From b64faaaa261d0edc4ab33d892a19f76d4757a4fa Mon Sep 17 00:00:00 2001
From: Alx Sa <cmyk.student@gmail.com>
Date: Tue, 6 Jan 2026 20:04:18 +0000
Subject: [PATCH] plug-ins: Use WebPConfigLosslessPreset () for...

...lossless WEBP export
Resolves #15625

Per Daniel Plakhotich, we should use
WebPConfigLosslessPreset () when saving
lossless WEBP, so that the lossy quality settings
defined by the user don't override the lossless
values and unintentionally change the exported
file.
---
 plug-ins/file-webp/file-webp-export.c | 44 +++++++++++++++++++--------
 1 file changed, 31 insertions(+), 13 deletions(-)

diff --git a/plug-ins/file-webp/file-webp-export.c b/plug-ins/file-webp/file-webp-export.c
index b3e6edc96c..917fbe61c8 100644
--- a/plug-ins/file-webp/file-webp-export.c
+++ b/plug-ins/file-webp/file-webp-export.c
@@ -239,14 +239,22 @@ save_layer (GFile         *file,
       w = extent.width;
       h = extent.height;
 
-      /* Initialize the WebP configuration with a preset and fill in the
-       * remaining values */
-      WebPConfigPreset (&webp_config, preset, quality);
+      if (lossless)
+        {
+          WebPConfigInit (&webp_config);
+          WebPConfigLosslessPreset (&webp_config, 6);
+        }
+      else
+        {
+          /* Initialize the WebP configuration with a preset and fill in the
+           * remaining values */
+          WebPConfigPreset (&webp_config, preset, quality);
 
-      webp_config.lossless       = lossless;
-      webp_config.method         = 6;  /* better quality */
-      webp_config.alpha_quality  = alpha_quality;
-      webp_config.use_sharp_yuv  = use_sharp_yuv ? 1 : 0;
+          webp_config.lossless       = FALSE;
+          webp_config.method         = 6;  /* better quality */
+          webp_config.alpha_quality  = alpha_quality;
+          webp_config.use_sharp_yuv  = use_sharp_yuv ? 1 : 0;
+        }
 
       /* Prepare the WebP structure */
       WebPPictureInit (&picture);
@@ -708,13 +716,23 @@ save_animation (GFile         *file,
                 }
             }
 
-          WebPConfigPreset (&webp_config, preset, quality);
+          if (lossless)
+            {
+              WebPConfigInit (&webp_config);
+              WebPConfigLosslessPreset (&webp_config, 6);
+            }
+          else
+            {
+              /* Initialize the WebP configuration with a preset and fill in the
+               * remaining values */
+              WebPConfigPreset (&webp_config, preset, quality);
 
-          webp_config.lossless      = lossless;
-          webp_config.method        = 6;  /* better quality */
-          webp_config.alpha_quality = alpha_quality;
-          webp_config.exact         = 1;
-          webp_config.use_sharp_yuv = use_sharp_yuv ? 1 : 0;
+              webp_config.lossless       = FALSE;
+              webp_config.method         = 6;  /* better quality */
+              webp_config.alpha_quality  = alpha_quality;
+              webp_config.use_sharp_yuv  = use_sharp_yuv ? 1 : 0;
+            }
+          webp_config.exact = 1;
 
           WebPMemoryWriterInit (&mw);