From 1e67b4aa49b0abb0652e91fcffafdcae5b40e237 Mon Sep 17 00:00:00 2001
From: Cristy <urban-warrior@imagemagick.org>
Date: Sat, 9 Sep 2023 22:28:55 -0400
Subject: [PATCH] support alpha mask

---
 coders/bmp.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/coders/bmp.c b/coders/bmp.c
index 3ca1df8fe..4a6078d7d 100644
--- a/coders/bmp.c
+++ b/coders/bmp.c
@@ -75,6 +75,9 @@
 #define BI_JPEG  4
 #undef BI_PNG
 #define BI_PNG  5
+#ifndef BI_ALPHABITFIELDS
+ #define BI_ALPHABITFIELDS 6
+#endif
 #if !defined(MAGICKCORE_WINDOWS_SUPPORT) || defined(__MINGW32__)
 #undef BI_RGB
 #define BI_RGB  0
@@ -809,6 +812,13 @@ static Image *ReadBMPImage(const ImageInfo *image_info,ExceptionInfo *exception)
             bmp_info.green_mask=ReadBlobLSBLong(image);
             bmp_info.blue_mask=ReadBlobLSBLong(image);
           }
+        if ((bmp_info.size > 40) || (bmp_info.compression == BI_ALPHABITFIELDS))
+          {
+            bmp_info.red_mask=ReadBlobLSBLong(image);
+            bmp_info.green_mask=ReadBlobLSBLong(image);
+            bmp_info.blue_mask=ReadBlobLSBLong(image);
+            bmp_info.alpha_mask=ReadBlobLSBLong(image);
+          }
         if (bmp_info.size > 40)
           {
             double