Change behaviour of Image::getFrame()

Method now throws exception if the given frame could not be found.

src/Drivers/Gd/Image.php

@@ -6,6 +6,7 @@ use Intervention\Image\Collection;
 use Intervention\Image\Colors\Rgb\Colorspace as RgbColorspace;
 use Intervention\Image\Drivers\Abstract\AbstractImage;
 use Intervention\Image\Drivers\Gd\Traits\CanHandleColors;
+use Intervention\Image\Exceptions\AnimationException;
 use Intervention\Image\Exceptions\NotSupportedException;
 use Intervention\Image\Interfaces\ColorInterface;
 use Intervention\Image\Interfaces\ColorspaceInterface;
@@ -51,9 +52,13 @@ class Image extends AbstractImage implements ImageInterface, IteratorAggregate
         return $this;
     }
 
-    public function getFrame(int $position = 0): ?FrameInterface
+    public function getFrame(int $position = 0): FrameInterface
     {
-        return $this->frames->get($position);
+        if ($frame = $this->frames->get($position)) {
+            return $frame;
+        }
+
+        throw new AnimationException('Frame #' . $position . ' is not be found in the image.');
     }
 
     public function addFrame(FrameInterface $frame): ImageInterface

src/Drivers/Imagick/Image.php

@@ -12,6 +12,7 @@ use Intervention\Image\Drivers\Imagick\Modifiers\ColorspaceModifier;
 use Intervention\Image\Drivers\Imagick\Modifiers\ProfileModifier;
 use Intervention\Image\Drivers\Imagick\Modifiers\ProfileRemovalModifier;
 use Intervention\Image\Drivers\Imagick\Traits\CanHandleColors;
+use Intervention\Image\Exceptions\AnimationException;
 use Intervention\Image\Exceptions\ColorException;
 use Intervention\Image\Interfaces\ColorInterface;
 use Intervention\Image\Interfaces\ColorspaceInterface;
@@ -36,7 +37,7 @@ class Image extends AbstractImage implements ImageInterface, Iterator
         return $this->imagick;
     }
 
-    public function getFrame(int $position = 0): ?FrameInterface
+    public function getFrame(int $position = 0): FrameInterface
     {
         foreach ($this->imagick as $core) {
             if ($core->getIteratorIndex() == $position) {
@@ -44,7 +45,7 @@ class Image extends AbstractImage implements ImageInterface, Iterator
             }
         }
 
-        return null;
+        throw new AnimationException('Frame #' . $position . ' is not be found in the image.');
     }
 
     public function addFrame(FrameInterface $frame): ImageInterface

src/Exceptions/AnimationException.php

@@ -0,0 +1,8 @@
+<?php
+
+namespace Intervention\Image\Exceptions;
+
+class AnimationException extends \RuntimeException
+{
+    //
+}

src/Interfaces/ImageInterface.php

@@ -12,9 +12,9 @@ interface ImageInterface extends Traversable, Countable
      * Get frame of animation image at given position starting with zero
      *
      * @param int $position
-     * @return null|FrameInterface
+     * @return FrameInterface
      */
-    public function getFrame(int $position = 0): ?FrameInterface;
+    public function getFrame(int $position = 0): FrameInterface;
 
     /**
      * Add frame to animated image

tests/Drivers/Gd/ImageTest.php

@@ -11,6 +11,7 @@ use Intervention\Image\Colors\Rgb\Color;
 use Intervention\Image\Colors\Rgb\Colorspace as RgbColorspace;
 use Intervention\Image\Colors\Cmyk\Colorspace as CmykColorspace;
 use Intervention\Image\Exceptions\NotSupportedException;
+use Intervention\Image\Exceptions\AnimationException;
 
 /**
  * @requires extension gd
@@ -109,8 +110,8 @@ class ImageTest extends TestCase
         $this->assertInstanceOf(Color::class, $color);
         $this->assertEquals([0, 0, 255, 255], $color->toArray());
 
-        $color = $this->image->pickColor(0, 0, 3);
+        $this->expectException(AnimationException::class);
-        $this->assertNull($color);
+        $this->image->pickColor(0, 0, 3);
     }
 
     public function testPickColors(): void

tests/Drivers/Imagick/ImageTest.php

@@ -9,6 +9,7 @@ use Intervention\Image\Colors\Cmyk\Colorspace as CmykColorspace;
 use Intervention\Image\Colors\Profile;
 use Intervention\Image\Drivers\Imagick\Frame;
 use Intervention\Image\Drivers\Imagick\Image;
+use Intervention\Image\Exceptions\AnimationException;
 use Intervention\Image\Exceptions\ColorException;
 use Intervention\Image\Geometry\Rectangle;
 use Intervention\Image\Tests\TestCase;
@@ -44,12 +45,13 @@ class ImageTest extends TestCase
     {
         $this->assertInstanceOf(Image::class, $this->image);
     }
-    
+
     public function testGetFrame(): void
     {
         $this->assertInstanceOf(Frame::class, $this->image->getFrame());
         $this->assertInstanceOf(Frame::class, $this->image->getFrame(1));
-        $this->assertNull($this->image->getFrame(2));
+        $this->expectException(AnimationException::class);
+        $this->image->getFrame(2);
     }
 
     public function testAddFrame(): void