Add ResizeCanvasRelativeModifier

src/Drivers/Gd/Modifiers/ResizeCanvasRelativeModifier.php

@@ -0,0 +1,14 @@
+<?php
+
+namespace Intervention\Image\Drivers\Gd\Modifiers;
+
+use Intervention\Image\Interfaces\ImageInterface;
+use Intervention\Image\Interfaces\SizeInterface;
+
+/**
+ * @method SizeInterface cropSize(ImageInterface $image)
+ * @property mixed $background
+ */
+class ResizeCanvasRelativeModifier extends ResizeCanvasModifier
+{
+}

src/Drivers/Imagick/Modifiers/ResizeCanvasRelativeModifier.php

@@ -0,0 +1,14 @@
+<?php
+
+namespace Intervention\Image\Drivers\Imagick\Modifiers;
+
+use Intervention\Image\Interfaces\ImageInterface;
+use Intervention\Image\Interfaces\SizeInterface;
+
+/**
+ * @method SizeInterface cropSize(ImageInterface $image)
+ * @property mixed $background
+ */
+class ResizeCanvasRelativeModifier extends ResizeCanvasModifier
+{
+}

src/Image.php

@@ -65,6 +65,7 @@ use Intervention\Image\Modifiers\ProfileModifier;
 use Intervention\Image\Modifiers\ProfileRemovalModifier;
 use Intervention\Image\Modifiers\RemoveAnimationModifier;
 use Intervention\Image\Modifiers\ResizeCanvasModifier;
+use Intervention\Image\Modifiers\ResizeCanvasRelativeModifier;
 use Intervention\Image\Modifiers\ResizeDownModifier;
 use Intervention\Image\Modifiers\ResizeModifier;
 use Intervention\Image\Modifiers\ResolutionModifier;
@@ -528,14 +529,23 @@ final class Image implements ImageInterface, Countable
      * @see ImageInterface::resizeCanvas()
      */
     public function resizeCanvas(
-        int $width,
-        int $height,
+        ?int $width = null,
+        ?int $height = null,
         mixed $background = 'ffffff',
         string $position = 'center'
     ): ImageInterface {
         return $this->modify(new ResizeCanvasModifier($width, $height, $background, $position));
     }
 
+    public function resizeCanvasRelative(
+        ?int $width = null,
+        ?int $height = null,
+        mixed $background = 'ffffff',
+        string $position = 'center',
+    ): ImageInterface {
+        return $this->modify(new ResizeCanvasRelativeModifier($width, $height, $background, $position));
+    }
+
     /**
      * {@inheritdoc}
      *

src/Interfaces/ImageInterface.php

@@ -353,15 +353,33 @@ interface ImageInterface extends IteratorAggregate, Countable
      * image the resizing is going to happen. A background color can be passed
      * to define the color of the new emerging areas.
      *
-     * @param int $width
-     * @param int $height
+     * @param null|int $width
+     * @param null|int $height
      * @param string $position
      * @param mixed $background
      * @return ImageInterface
      */
     public function resizeCanvas(
-        int $width,
-        int $height,
+        ?int $width = null,
+        ?int $height = null,
+        mixed $background = 'ffffff',
+        string $position = 'center'
+    ): ImageInterface;
+
+    /**
+     * Resize canvas in the same way as resizeCanvas() but takes relative values
+     * for the width and height, which will be added or subtracted to the
+     * original image size.
+     *
+     * @param null|int $width
+     * @param null|int $height
+     * @param string $position
+     * @param mixed $background
+     * @return ImageInterface
+     */
+    public function resizeCanvasRelative(
+        ?int $width = null,
+        ?int $height = null,
         mixed $background = 'ffffff',
         string $position = 'center'
     ): ImageInterface;

src/Modifiers/ResizeCanvasModifier.php

@@ -9,8 +9,8 @@ use Intervention\Image\Interfaces\SizeInterface;
 class ResizeCanvasModifier extends AbstractModifier
 {
     public function __construct(
-        public int $width,
-        public int $height,
+        public ?int $width = null,
+        public ?int $height = null,
         public mixed $background = 'ffffff',
         public string $position = 'center'
     ) {
@@ -18,7 +18,10 @@ class ResizeCanvasModifier extends AbstractModifier
 
