From a4481bfd3315ed6cdf10f9f16aced74ced2d026b Mon Sep 17 00:00:00 2001
From: Matias Griese <matias@trilbymedia.com>
Date: Mon, 25 Jan 2021 15:25:02 +0200
Subject: [PATCH] Fixed cannot change image format [#3173]

---
 CHANGELOG.md                                            | 1 +
 system/src/Grav/Common/Media/Traits/ImageMediaTrait.php | 6 ++++--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b4572f8ba..c8088cb5f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 1. [](#bugfix)
     * Fixed `bin/gpm uninstall` script not working because of bad typehint [#3172](https://github.com/getgrav/grav/issues/3172)
     * Fixed `login: visibility_requires_access` not working [#3176](https://github.com/getgrav/grav/issues/3176)
+    * Fixed cannot change image format [#3173](https://github.com/getgrav/grav/issues/3173)
 
 # v1.7.3
 ## 01/21/2021
diff --git a/system/src/Grav/Common/Media/Traits/ImageMediaTrait.php b/system/src/Grav/Common/Media/Traits/ImageMediaTrait.php
index b187cf7a3..1acf4410c 100644
--- a/system/src/Grav/Common/Media/Traits/ImageMediaTrait.php
+++ b/system/src/Grav/Common/Media/Traits/ImageMediaTrait.php
@@ -383,8 +383,10 @@ trait ImageMediaTrait
             return $this->result;
         }
 
-        $extension = strtolower($this->get('extension'));
-        $this->format($extension);
+        if ($this->format === 'guess') {
+            $extension = strtolower($this->get('extension'));
+            $this->format($extension);
+        }
 
         if (!$this->debug_watermarked && $this->get('debug')) {
             $ratio = $this->get('ratio');