Fix WebP header generation

Author: lourot

README.md

@@ -5,6 +5,7 @@ Image metadata library (PHP 5.5+)
 > adds the following changes:
 >
 > * added `Xmp::getImageRegions()`,
+> * fixed WebP header generation,
 > * unit tests made runnable on PHP8 and newer PHPUnit,
 > * added linter to validate code against any version of PHP >= 5.5 .
 >

src/Format/WebP.php

@@ -274,7 +274,7 @@ private function getFile($chunks)
             $data .= $chunk->getChunk();
         }
 
-        $header = 'RIFF' . pack('V', strlen($chunks) + 4) . 'WEBP';
+        $header = 'RIFF' . pack('V', strlen($data) + 4) . 'WEBP';
         return $header . $data;
     }
 

tests/Format/WebPTest.php

@@ -94,6 +94,6 @@ public function testConvertsFromSimpleFormat()
         $webp = WebP::fromFile(__DIR__ . '/../Fixtures/simple.webp');
         $webp->setXmp($xmp);
 
-        var_dump($webp->getBytes());
+        // var_dump($webp->getBytes());
     }
 }