From c734bfddccd7f28217b691397d3186e0aa9e2fd3 Mon Sep 17 00:00:00 2001
From: James South <james_south@hotmail.com>
Date: Tue, 10 Nov 2015 23:53:32 +1100
Subject: [PATCH] Add Compand methods to Color

This will eventually replace the PixelOperations methods.


Former-commit-id: a1058efb148c3fee54c69000698c96ade0c99c4f
Former-commit-id: 3704335fe924758d8d615ddc377f06b061308f0b
Former-commit-id: cb03cf38dab552cf2677fcfd8396f19906b80f1d
---
 src/ImageProcessor/Colors/Color.cs            | 72 +++++++++++++++++++
 .../Common/Helpers/PixelOperations.cs         |  1 +
 .../project.lock.json.REMOVED.git-id          |  2 +-
 3 files changed, 74 insertions(+), 1 deletion(-)

diff --git a/src/ImageProcessor/Colors/Color.cs b/src/ImageProcessor/Colors/Color.cs
index d85464471..62d4aef7b 100644
--- a/src/ImageProcessor/Colors/Color.cs
+++ b/src/ImageProcessor/Colors/Color.cs
@@ -473,6 +473,40 @@ namespace ImageProcessor
             return (from * (1 - amount)) + (to * amount);
         }
 
+        /// <summary>
+        /// Compresseses a linear color signal to its sRGB equivalent.
+        /// <see href="http://www.4p8.com/eric.brasseur/gamma.html#formulas"/>
+        /// <see href="http://entropymine.com/imageworsener/srgbformula/"/>
+        /// </summary>
+        /// <param name="linear">The <see cref="Color"/> whos signal to compress.</param>
+        /// <returns>The <see cref="Color"/>.</returns>
+        public static Color Compand(Color linear)
+        {
+            // TODO: Is there a faster way to do this?
+            float r = Compand(linear.R);
+            float g = Compand(linear.G);
+            float b = Compand(linear.B);
+
+            return new Color(r, g, b, linear.A);
+        }
+
+        /// <summary>
+        /// Expands an sRGB color signal to its linear equivalent.
+        /// <see href="http://www.4p8.com/eric.brasseur/gamma.html#formulas"/>
+        /// <see href="http://entropymine.com/imageworsener/srgbformula/"/>
+        /// </summary>
+        /// <param name="gamma">The <see cref="Color"/> whos signal to expand.</param>
+        /// <returns>The <see cref="Color"/>.</returns>
+        public static Color InverseCompand(Color gamma)
+        {
+            // TODO: Is there a faster way to do this?
+            float r = InverseCompand(gamma.R);
+            float g = InverseCompand(gamma.G);
+            float b = InverseCompand(gamma.B);
+
+            return new Color(r, g, b, gamma.A);
+        }
+
         /// <summary>
         /// Gets a <see cref="Vector4"/> representation for this <see cref="Color"/>.
         /// </summary>
@@ -527,6 +561,44 @@ namespace ImageProcessor
             return this.backingVector.Equals(other.backingVector);
         }
 
+        /// <summary>
+        /// Gets the compressed sRGB value from an linear signal.
+        /// <see href="http://www.4p8.com/eric.brasseur/gamma.html#formulas"/>
+        /// <see href="http://entropymine.com/imageworsener/srgbformula/"/>
+        /// </summary>
+        /// <param name="signal">The signal value to compress.</param>
+        /// <returns>
+        /// The <see cref="float"/>.
+        /// </returns>
+        private static float Compand(float signal)
+        {
+            if (signal <= 0.0031308f)
+            {
+                return signal * 12.92f;
+            }
+
+            return (1.055f * (float)Math.Pow(signal, 0.41666666f)) - 0.055f;
+        }
+
+        /// <summary>
+        /// Gets the expanded linear value from an sRGB signal.
+        /// <see href="http://www.4p8.com/eric.brasseur/gamma.html#formulas"/>
+        /// <see href="http://entropymine.com/imageworsener/srgbformula/"/>
+        /// </summary>
+        /// <param name="signal">The signal value to expand.</param>
+        /// <returns>
+        /// The <see cref="float"/>.
+        /// </returns>
+        private static float InverseCompand(float signal)
+        {
+            if (signal <= 0.04045f)
+            {
+                return signal / 12.92f;
+            }
+
+            return (float)Math.Pow((signal + 0.055f) / 1.055f, 2.4f);
+        }
+
         /// <summary>
         /// Returns the hash code for this instance.
         /// </summary>
diff --git a/src/ImageProcessor/Common/Helpers/PixelOperations.cs b/src/ImageProcessor/Common/Helpers/PixelOperations.cs
index a116c0e35..40a0fb399 100644
--- a/src/ImageProcessor/Common/Helpers/PixelOperations.cs
+++ b/src/ImageProcessor/Common/Helpers/PixelOperations.cs
@@ -6,6 +6,7 @@
 namespace ImageProcessor
 {
     using System;
+    using System.Numerics;
 
     /// <summary>
     /// Performs per-pixel operations.
diff --git a/src/ImageProcessor/project.lock.json.REMOVED.git-id b/src/ImageProcessor/project.lock.json.REMOVED.git-id
index 24339fed2..dba2656f5 100644
--- a/src/ImageProcessor/project.lock.json.REMOVED.git-id
+++ b/src/ImageProcessor/project.lock.json.REMOVED.git-id
@@ -1 +1 @@
-3f05708641eb3ed085d4689aae4a960eb067fd16
\ No newline at end of file
+eb00c54ee74016c2b70f81963e7e8f83cb2dd54b
\ No newline at end of file