Fixed the color grading editor in versions older than 2018.1

Author: Chman

PostProcessing/Editor/Decorators/TrackballDecorator.cs

@@ -72,8 +72,14 @@ void DrawWheel(ref Vector4 value, bool overrideState, TrackballAttribute attr)
                     s_Material = new Material(Shader.Find("Hidden/PostProcessing/Editor/Trackball")) { hideFlags = HideFlags.HideAndDontSave };
 
                 // Wheel texture
+            #if UNITY_2018_1_OR_NEWER
+                const RenderTextureReadWrite kReadWrite = RenderTextureReadWrite.sRGB;
+            #else
+                const RenderTextureReadWrite kReadWrite = RenderTextureReadWrite.Linear;
+            #endif
+
                 var oldRT = RenderTexture.active;
-                var rt = RenderTexture.GetTemporary((int)(size * scale), (int)(size * scale), 0, RenderTextureFormat.ARGB32, RenderTextureReadWrite.sRGB);
+                var rt = RenderTexture.GetTemporary((int)(size * scale), (int)(size * scale), 0, RenderTextureFormat.ARGB32, kReadWrite);
                 s_Material.SetFloat("_Offset", offset);
                 s_Material.SetFloat("_DisabledState", overrideState ? 1f : 0.5f);
                 s_Material.SetVector("_Resolution", new Vector2(size * scale, size * scale / 2f));

PostProcessing/Editor/Effects/ColorGradingEditor.cs

@@ -686,8 +686,14 @@ void DrawBackgroundTexture(Rect rect, int pass)
 
             float scale = EditorGUIUtility.pixelsPerPoint;
 
+        #if UNITY_2018_1_OR_NEWER
+            const RenderTextureReadWrite kReadWrite = RenderTextureReadWrite.sRGB;
+        #else
+            const RenderTextureReadWrite kReadWrite = RenderTextureReadWrite.Linear;
+        #endif
+
             var oldRt = RenderTexture.active;
-            var rt = RenderTexture.GetTemporary(Mathf.CeilToInt(rect.width * scale), Mathf.CeilToInt(rect.height * scale), 0, RenderTextureFormat.ARGB32, RenderTextureReadWrite.sRGB);
+            var rt = RenderTexture.GetTemporary(Mathf.CeilToInt(rect.width * scale), Mathf.CeilToInt(rect.height * scale), 0, RenderTextureFormat.ARGB32, kReadWrite);
             s_MaterialGrid.SetFloat("_DisabledState", GUI.enabled ? 1f : 0.5f);
             s_MaterialGrid.SetFloat("_PixelScaling", EditorGUIUtility.pixelsPerPoint);