From bbe3917ed18fa164dd31a0f3bfcc9d4362b8f545 Mon Sep 17 00:00:00 2001
From: Keuin <keuinx@gmail.com>
Date: Thu, 14 Apr 2022 15:03:16 +0800
Subject: Specialize pixel::gamma2 for small values.

---
 bitmap.h | 29 ++++++++++++++++++++++++-----
 1 file changed, 24 insertions(+), 5 deletions(-)

diff --git a/bitmap.h b/bitmap.h
index 58b9a25..c955803 100644
--- a/bitmap.h
+++ b/bitmap.h
@@ -72,15 +72,34 @@ struct pixel {
         return mod; // FIXME
     }
 
-    inline pixel<T> gamma2() const {
+    pixel<T> gamma2() const {
         const auto max = max_value();
-        const double r_ = sqrt(1.0 * this->r / max);
-        const double g_ = sqrt(1.0 * this->g / max);
-        const double b_ = sqrt(1.0 * this->b / max);
-        return pixel<T>::from_normalized(r_, g_, b_);
+        if (sizeof(T) <= 2) {
+            // 26% faster than using double
+            const auto r_ = sqrtf((float) (this->r) / (float) max);
+            const auto g_ = sqrtf((float) (this->g) / (float) max);
+            const auto b_ = sqrtf((float) (this->b) / (float) max);
+            return pixel<T>::from_normalized(r_, g_, b_);
+        } else {
+            const auto r_ = sqrt(1.0 * this->r / max);
+            const auto g_ = sqrt(1.0 * this->g / max);
+            const auto b_ = sqrt(1.0 * this->b / max);
+            return pixel<T>::from_normalized(r_, g_, b_);
+        }
     }
+
 };
 
+//template<>
+//pixel<uint16_t> pixel<uint16_t>::gamma2() const {
+//    // 26% faster than using double
+//    const auto max = max_value();
+//    const auto r_ = sqrtf((float) (this->r) / (float) (max));
+//    const auto g_ = sqrtf((float) (this->g) / (float) (max));
+//    const auto b_ = sqrtf((float) (this->b) / (float) (max));
+//    return pixel<uint16_t>::from_normalized(r_, g_, b_);
+//}
+
 template<
         typename T,
         typename S,
-- 
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