From c956901a375167a1bb8b9167916a98b9a1a0a7b8 Mon Sep 17 00:00:00 2001
From: GenevensiS <66968533+G-e-n-e-v-e-n-s-i-S@users.noreply.github.com>
Date: Tue, 17 Sep 2024 10:01:21 +0200
Subject: [PATCH] make combine_blend function blend alpha channels as well

---
 src/gfx/combine_image.cpp | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/gfx/combine_image.cpp b/src/gfx/combine_image.cpp
index 65edcd49..a1e2ff96 100644
--- a/src/gfx/combine_image.cpp
+++ b/src/gfx/combine_image.cpp
@@ -91,11 +91,17 @@ COMBINE_FUN(COMBINE_SYMMETRIC_OVERLAY, (Combine<COMBINE_OVERLAY>::f(a,b) + Combi
 /// The results are stored in the image A.
 template <ImageCombine combine>
 void combine_image_do(Image& a, Image b) {
-  UInt size = a.GetWidth() * a.GetHeight() * 3;
+  UInt size = a.GetWidth() * a.GetHeight();
   Byte *dataA = a.GetData(), *dataB = b.GetData();
   // for each pixel: apply function
-  for (UInt i = 0 ; i < size ; ++i) {
+  for (UInt i = 0 ; i < (size * 3); ++i) {
     dataA[i] = Combine<combine>::f(dataA[i], dataB[i]);
+  }
+  if (a.HasAlpha() && b.HasAlpha()) {
+    Byte* alphaA = a.GetAlpha(), * alphaB = b.GetAlpha();
+    for (UInt i = 0; i < size; ++i) {
+      alphaA[i] = Combine<combine>::f(alphaA[i], alphaB[i]);
+    }
   }
 }