Fix animated WebP crop artifacts

src/Image/Image.php

@@ -177,7 +177,7 @@ public function crop(int $width, int $height, string $gravity = Image::GRAVITY_C
         $x = intval($x);
         $y = intval($y);
 
-        if ($this->image->getImageFormat() == 'GIF') {
+        if ($this->image->getNumberImages() > 1) {
             $this->image = $this->image->coalesceImages();
 
             foreach ($this->image as $frame) {
@@ -188,18 +188,14 @@ public function crop(int $width, int $height, string $gravity = Image::GRAVITY_C
                     $frame->cropImage($width, $height, $x, $y);
                     $frame->thumbnailImage($width, $height);
                 }
-            }
 
-            $this->image->deconstructImages();
-        } else {
-            foreach ($this->image as $frame) {
-                if ($gravity === self::GRAVITY_CENTER) {
-                    $this->image->cropThumbnailImage($width, $height);
-                } else {
-                    $this->image->scaleImage($resizeWidth, $resizeHeight, false);
-                    $this->image->cropImage($width, $height, $x, $y);
-                }
+                $frame->setImagePage($width, $height, 0, 0);
             }
+        } elseif ($gravity === self::GRAVITY_CENTER) {
+            $this->image->cropThumbnailImage($width, $height);
+        } else {
+            $this->image->scaleImage($resizeWidth, $resizeHeight, false);
+            $this->image->cropImage($width, $height, $x, $y);
         }
         $this->height = $height;
         $this->width = $width;

tests/Image/ImageTest.php

@@ -859,4 +859,90 @@ public function test_gif_small_last_frame(): void
 
         \unlink($target);
     }
+
+    /**
+     * Animated WebP stores delta/partial frames. Cropping without coalesce
+     * scales those fragments independently and produces ghosting artifacts.
+     */
+    public function test_crop_animated_webp_preserves_frames(): void
+    {
+        $source = __DIR__.'/../resources/disk-a/anim-delta.webp';
+        $image = new Image(\file_get_contents($source) ?: '');
+        $target = __DIR__.'/anim-delta-32x32.webp';
+
+        $image->crop(32, 32);
+        $image->save($target, 'webp', 100);
+
+        $this->assertFileExists($target);
+        $this->assertNotEmpty(\file_get_contents($target));
+
+        $output = new \Imagick($target);
+        $this->assertGreaterThan(1, $output->getNumberImages());
+        $this->assertTrue(\in_array($output->getImageFormat(), ['PAM', 'WEBP'], true));
+
+        $coalesced = $output->coalesceImages();
+        foreach ($coalesced as $frame) {
+            $this->assertEquals(32, $frame->getImageWidth());
+            $this->assertEquals(32, $frame->getImageHeight());
+        }
+
+        // Frame 0 has a red square near the top-left; after a correct resize
+        // that region must stay red — not blended with later frames.
+        $coalesced->setFirstIterator();
+        $pixel = $coalesced->getImagePixelColor(8, 8)->getColor();
+        $this->assertGreaterThan(200, $pixel['r']);
+        $this->assertLessThan(100, $pixel['g']);
+        $this->assertLessThan(100, $pixel['b']);
+
+        // Frame 1 replaces that region with green on a correct crop.
+        $coalesced->nextImage();
+        $pixel = $coalesced->getImagePixelColor(8, 8)->getColor();
+        $this->assertLessThan(100, $pixel['r']);
+        $this->assertGreaterThan(180, $pixel['g']);
+        $this->assertLessThan(150, $pixel['b']);
+
+        \unlink($target);
+    }
+
+    /**
+     * Consecutive identical frames are hold/pause frames. Cropping must keep
+     * total playback delay — deconstructImages() + WebP encode can zero it out.
+     */
+    public function test_crop_animated_webp_preserves_hold_frames(): void
+    {
+        $sequence = new \Imagick;
+        foreach (['#ff0000', '#ff0000', '#0000ff'] as $color) {
+            $frame = new \Imagick;
+            $frame->newImage(40, 40, new \ImagickPixel($color));
+            $frame->setImageDelay(40);
+            $frame->setImageDispose(\Imagick::DISPOSE_NONE);
+            $frame->setImageFormat('gif');
+            $sequence->addImage($frame);
+        }
+
+        $blob = $sequence->getImagesBlob();
+        $this->assertNotFalse($blob);
+
+        $image = new Image($blob);
+        $image->crop(20, 20);
+        $outputBlob = $image->output('webp', 100);
+        $this->assertNotFalse($outputBlob);
+        $this->assertNotNull($outputBlob);
+
+        $output = new \Imagick;
+        $output->readImageBlob($outputBlob);
+
+        $totalDelay = 0;
+        foreach ($output as $frame) {
+            $totalDelay += $frame->getImageDelay();
+        }
+        $this->assertEquals(120, $totalDelay);
+        $this->assertGreaterThanOrEqual(2, $output->getNumberImages());
+
+        $coalesced = $output->coalesceImages();
+        foreach ($coalesced as $frame) {
+            $this->assertEquals(20, $frame->getImageWidth());
+            $this->assertEquals(20, $frame->getImageHeight());
+        }
+    }
 }