From 94ceabacf03c8fc04ff71a4199e8d1db2710dcfd Mon Sep 17 00:00:00 2001
From: itsmeow <itsmeow@itsmeow.dev>
Date: Mon, 1 Jan 2024 01:23:26 -0500
Subject: [PATCH] Don't multiply alpha when blending onto a transparent pixel
 (#1577)

---
 OpenDreamRuntime/Objects/DreamIcon.cs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/OpenDreamRuntime/Objects/DreamIcon.cs b/OpenDreamRuntime/Objects/DreamIcon.cs
index ec954527c9..4d8320433c 100644
--- a/OpenDreamRuntime/Objects/DreamIcon.cs
+++ b/OpenDreamRuntime/Objects/DreamIcon.cs
@@ -333,6 +333,14 @@ protected void BlendPixel(Rgba32[] pixels, int dstPixelPosition, Rgba32 src) {
             }
 
             case BlendType.Overlay: {
+                // When overlaying onto 0 alpha, don't multiply the RGB values by alpha.
+                if (dst.A == 0) {
+                    pixels[dstPixelPosition].R = src.R;
+                    pixels[dstPixelPosition].G = src.G;
+                    pixels[dstPixelPosition].B = src.B;
+                    pixels[dstPixelPosition].A = src.A;
+                    break;
+                }
                 pixels[dstPixelPosition].R = (byte) (dst.R + (src.R - dst.R) * src.A / 255);
                 pixels[dstPixelPosition].G = (byte) (dst.G + (src.G - dst.G) * src.A / 255);
                 pixels[dstPixelPosition].B = (byte) (dst.B + (src.B - dst.B) * src.A / 255);