->assertEquals(800, $result->getWidth());
+        $this->assertEquals(600, $result->getHeight());
+
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(1000);
+        $resizer->height(600);
+        $result = $resizer->scaleDown();
+        $this->assertEquals(800, $result->getWidth());
+        $this->assertEquals(600, $result->getHeight());
+
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(1000);
+        $resizer->height(300);
+        $result = $resizer->scaleDown();
+        $this->assertEquals(400, $result->getWidth());
+        $this->assertEquals(300, $result->getHeight());
+
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(400);
+        $resizer->height(1000);
+        $result = $resizer->scaleDown();
+        $this->assertEquals(400, $result->getWidth());
+        $this->assertEquals(300, $result->getHeight());
+
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(400);
+        $result = $resizer->scaleDown();
+        $this->assertEquals(400, $result->getWidth());
+        $this->assertEquals(300, $result->getHeight());
+
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->height(300);
+        $result = $resizer->scaleDown();
+        $this->assertEquals(400, $result->getWidth());
+        $this->assertEquals(300, $result->getHeight());
+
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(1000);
+        $result = $resizer->scaleDown();
+        $this->assertEquals(800, $result->getWidth());
+        $this->assertEquals(600, $result->getHeight());
+
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->height(1000);
+        $result = $resizer->scaleDown();
+        $this->assertEquals(800, $result->getWidth());
+        $this->assertEquals(600, $result->getHeight());
+
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(100);
+        $result = $resizer->scaleDown();
+        $this->assertEquals(100, $result->getWidth());
+        $this->assertEquals(75, $result->getHeight());
+
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(300);
+        $resizer->height(200);
+        $result = $resizer->scaleDown();
+        $this->assertEquals(267, $result->getWidth());
+        $this->assertEquals(200, $result->getHeight());
+
+        $size = new Size(600, 800);
+        $resizer = new Resizer($size);
+        $resizer->width(300);
+        $resizer->height(300);
+        $result = $resizer->scaleDown();
+        $this->assertEquals(225, $result->getWidth());
+        $this->assertEquals(300, $result->getHeight());
+
+        $size = new Size(800, 600);
+        $resizer = new Resizer($size);
+        $resizer->width(400);
+        $resizer->height(10);
+        $result = $resizer->scaleDown();
+        $this->assertEquals(13, $result->getWidth());
+        $this->assertEquals(10, $result->getHeight());
+    }
+}