From 48a36a9feb7ce7c5462a6955f27f5534b6834389 Mon Sep 17 00:00:00 2001
From: Julian Orth <ju.orth@gmail.com>
Date: Fri, 5 Sep 2025 12:34:22 +0200
Subject: [PATCH] color-management: implement gamma functions for negative
 values

---
 src/gfx_apis/vulkan/shaders/transfer_functions.glsl | 12 ++++++------
 src/theme.rs                                        | 12 ++++++------
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/src/gfx_apis/vulkan/shaders/transfer_functions.glsl b/src/gfx_apis/vulkan/shaders/transfer_functions.glsl
index 88236152..3ffdf35f 100644
--- a/src/gfx_apis/vulkan/shaders/transfer_functions.glsl
+++ b/src/gfx_apis/vulkan/shaders/transfer_functions.glsl
@@ -129,9 +129,9 @@ vec3 apply_eotf(vec3 c) {
         case TF_SRGB: return eotf_srgb(c);
         case TF_LINEAR: return c;
         case TF_ST2084_PQ: return eotf_st2084_pq(c);
-        case TF_GAMMA24: return pow(max(c, 0.0), vec3(2.4));
-        case TF_GAMMA22: return pow(max(c, 0.0), vec3(2.2));
-        case TF_GAMMA28: return pow(max(c, 0.0), vec3(2.8));
+        case TF_GAMMA24: return sign(c) * pow(abs(c), vec3(2.4));
+        case TF_GAMMA22: return sign(c) * pow(abs(c), vec3(2.2));
+        case TF_GAMMA28: return sign(c) * pow(abs(c), vec3(2.8));
         case TF_ST240: return eotf_st240(c);
         case TF_EXT_SRGB: return eotf_ext_srgb(c);
         case TF_LOG100: return eotf_log100(c);
@@ -146,9 +146,9 @@ vec3 apply_oetf(vec3 c) {
         case TF_SRGB: return oetf_srgb(c);
         case TF_LINEAR: return c;
         case TF_ST2084_PQ: return oetf_st2084_pq(c);
-        case TF_GAMMA24: return pow(max(c, 0.0), vec3(1.0 / 2.4));
-        case TF_GAMMA22: return pow(max(c, 0.0), vec3(1.0 / 2.2));
-        case TF_GAMMA28: return pow(max(c, 0.0), vec3(1.0 / 2.8));
+        case TF_GAMMA24: return sign(c) * pow(abs(c), vec3(1.0 / 2.4));
+        case TF_GAMMA22: return sign(c) * pow(abs(c), vec3(1.0 / 2.2));
+        case TF_GAMMA28: return sign(c) * pow(abs(c), vec3(1.0 / 2.8));
         case TF_ST240: return oetf_st240(c);
         case TF_EXT_SRGB: return oetf_ext_srgb(c);
         case TF_LOG100: return oetf_log100(c);
diff --git a/src/theme.rs b/src/theme.rs
index 23ff6cf2..e6c249fd 100644
--- a/src/theme.rs
+++ b/src/theme.rs
@@ -113,13 +113,13 @@ impl Color {
             c.powf(2.6) * 52.37 / 48.0
         }
         fn gamma22(c: f32) -> f32 {
-            c.powf(2.2)
+            c.signum() * c.abs().powf(2.2)
         }
         fn gamma24(c: f32) -> f32 {
-            c.powf(2.4)
+            c.signum() * c.abs().powf(2.4)
         }
         fn gamma28(c: f32) -> f32 {
-            c.powf(2.8)
+            c.signum() * c.abs().powf(2.8)
         }
         macro_rules! convert {
             ($tf:ident) => {{
@@ -274,13 +274,13 @@ impl Color {
             (48.0 * c / 52.37).powf(1.0 / 2.6)
         }
         fn gamma22(c: f32) -> f32 {
-            c.powf(1.0 / 2.2)
+            c.signum() * c.abs().powf(1.0 / 2.2)
         }
         fn gamma24(c: f32) -> f32 {
-            c.powf(1.0 / 2.4)
+            c.signum() * c.abs().powf(1.0 / 2.4)
         }
         fn gamma28(c: f32) -> f32 {
-            c.powf(1.0 / 2.8)
+            c.signum() * c.abs().powf(1.0 / 2.8)
         }
         macro_rules! convert {
             ($tf:ident) => {{