1 files changed, 30 insertions, 0 deletions
diff --git a/source/blender/compositor/operations/COM_AlphaOverKeyOperation.cc b/source/blender/compositor/operations/COM_AlphaOverKeyOperation.cc
index 0c656753a51..30e7fab4027 100644
--- a/source/blender/compositor/operations/COM_AlphaOverKeyOperation.cc
+++ b/source/blender/compositor/operations/COM_AlphaOverKeyOperation.cc
@@ -20,6 +20,11 @@
 
 namespace blender::compositor {
 
+AlphaOverKeyOperation::AlphaOverKeyOperation()
+{
+  this->flags.can_be_constant = true;
+}
+
 void AlphaOverKeyOperation::executePixelSampled(float output[4],
                                                 float x,
                                                 float y,
@@ -50,4 +55,29 @@ void AlphaOverKeyOperation::executePixelSampled(float output[4],
   }
 }
 
+void AlphaOverKeyOperation::update_memory_buffer_row(PixelCursor &p)
+{
+  for (; p.out < p.row_end; p.next()) {
+    const float *color1 = p.color1;
+    const float *over_color = p.color2;
+    const float value = *p.value;
+
+    if (over_color[3] <= 0.0f) {
+      copy_v4_v4(p.out, color1);
+    }
+    else if (value == 1.0f && over_color[3] >= 1.0f) {
+      copy_v4_v4(p.out, over_color);
+    }
+    else {
+      const float premul = value * over_color[3];
+      const float mul = 1.0f - premul;
+
+      p.out[0] = (mul * color1[0]) + premul * over_color[0];
+      p.out[1] = (mul * color1[1]) + premul * over_color[1];
+      p.out[2] = (mul * color1[2]) + premul * over_color[2];
+      p.out[3] = (mul * color1[3]) + value * over_color[3];
+    }
+  }
+}
+
 }  // namespace blender::compositor