https://imagemagick.org/discourse-server/viewtopic.php?f=3&t=34675

diff --git a/MagickCore/composite.c b/MagickCore/composite.c
index d1351ed9ed2c78f1f7a84247bb5244c560d03a9b..25b43670d81e64d9f4d830828d7d007226ed91cd 100644 (file)
--- a/MagickCore/composite.c
+++ b/MagickCore/composite.c
@@ -2262,7 +2262,7 @@ MagickExport MagickBooleanType CompositeImage(Image *image,
           }
           case StereoCompositeOp:
           {
-            if ((channel == GreenPixelChannel) || (channel == BluePixelChannel))
+            if (channel == RedPixelChannel)
               pixel=(MagickRealType) GetPixelRed(source_image,p);
             break;
           }