Do not write empty or duplicate metadata blocks

src/Metadata/PngContainer.php

@@ -50,10 +50,25 @@ public function apply($inputStream, $outputStream, ImageMetadata $metadata, arra
 
             if ('IDAT' === $type) {
                 fwrite($outputStream, $png);
-                fwrite($outputStream, $this->buildItxt('XML:com.adobe.xmp', $xmp));
-                fwrite($outputStream, $this->buildChunk('eXIf', $exif));
-                // Non-standard ImageMagick/exiftool/exiv2 format
-                fwrite($outputStream, $this->buildItxt('Raw profile type iptc', sprintf("\nIPTC profile\n%8d\n%s", \strlen($iptc), bin2hex($iptc))));
+
+                if ($xmp) {
+                    fwrite($outputStream, $this->buildItxt('XML:com.adobe.xmp', $xmp));
+                }
+
+                if ($exif) {
+                    fwrite($outputStream, $this->buildChunk('eXIf', $exif));
+                }
+
+                if ($iptc) {
+                    // Non-standard ImageMagick/exiftool/exiv2 format
+                    fwrite($outputStream, $this->buildItxt('Raw profile type iptc', sprintf("\nIPTC profile\n%8d\n%s", \strlen($iptc), bin2hex($iptc))));
+                }
+
+                // Copy the rest of the image
+                fwrite($outputStream, $marker);
+                stream_copy_to_stream($inputStream, $outputStream);
+
+                return;
             }
 
             fwrite($outputStream, $marker);

tests/Metadata/MetadataReaderWriterTest.php

@@ -12,7 +12,18 @@
 
 namespace Contao\Image\Tests\Metadata;
 
+use Contao\Image\Metadata\ExifFormat;
+use Contao\Image\Metadata\GifFormat;
+use Contao\Image\Metadata\ImageMetadata;
+use Contao\Image\Metadata\IptcFormat;
 use Contao\Image\Metadata\MetadataReaderWriter;
+use Contao\Image\Metadata\PngFormat;
+use Contao\Image\Metadata\XmpFormat;
+use Contao\Image\ResizeOptions;
+use Imagine\Gd\Imagine as GdImagine;
+use Imagine\Gmagick\Imagine as GmagickImagine;
+use Imagine\Image\Box;
+use Imagine\Imagick\Imagine as ImagickImagine;
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\Filesystem\Filesystem;
 
@@ -101,6 +112,53 @@ public function getParse(): \Generator
         }
     }
 
+    /**
+     * @dataProvider getFormats
+     */
+    public function testApplyDoesNotChangeForEmptyData(string $format): void
+    {
+        $supported = false;
+
+        foreach ([GdImagine::class, ImagickImagine::class, GmagickImagine::class] as $imagineClass) {
+            if (!($driverInfo = $imagineClass::getDriverInfo(false)) || !$driverInfo->isFormatSupported($format)) {
+                continue;
+            }
+
+            $supported = true;
+            $sourcePath = (new Filesystem())->tempnam(sys_get_temp_dir(), 'img');
+            $targetPath = (new Filesystem())->tempnam(sys_get_temp_dir(), 'img');
+            $imagine = new $imagineClass();
+
+            $imagine->create(new Box(100, 100))->save($sourcePath, ['format' => $format]);
+
+            (new MetadataReaderWriter())->applyCopyrightToFile(
+                $sourcePath,
+                $targetPath,
+                new ImageMetadata([
+                    XmpFormat::NAME => [],
+                    IptcFormat::NAME => [],
+                    ExifFormat::NAME => [],
+                    PngFormat::NAME => [],
+                    GifFormat::NAME => [],
+                ]),
+                (new ResizeOptions())->getPreserveCopyrightMetadata()
+            );
+
+            $this->assertFileEquals($sourcePath, $targetPath);
+
+            (new Filesystem())->remove([$sourcePath, $targetPath]);
+        }
+
+        if (!$supported) {
+            $this->markTestSkipped(sprintf('Format "%s" not supported on this system', $format));
+        }
+    }
+
+    public function getFormats(): \Generator
+    {
+        yield ['png', 'gif', 'jpg', 'webp'];
+    }
+
     private function assertExpectedArrayRecursive(array $expected, array $actual): void
     {
         foreach ($expected as $key => $value) {