From d45fe53b3f94551ccdefdac6a5d53f4cf4245fca Mon Sep 17 00:00:00 2001
From: tijmen <tijmenbruggeman@gmail.com>
Date: Thu, 17 Sep 2026 09:15:50 +0200
Subject: [PATCH] ensure conversion sizes are consistent

---
 src/class-tiny-image.php    | 20 ++++-----
 test/unit/TinyImageTest.php | 87 +++++++++++++++++++++++++++++++++++++
 2 files changed, 97 insertions(+), 10 deletions(-)

diff --git a/src/class-tiny-image.php b/src/class-tiny-image.php
index 60fac156..1306fa66 100644
--- a/src/class-tiny-image.php
+++ b/src/class-tiny-image.php
@@ -621,7 +621,8 @@ public function can_be_converted() {
 
 	/**
 	 * Get the targeted conversion.
-	 * If original is already converted, then we use the originals' mimetype.
+	 * If a size is already converted, then we use that size's mimetype so
+	 * sizes never mix formats, even when the settings changed since.
 	 * If nothing is converted yet, we use the settings conversion settings.
 	 *
 	 * @since 3.6.4
@@ -635,15 +636,14 @@ private function convert_to() {
 			return array();
 		}
 
-		if ( isset( $this->sizes[ self::ORIGINAL ] ) ) {
-			// original is not in sizes so mimetypes are open
-			return $convert_settings['convert_to'];
-		}
-
-		$original_img_size = $this->sizes[ self::ORIGINAL ];
-		if ( $original_img_size->converted() ) {
-			// original has been convert so use that mimetype to convert to
-			return array( $original_img_size->meta['convert']['type'] );
+		foreach ( $this->sizes as $size ) {
+			if ( ! $size->converted() ) {
+				continue;
+			}
+			$type = $size->meta['convert']['type'];
+			if ( in_array( $type, array( 'image/avif', 'image/webp' ), true ) ) {
+				return array( $type );
+			}
 		}
 
 		return $convert_settings['convert_to'];
diff --git a/test/unit/TinyImageTest.php b/test/unit/TinyImageTest.php
index df4072b3..bbffeed2 100644
--- a/test/unit/TinyImageTest.php
+++ b/test/unit/TinyImageTest.php
@@ -1,5 +1,7 @@
 <?php
 
+use function PHPUnit\Framework\assertEquals;
+
 require_once dirname( __FILE__ ) . '/TinyTestCase.php';
 
 class Tiny_Image_Test extends Tiny_TestCase {
@@ -367,4 +369,89 @@ public function test_conversion_same_mimetype()
 		$this->assertEquals(array('image/webp'), $compress_calls[1]['convert_to']);
 	}
 
+	/**
+	 * A size added after the original was converted gets the original's format.
+	 */
+	public function test_later_compression_converts_to_format_of_earlier_conversion()
+	{
+		$this->wp->addOption('tinypng_convert_format', array(
+			'convert' => 'on',
+			'convert_to' => 'smallest',
+		));
+		$this->wp->addOption('tinypng_sizes', array(
+			Tiny_Image::ORIGINAL => 'on',
+			'thumbnail' => 'on',
+		));
+		$this->wp->stub('get_post_mime_type', function () {
+			return 'image/png';
+		});
+		$this->wp->createImages(array());
+
+		$settings = new Tiny_Settings();
+		$mock_compressor = $this->createMock(Tiny_Compress::class);
+		$convert_to_calls = array();
+		$mock_compressor->method('compress_file')
+			->willReturnCallback(function ($file, $resize, $preserve, $convert_to) use (&$convert_to_calls) {
+				$convert_to_calls[] = $convert_to;
+				return array(
+					'input' => array('size' => 12345),
+					'output' => array('size' => 12345, 'type' => 'image/png'),
+					'convert' => array('type' => 'image/avif', 'size' => 9000, 'path' => 'vfs://root/test.avif'),
+				);
+			});
+		$settings->set_compressor($mock_compressor);
+
+		// first run: only the original exists
+		$tinyimg = new Tiny_Image($settings, 999, $this->wp->getTestMetadata());
+		$tinyimg->compress();
+
+		// second run: a thumbnail has been added since
+		$this->wp->createImage(1000, '14/01', 'test-thumbnail.png');
+		$tinyimg = new Tiny_Image($settings, 999, $this->wp->getTestMetadata());
+		$tinyimg->compress();
+
+
+		assertEquals(array('image/avif', 'image/webp'), $convert_to_calls[0], 'original can be converted to avif and webp');
+		assertEquals(array('image/avif'), $convert_to_calls[1], 'original output was avif so expect subsequent sizes to avif');
+	}
+
+	/**
+	 * Marking as compressed records the original's own mimetype as conversion,
+	 * a size added afterwards must not be converted to that mimetype.
+	 */
+	public function test_compression_after_mark_as_compressed_uses_conversion_settings()
+	{
+		$this->wp->addOption('tinypng_convert_format', array(
+			'convert' => 'on',
+			'convert_to' => 'smallest',
+		));
+		$this->wp->addOption('tinypng_sizes', array(
+			Tiny_Image::ORIGINAL => 'on',
+			'thumbnail' => 'on',
+		));
+		$this->wp->stub('get_post_mime_type', function () {
+			return 'image/png';
+		});
+		$this->wp->createImages(array());
+
+		$settings = new Tiny_Settings();
+		$tinyimg = new Tiny_Image($settings, 999, $this->wp->getTestMetadata());
+		$tinyimg->mark_as_compressed();
+
+		$mock_compressor = $this->createMock(Tiny_Compress::class);
+
+		// assert that 
+		$mock_compressor->expects($this->once())
+			->method('compress_file')
+			->with($this->anything(), $this->anything(), $this->anything(), array('image/avif', 'image/webp'))
+			->willReturn(array(
+				'input' => array('size' => 1000),
+				'output' => array('size' => 1000, 'type' => 'image/png'),
+			));
+		$settings->set_compressor($mock_compressor);
+
+		$this->wp->createImage(1000, '14/01', 'test-thumbnail.png');
+		$tinyimg = new Tiny_Image($settings, 999, $this->wp->getTestMetadata());
+		$tinyimg->compress();
+	}
 }