     public function cropSize(ImageInterface $image): SizeInterface
     {
-        return (new Rectangle($this->width, $this->height))
+        $width = is_null($this->width) ? $image->width() : $this->width;
+        $height = is_null($this->height) ? $image->height() : $this->height;
+
+        return (new Rectangle($width, $height))
             ->alignPivotTo($image->size(), $this->position);
     }
 }

src/Modifiers/ResizeCanvasRelativeModifier.php

@@ -0,0 +1,19 @@
+<?php
+
+namespace Intervention\Image\Modifiers;
+
+use Intervention\Image\Geometry\Rectangle;
+use Intervention\Image\Interfaces\ImageInterface;
+use Intervention\Image\Interfaces\SizeInterface;
+
+class ResizeCanvasRelativeModifier extends ResizeCanvasModifier
+{
+    public function cropSize(ImageInterface $image): SizeInterface
+    {
+        $width = is_null($this->width) ? $image->width() : $image->width() + $this->width;
+        $height = is_null($this->height) ? $image->height() : $image->height() + $this->height;
+
+        return (new Rectangle($width, $height))
+            ->alignPivotTo($image->size(), $this->position);
+    }
+}

tests/Drivers/Gd/Modifiers/ResizeCanvasRelativeModifierTest.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace Intervention\Image\Tests\Drivers\Gd\Modifiers;
+
+use Intervention\Image\Modifiers\ResizeCanvasRelativeModifier;
+use Intervention\Image\Tests\TestCase;
+use Intervention\Image\Tests\Traits\CanCreateGdTestImage;
+
+/**
+ * @requires extension gd
+ * @covers \Intervention\Image\Modifiers\ResizeCanvasRelativeModifier
+ */
+class ResizeCanvasRelativeModifierTest extends TestCase
+{
+    use CanCreateGdTestImage;
+
+    public function testModify(): void
+    {
+        $image = $this->createTestImage('tile.png');
+        $this->assertEquals(16, $image->width());
+        $this->assertEquals(16, $image->height());
+        $image->modify(new ResizeCanvasRelativeModifier(2, 2, 'ff0', 'center'));
+        $this->assertEquals(18, $image->width());
+        $this->assertEquals(18, $image->height());
+        $this->assertColor(255, 255, 0, 255, $image->pickColor(0, 0));
+        $this->assertColor(180, 224, 0, 255, $image->pickColor(1, 1));
+        $this->assertColor(180, 224, 0, 255, $image->pickColor(2, 2));
+        $this->assertColor(255, 255, 0, 255, $image->pickColor(17, 17));
+        $this->assertTransparency($image->pickColor(12, 1));
+    }
+}

tests/Drivers/Imagick/Modifiers/ResizeCanvasRelativeModifierTest.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace Intervention\Image\Tests\Drivers\Imagick\Modifiers;
+
+use Intervention\Image\Modifiers\ResizeCanvasRelativeModifier;
+use Intervention\Image\Tests\TestCase;
+use Intervention\Image\Tests\Traits\CanCreateImagickTestImage;
+
+/**
+ * @requires extension gd
+ * @covers \Intervention\Image\Modifiers\ResizeCanvasRelativeModifier
+ */
+class ResizeCanvasRelativeModifierTest extends TestCase
+{
+    use CanCreateImagickTestImage;
+
+    public function testModify(): void
+    {
+        $image = $this->createTestImage('tile.png');
+        $this->assertEquals(16, $image->width());
+        $this->assertEquals(16, $image->height());
+        $image->modify(new ResizeCanvasRelativeModifier(2, 2, 'ff0', 'center'));
+        $this->assertEquals(18, $image->width());
+        $this->assertEquals(18, $image->height());
+        $this->assertColor(255, 255, 0, 255, $image->pickColor(0, 0));
+        $this->assertColor(180, 224, 0, 255, $image->pickColor(1, 1));
+        $this->assertColor(180, 224, 0, 255, $image->pickColor(2, 2));
+        $this->assertColor(255, 255, 0, 255, $image->pickColor(17, 17));
+        $this->assertTransparency($image->pickColor(12, 1));
+    }
+}