Skip images without src or srcset

src/class-tiny-picture.php

@@ -195,6 +195,10 @@ private function filter_images( $content ) {
 		}
 		$images = array();
 		foreach ( $matches[0] as $img ) {
+			// Skip images without src or srcset
+			if ( ! preg_match( '/\b(?:src|srcset)\s*=/i', $img ) ) {
+				continue;
+			}
 			$images[] = new Tiny_Source_Image(
 				$img,
 				$this->base_dir,

src/class-tiny-source-base.php

@@ -189,7 +189,10 @@ protected function create_alternative_sources( $original_source_html ) {
 		$srcsets = $this->get_image_srcsets( $original_source_html );
 		if ( empty( $srcsets ) ) {
 			// no srcset, try src attribute
-			$srcsets[] = $this->get_image_src( $original_source_html );
+			$src = $this->get_image_src( $original_source_html );
+			if ( ! empty( $src ) ) {
+				$srcsets[] = $src;
+			}
 		}
 
 		if ( empty( $srcsets ) ) {

test/unit/TinyPictureTest.php

@@ -354,4 +354,28 @@ public function test_does_not_register_hooks_when_pagebuilder_request()
 
         $_GET = array();
     }
+
+    /**
+     * images that have no src or srcset will be unchanged
+     */
+    public function test_image_without_src() {
+        $input = '<img alt="no source">';
+        $expected = '<img alt="no source">';
+        $output = $this->tiny_picture->replace_sources($input);
+
+        $this->assertSame($expected, $output);
+    }
+
+    /**
+     * Images with only a srcset are valid and will be wrapped
+     */
+    public function test_image_with_only_srcset() {
+        $this->wp->createImage(37857, '2025/09', 'test_250x250.webp');
+
+        $input = '<img srcset="/wp-content/uploads/2025/09/test_250x250.png 350w" alt="no source but has srcset">';
+        $expected = '<picture><source srcset="/wp-content/uploads/2025/09/test_250x250.webp 350w" type="image/webp" /><img srcset="/wp-content/uploads/2025/09/test_250x250.png 350w" alt="no source but has srcset"></picture>';
+        $output = $this->tiny_picture->replace_sources($input);
+
+        $this->assertSame($expected, $output);
+    }
 }