From 4e9b7e61a7a2e42b2b56c699d10dece83089e0c0 Mon Sep 17 00:00:00 2001
From: lightningterror <18107717+lightningterror@users.noreply.github.com>
Date: Tue, 21 Feb 2023 17:37:29 +0100
Subject: [PATCH] GS-ogl: Check each channel individually if it overflows and
 do corrections.

---
 bin/resources/shaders/opengl/tfx_fs.glsl | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/bin/resources/shaders/opengl/tfx_fs.glsl b/bin/resources/shaders/opengl/tfx_fs.glsl
index 9bb657db39..b2029da798 100644
--- a/bin/resources/shaders/opengl/tfx_fs.glsl
+++ b/bin/resources/shaders/opengl/tfx_fs.glsl
@@ -686,8 +686,10 @@ void ps_color_clamp_wrap(inout vec3 C)
 #endif
 }
 
-void ps_blend(inout vec4 Color, inout float As)
+void ps_blend(inout vec4 Color, inout vec4 As_rgba)
 {
+float As = As_rgba.a;
+
 #if SW_BLEND
 
     // PABE
@@ -768,16 +770,15 @@ void ps_blend(inout vec4 Color, inout float As)
 #if PS_CLR_HW == 1
     // Replace Af with As so we can do proper compensation for Alpha.
 #if PS_BLEND_C == 2
-    As = Af;
+    As_rgba = vec4(Af);
 #endif
     // Subtract 1 for alpha to compensate for the changed equation,
     // if c.rgb > 255.0f then we further need to adjust alpha accordingly,
     // we pick the lowest overflow from all colors because it's the safest,
     // we divide by 255 the color because we don't know Cd value,
     // changed alpha should only be done for hw blend.
-    float min_color = min(min(Color.r, Color.g), Color.b);
-    float alpha_compensate = max(1.0f, min_color / 255.0f);
-    As -= alpha_compensate;
+    vec3 alpha_compensate = max(vec3(1.0f), Color.rgb / vec3(255.0f));
+    As_rgba.rgb -= alpha_compensate;
 #elif PS_CLR_HW == 2
     // Compensate slightly for Cd*(As + 1) - Cs*As.
     // The initial factor we chose is 1 (0.00392)
@@ -927,9 +928,9 @@ void ps_main()
 
 #if SW_AD_TO_HW
     vec4 RT = trunc(fetch_rt() * 255.0f + 0.1f);
-    float alpha_blend = RT.a / 128.0f;
+    vec4 alpha_blend = vec4(RT.a / 128.0f);
 #else
-    float alpha_blend = C.a / 128.0f;
+    vec4 alpha_blend = vec4(C.a / 128.0f);
 #endif
 
     // Correct the ALPHA value based on the output format
@@ -969,12 +970,12 @@ void ps_main()
     SV_Target0 = C / 255.0f;
 #endif
 #if !defined(DISABLE_DUAL_SOURCE) && !PS_NO_COLOR1
-    SV_Target1 = vec4(alpha_blend);
+    SV_Target1 = alpha_blend;
 #endif
 
 #if PS_NO_ABLEND
     // write alpha blend factor into col0
-    SV_Target0.a = alpha_blend;
+    SV_Target0.a = alpha_blend.a;
 #endif
 #if PS_ONLY_ALPHA
     // rgb isn't used